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// ignore-tidy-filelength
use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
use crate::ast::{GenericBound, TraitBoundModifier};
use crate::ast::Unsafety;
use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
use crate::ast::Block;
use crate::ast::{BlockCheckMode, CaptureBy, Movability};
use crate::ast::{Constness, Crate};
use crate::ast::Defaultness;
use crate::ast::EnumDef;
use crate::ast::{Expr, ExprKind, RangeLimits};
use crate::ast::{Field, FnDecl, FnHeader};
use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
use crate::ast::{GenericParam, GenericParamKind};
use crate::ast::GenericArg;
use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
use crate::ast::{Label, Lifetime};
use crate::ast::Local;
use crate::ast::MacStmtStyle;
use crate::ast::{Mac, Mac_, MacDelimiter};
use crate::ast::{MutTy, Mutability};
use crate::ast::{Pat, PatKind, PathSegment};
use crate::ast::{PolyTraitRef, QSelf};
use crate::ast::{Stmt, StmtKind};
use crate::ast::{VariantData, StructField};
use crate::ast::StrStyle;
use crate::ast::SelfKind;
use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
use crate::ast::{Ty, TyKind, AssocTyConstraint, AssocTyConstraintKind, GenericBounds};
use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
use crate::ast::{UseTree, UseTreeKind};
use crate::ast::{BinOpKind, UnOp};
use crate::ast::{RangeEnd, RangeSyntax};
use crate::{ast, attr};
use crate::ext::base::DummyResult;
use crate::ext::hygiene::SyntaxContext;
use crate::source_map::{self, SourceMap, Spanned, respan};
use crate::parse::{SeqSep, classify, literal, token};
use crate::parse::lexer::UnmatchedBrace;
use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
use crate::parse::token::{Token, TokenKind, DelimToken};
use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
use crate::util::parser::{AssocOp, Fixity};
use crate::print::pprust;
use crate::ptr::P;
use crate::parse::PResult;
use crate::ThinVec;
use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
use crate::symbol::{kw, sym, Symbol};
use crate::parse::diagnostics::{Error, dummy_arg};
use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
use rustc_target::spec::abi::{self, Abi};
use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
use log::debug;
use std::borrow::Cow;
use std::cmp;
use std::mem;
use std::path::{self, Path, PathBuf};
use std::slice;
#[derive(Debug)]
/// Whether the type alias or associated type is a concrete type or an existential type
pub enum AliasKind {
/// Just a new name for the same type
Weak(P<Ty>),
/// Only trait impls of the type will be usable, not the actual type itself
Existential(GenericBounds),
}
bitflags::bitflags! {
struct Restrictions: u8 {
const STMT_EXPR = 1 << 0;
const NO_STRUCT_LITERAL = 1 << 1;
}
}
type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
/// Specifies how to parse a path.
#[derive(Copy, Clone, PartialEq)]
pub enum PathStyle {
/// In some contexts, notably in expressions, paths with generic arguments are ambiguous
/// with something else. For example, in expressions `segment < ....` can be interpreted
/// as a comparison and `segment ( ....` can be interpreted as a function call.
/// In all such contexts the non-path interpretation is preferred by default for practical
/// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
/// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
Expr,
/// In other contexts, notably in types, no ambiguity exists and paths can be written
/// without the disambiguator, e.g., `x<y>` - unambiguously a path.
/// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
Type,
/// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
/// visibilities or attributes.
/// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
/// (paths in "mod" contexts have to be checked later for absence of generic arguments
/// anyway, due to macros), but it is used to avoid weird suggestions about expected
/// tokens when something goes wrong.
Mod,
}
#[derive(Clone, Copy, PartialEq, Debug)]
crate enum SemiColonMode {
Break,
Ignore,
Comma,
}
#[derive(Clone, Copy, PartialEq, Debug)]
crate enum BlockMode {
Break,
Ignore,
}
/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
/// dropped into the token stream, which happens while parsing the result of
/// macro expansion). Placement of these is not as complex as I feared it would
/// be. The important thing is to make sure that lookahead doesn't balk at
/// `token::Interpolated` tokens.
macro_rules! maybe_whole_expr {
($p:expr) => {
if let token::Interpolated(nt) = &$p.token.kind {
match &**nt {
token::NtExpr(e) | token::NtLiteral(e) => {
let e = e.clone();
$p.bump();
return Ok(e);
}
token::NtPath(path) => {
let path = path.clone();
$p.bump();
return Ok($p.mk_expr(
$p.token.span, ExprKind::Path(None, path), ThinVec::new()
));
}
token::NtBlock(block) => {
let block = block.clone();
$p.bump();
return Ok($p.mk_expr(
$p.token.span, ExprKind::Block(block, None), ThinVec::new()
));
}
_ => {},
};
}
}
}
/// As maybe_whole_expr, but for things other than expressions
macro_rules! maybe_whole {
($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
if let token::Interpolated(nt) = &$p.token.kind {
if let token::$constructor(x) = &**nt {
let $x = x.clone();
$p.bump();
return Ok($e);
}
}
};
}
/// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
macro_rules! maybe_recover_from_interpolated_ty_qpath {
($self: expr, $allow_qpath_recovery: expr) => {
if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
if let token::Interpolated(nt) = &$self.token.kind {
if let token::NtTy(ty) = &**nt {
let ty = ty.clone();
$self.bump();
return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
}
}
}
}
}
fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
if let Some(ref mut rhs) = rhs {
lhs.append(rhs);
}
lhs
}
#[derive(Debug, Clone, Copy, PartialEq)]
enum PrevTokenKind {
DocComment,
Comma,
Plus,
Interpolated,
Eof,
Ident,
BitOr,
Other,
}
// NOTE: `Ident`s are handled by `common.rs`.
#[derive(Clone)]
pub struct Parser<'a> {
pub sess: &'a ParseSess,
/// The current normalized token.
/// "Normalized" means that some interpolated tokens
/// (`$i: ident` and `$l: lifetime` meta-variables) are replaced
/// with non-interpolated identifier and lifetime tokens they refer to.
/// Perhaps the normalized / non-normalized setup can be simplified somehow.
pub token: Token,
/// Span of the current non-normalized token.
meta_var_span: Option<Span>,
/// Span of the previous non-normalized token.
pub prev_span: Span,
/// Kind of the previous normalized token (in simplified form).
prev_token_kind: PrevTokenKind,
restrictions: Restrictions,
/// Used to determine the path to externally loaded source files.
crate directory: Directory<'a>,
/// `true` to parse sub-modules in other files.
pub recurse_into_file_modules: bool,
/// Name of the root module this parser originated from. If `None`, then the
/// name is not known. This does not change while the parser is descending
/// into modules, and sub-parsers have new values for this name.
pub root_module_name: Option<String>,
crate expected_tokens: Vec<TokenType>,
crate token_cursor: TokenCursor,
desugar_doc_comments: bool,
/// `true` we should configure out of line modules as we parse.
pub cfg_mods: bool,
/// This field is used to keep track of how many left angle brackets we have seen. This is
/// required in order to detect extra leading left angle brackets (`<` characters) and error
/// appropriately.
///
/// See the comments in the `parse_path_segment` function for more details.
crate unmatched_angle_bracket_count: u32,
crate max_angle_bracket_count: u32,
/// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
/// it gets removed from here. Every entry left at the end gets emitted as an independent
/// error.
crate unclosed_delims: Vec<UnmatchedBrace>,
crate last_unexpected_token_span: Option<Span>,
/// If present, this `Parser` is not parsing Rust code but rather a macro call.
crate subparser_name: Option<&'static str>,
}
impl<'a> Drop for Parser<'a> {
fn drop(&mut self) {
let diag = self.diagnostic();
emit_unclosed_delims(&mut self.unclosed_delims, diag);
}
}
#[derive(Clone)]
crate struct TokenCursor {
crate frame: TokenCursorFrame,
crate stack: Vec<TokenCursorFrame>,
}
#[derive(Clone)]
crate struct TokenCursorFrame {
crate delim: token::DelimToken,
crate span: DelimSpan,
crate open_delim: bool,
crate tree_cursor: tokenstream::Cursor,
crate close_delim: bool,
crate last_token: LastToken,
}
/// This is used in `TokenCursorFrame` above to track tokens that are consumed
/// by the parser, and then that's transitively used to record the tokens that
/// each parse AST item is created with.
///
/// Right now this has two states, either collecting tokens or not collecting
/// tokens. If we're collecting tokens we just save everything off into a local
/// `Vec`. This should eventually though likely save tokens from the original
/// token stream and just use slicing of token streams to avoid creation of a
/// whole new vector.
///
/// The second state is where we're passively not recording tokens, but the last
/// token is still tracked for when we want to start recording tokens. This
/// "last token" means that when we start recording tokens we'll want to ensure
/// that this, the first token, is included in the output.
///
/// You can find some more example usage of this in the `collect_tokens` method
/// on the parser.
#[derive(Clone)]
crate enum LastToken {
Collecting(Vec<TreeAndJoint>),
Was(Option<TreeAndJoint>),
}
impl TokenCursorFrame {
fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
TokenCursorFrame {
delim: delim,
span: sp,
open_delim: delim == token::NoDelim,
tree_cursor: tts.clone().into_trees(),
close_delim: delim == token::NoDelim,
last_token: LastToken::Was(None),
}
}
}
impl TokenCursor {
fn next(&mut self) -> Token {
loop {
let tree = if !self.frame.open_delim {
self.frame.open_delim = true;
TokenTree::open_tt(self.frame.span.open, self.frame.delim)
} else if let Some(tree) = self.frame.tree_cursor.next() {
tree
} else if !self.frame.close_delim {
self.frame.close_delim = true;
TokenTree::close_tt(self.frame.span.close, self.frame.delim)
} else if let Some(frame) = self.stack.pop() {
self.frame = frame;
continue
} else {
return Token::new(token::Eof, DUMMY_SP);
};
match self.frame.last_token {
LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
}
match tree {
TokenTree::Token(token) => return token,
TokenTree::Delimited(sp, delim, tts) => {
let frame = TokenCursorFrame::new(sp, delim, &tts);
self.stack.push(mem::replace(&mut self.frame, frame));
}
}
}
}
fn next_desugared(&mut self) -> Token {
let (name, sp) = match self.next() {
Token { kind: token::DocComment(name), span } => (name, span),
tok => return tok,
};
let stripped = strip_doc_comment_decoration(&name.as_str());
// Searches for the occurrences of `"#*` and returns the minimum number of `#`s
// required to wrap the text.
let mut num_of_hashes = 0;
let mut count = 0;
for ch in stripped.chars() {
count = match ch {
'"' => 1,
'#' if count > 0 => count + 1,
_ => 0,
};
num_of_hashes = cmp::max(num_of_hashes, count);
}
let delim_span = DelimSpan::from_single(sp);
let body = TokenTree::Delimited(
delim_span,
token::Bracket,
[
TokenTree::token(token::Ident(sym::doc, false), sp),
TokenTree::token(token::Eq, sp),
TokenTree::token(TokenKind::lit(
token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None
), sp),
]
.iter().cloned().collect::<TokenStream>().into(),
);
self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
delim_span,
token::NoDelim,
&if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
[TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
.iter().cloned().collect::<TokenStream>().into()
} else {
[TokenTree::token(token::Pound, sp), body]
.iter().cloned().collect::<TokenStream>().into()
},
)));
self.next()
}
}
#[derive(Clone, PartialEq)]
crate enum TokenType {
Token(TokenKind),
Keyword(Symbol),
Operator,
Lifetime,
Ident,
Path,
Type,
Const,
}
impl TokenType {
crate fn to_string(&self) -> String {
match *self {
TokenType::Token(ref t) => format!("`{}`", pprust::token_kind_to_string(t)),
TokenType::Keyword(kw) => format!("`{}`", kw),
TokenType::Operator => "an operator".to_string(),
TokenType::Lifetime => "lifetime".to_string(),
TokenType::Ident => "identifier".to_string(),
TokenType::Path => "path".to_string(),
TokenType::Type => "type".to_string(),
TokenType::Const => "const".to_string(),
}
}
}
/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
/// `IDENT<<u8 as Trait>::AssocTy>`.
///
/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
/// that `IDENT` is not the ident of a fn trait.
fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
t == &token::ModSep || t == &token::Lt ||
t == &token::BinOp(token::Shl)
}
/// Information about the path to a module.
pub struct ModulePath {
name: String,
path_exists: bool,
pub result: Result<ModulePathSuccess, Error>,
}
pub struct ModulePathSuccess {
pub path: PathBuf,
pub directory_ownership: DirectoryOwnership,
warn: bool,
}
#[derive(Debug)]
enum LhsExpr {
NotYetParsed,
AttributesParsed(ThinVec<Attribute>),
AlreadyParsed(P<Expr>),
}
impl From<Option<ThinVec<Attribute>>> for LhsExpr {
fn from(o: Option<ThinVec<Attribute>>) -> Self {
if let Some(attrs) = o {
LhsExpr::AttributesParsed(attrs)
} else {
LhsExpr::NotYetParsed
}
}
}
impl From<P<Expr>> for LhsExpr {
fn from(expr: P<Expr>) -> Self {
LhsExpr::AlreadyParsed(expr)
}
}
#[derive(Copy, Clone, Debug)]
crate enum TokenExpectType {
Expect,
NoExpect,
}
impl<'a> Parser<'a> {
pub fn new(
sess: &'a ParseSess,
tokens: TokenStream,
directory: Option<Directory<'a>>,
recurse_into_file_modules: bool,
desugar_doc_comments: bool,
subparser_name: Option<&'static str>,
) -> Self {
let mut parser = Parser {
sess,
token: Token::dummy(),
prev_span: DUMMY_SP,
meta_var_span: None,
prev_token_kind: PrevTokenKind::Other,
restrictions: Restrictions::empty(),
recurse_into_file_modules,
directory: Directory {
path: Cow::from(PathBuf::new()),
ownership: DirectoryOwnership::Owned { relative: None }
},
root_module_name: None,
expected_tokens: Vec::new(),
token_cursor: TokenCursor {
frame: TokenCursorFrame::new(
DelimSpan::dummy(),
token::NoDelim,
&tokens.into(),
),
stack: Vec::new(),
},
desugar_doc_comments,
cfg_mods: true,
unmatched_angle_bracket_count: 0,
max_angle_bracket_count: 0,
unclosed_delims: Vec::new(),
last_unexpected_token_span: None,
subparser_name,
};
parser.token = parser.next_tok();
if let Some(directory) = directory {
parser.directory = directory;
} else if !parser.token.span.is_dummy() {
if let FileName::Real(mut path) =
sess.source_map().span_to_unmapped_path(parser.token.span) {
path.pop();
parser.directory.path = Cow::from(path);
}
}
parser.process_potential_macro_variable();
parser
}
fn next_tok(&mut self) -> Token {
let mut next = if self.desugar_doc_comments {
self.token_cursor.next_desugared()
} else {
self.token_cursor.next()
};
if next.span.is_dummy() {
// Tweak the location for better diagnostics, but keep syntactic context intact.
next.span = self.prev_span.with_ctxt(next.span.ctxt());
}
next
}
/// Converts the current token to a string using `self`'s reader.
pub fn this_token_to_string(&self) -> String {
pprust::token_to_string(&self.token)
}
crate fn token_descr(&self) -> Option<&'static str> {
Some(match &self.token.kind {
_ if self.token.is_special_ident() => "reserved identifier",
_ if self.token.is_used_keyword() => "keyword",
_ if self.token.is_unused_keyword() => "reserved keyword",
token::DocComment(..) => "doc comment",
_ => return None,
})
}
crate fn this_token_descr(&self) -> String {
if let Some(prefix) = self.token_descr() {
format!("{} `{}`", prefix, self.this_token_to_string())
} else {
format!("`{}`", self.this_token_to_string())
}
}
crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
match self.expect_one_of(&[], &[]) {
Err(e) => Err(e),
Ok(_) => unreachable!(),
}
}
/// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
if self.expected_tokens.is_empty() {
if self.token == *t {
self.bump();
Ok(false)
} else {
self.unexpected_try_recover(t)
}
} else {
self.expect_one_of(slice::from_ref(t), &[])
}
}
/// Expect next token to be edible or inedible token. If edible,
/// then consume it; if inedible, then return without consuming
/// anything. Signal a fatal error if next token is unexpected.
pub fn expect_one_of(
&mut self,
edible: &[TokenKind],
inedible: &[TokenKind],
) -> PResult<'a, bool /* recovered */> {
if edible.contains(&self.token.kind) {
self.bump();
Ok(false)
} else if inedible.contains(&self.token.kind) {
// leave it in the input
Ok(false)
} else if self.last_unexpected_token_span == Some(self.token.span) {
FatalError.raise();
} else {
self.expected_one_of_not_found(edible, inedible)
}
}
/// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
fn interpolated_or_expr_span(
&self,
expr: PResult<'a, P<Expr>>,
) -> PResult<'a, (Span, P<Expr>)> {
expr.map(|e| {
if self.prev_token_kind == PrevTokenKind::Interpolated {
(self.prev_span, e)
} else {
(e.span, e)
}
})
}
pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
self.parse_ident_common(true)
}
fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
match self.token.kind {
token::Ident(name, _) => {
if self.token.is_reserved_ident() {
let mut err = self.expected_ident_found();
if recover {
err.emit();
} else {
return Err(err);
}
}
let span = self.token.span;
self.bump();
Ok(Ident::new(name, span))
}
_ => {
Err(if self.prev_token_kind == PrevTokenKind::DocComment {
self.span_fatal_err(self.prev_span, Error::UselessDocComment)
} else {
self.expected_ident_found()
})
}
}
}
/// Checks if the next token is `tok`, and returns `true` if so.
///
/// This method will automatically add `tok` to `expected_tokens` if `tok` is not
/// encountered.
crate fn check(&mut self, tok: &TokenKind) -> bool {
let is_present = self.token == *tok;
if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
is_present
}
/// Consumes a token 'tok' if it exists. Returns whether the given token was present.
pub fn eat(&mut self, tok: &TokenKind) -> bool {
let is_present = self.check(tok);
if is_present { self.bump() }
is_present
}
fn check_keyword(&mut self, kw: Symbol) -> bool {
self.expected_tokens.push(TokenType::Keyword(kw));
self.token.is_keyword(kw)
}
/// If the next token is the given keyword, eats it and returns
/// `true`. Otherwise, returns `false`.
pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
if self.check_keyword(kw) {
self.bump();
true
} else {
false
}
}
fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
if self.token.is_keyword(kw) {
self.bump();
true
} else {
false
}
}
/// If the given word is not a keyword, signals an error.
/// If the next token is not the given word, signals an error.
/// Otherwise, eats it.
fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
if !self.eat_keyword(kw) {
self.unexpected()
} else {
Ok(())
}
}
crate fn check_ident(&mut self) -> bool {
if self.token.is_ident() {
true
} else {
self.expected_tokens.push(TokenType::Ident);
false
}
}
fn check_path(&mut self) -> bool {
if self.token.is_path_start() {
true
} else {
self.expected_tokens.push(TokenType::Path);
false
}
}
fn check_type(&mut self) -> bool {
if self.token.can_begin_type() {
true
} else {
self.expected_tokens.push(TokenType::Type);
false
}
}
fn check_const_arg(&mut self) -> bool {
if self.token.can_begin_const_arg() {
true
} else {
self.expected_tokens.push(TokenType::Const);
false
}
}
/// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
/// and continues. If a `+` is not seen, returns `false`.
///
/// This is used when token-splitting `+=` into `+`.
/// See issue #47856 for an example of when this may occur.
fn eat_plus(&mut self) -> bool {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
match self.token.kind {
token::BinOp(token::Plus) => {
self.bump();
true
}
token::BinOpEq(token::Plus) => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
self.bump_with(token::Eq, span);
true
}
_ => false,
}
}
/// Checks to see if the next token is either `+` or `+=`.
/// Otherwise returns `false`.
fn check_plus(&mut self) -> bool {
if self.token.is_like_plus() {
true
}
else {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
false
}
}
/// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
/// `&` and continues. If an `&` is not seen, signals an error.
fn expect_and(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
match self.token.kind {
token::BinOp(token::And) => {
self.bump();
Ok(())
}
token::AndAnd => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::And), span))
}
_ => self.unexpected()
}
}
/// Expects and consumes an `|`. If `||` is seen, replaces it with a single
/// `|` and continues. If an `|` is not seen, signals an error.
fn expect_or(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
match self.token.kind {
token::BinOp(token::Or) => {
self.bump();
Ok(())
}
token::OrOr => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
Ok(self.bump_with(token::BinOp(token::Or), span))
}
_ => self.unexpected()
}
}
fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
}
/// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
/// `<` and continue. If `<-` is seen, replaces it with a single `<`
/// and continue. If a `<` is not seen, returns false.
///
/// This is meant to be used when parsing generics on a path to get the
/// starting token.
fn eat_lt(&mut self) -> bool {
self.expected_tokens.push(TokenType::Token(token::Lt));
let ate = match self.token.kind {
token::Lt => {
self.bump();
true
}
token::BinOp(token::Shl) => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
self.bump_with(token::Lt, span);
true
}
token::LArrow => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
self.bump_with(token::BinOp(token::Minus), span);
true
}
_ => false,
};
if ate {
// See doc comment for `unmatched_angle_bracket_count`.
self.unmatched_angle_bracket_count += 1;
self.max_angle_bracket_count += 1;
debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
}
ate
}
fn expect_lt(&mut self) -> PResult<'a, ()> {
if !self.eat_lt() {
self.unexpected()
} else {
Ok(())
}
}
/// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
/// with a single `>` and continues. If a `>` is not seen, signals an error.
fn expect_gt(&mut self) -> PResult<'a, ()> {
self.expected_tokens.push(TokenType::Token(token::Gt));
let ate = match self.token.kind {
token::Gt => {
self.bump();
Some(())
}
token::BinOp(token::Shr) => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
Some(self.bump_with(token::Gt, span))
}
token::BinOpEq(token::Shr) => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
Some(self.bump_with(token::Ge, span))
}
token::Ge => {
let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
Some(self.bump_with(token::Eq, span))
}
_ => None,
};
match ate {
Some(_) => {
// See doc comment for `unmatched_angle_bracket_count`.
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
Ok(())
},
None => self.unexpected(),
}
}
/// Parses a sequence, including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_end<T, F>(&mut self,
ket: &TokenKind,
sep: SeqSep,
f: F)
-> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
if !recovered {
self.bump();
}
Ok(val)
}
/// Parses a sequence, not including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
pub fn parse_seq_to_before_end<T, F>(
&mut self,
ket: &TokenKind,
sep: SeqSep,
f: F,
) -> PResult<'a, (Vec<T>, bool)>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
}
crate fn parse_seq_to_before_tokens<T, F>(
&mut self,
kets: &[&TokenKind],
sep: SeqSep,
expect: TokenExpectType,
mut f: F,
) -> PResult<'a, (Vec<T>, bool /* recovered */)>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
let mut first = true;
let mut recovered = false;
let mut v = vec![];
while !kets.iter().any(|k| {
match expect {
TokenExpectType::Expect => self.check(k),
TokenExpectType::NoExpect => self.token == **k,
}
}) {
match self.token.kind {
token::CloseDelim(..) | token::Eof => break,
_ => {}
};
if let Some(ref t) = sep.sep {
if first {
first = false;
} else {
match self.expect(t) {
Ok(false) => {}
Ok(true) => {
recovered = true;
break;
}
Err(mut e) => {
// Attempt to keep parsing if it was a similar separator
if let Some(ref tokens) = t.similar_tokens() {
if tokens.contains(&self.token.kind) {
self.bump();
}
}
e.emit();
// Attempt to keep parsing if it was an omitted separator
match f(self) {
Ok(t) => {
v.push(t);
continue;
},
Err(mut e) => {
e.cancel();
break;
}
}
}
}
}
}
if sep.trailing_sep_allowed && kets.iter().any(|k| {
match expect {
TokenExpectType::Expect => self.check(k),
TokenExpectType::NoExpect => self.token == **k,
}
}) {
break;
}
let t = f(self)?;
v.push(t);
}
Ok((v, recovered))
}
/// Parses a sequence, including the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_unspanned_seq<T, F>(
&mut self,
bra: &TokenKind,
ket: &TokenKind,
sep: SeqSep,
f: F,
) -> PResult<'a, Vec<T>> where
F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
{
self.expect(bra)?;
let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
if !recovered {
self.eat(ket);
}
Ok(result)
}
/// Advance the parser by one token
pub fn bump(&mut self) {
if self.prev_token_kind == PrevTokenKind::Eof {
// Bumping after EOF is a bad sign, usually an infinite loop.
self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
}
self.prev_span = self.meta_var_span.take().unwrap_or(self.token.span);
// Record last token kind for possible error recovery.
self.prev_token_kind = match self.token.kind {
token::DocComment(..) => PrevTokenKind::DocComment,
token::Comma => PrevTokenKind::Comma,
token::BinOp(token::Plus) => PrevTokenKind::Plus,
token::BinOp(token::Or) => PrevTokenKind::BitOr,
token::Interpolated(..) => PrevTokenKind::Interpolated,
token::Eof => PrevTokenKind::Eof,
token::Ident(..) => PrevTokenKind::Ident,
_ => PrevTokenKind::Other,
};
self.token = self.next_tok();
self.expected_tokens.clear();
// check after each token
self.process_potential_macro_variable();
}
/// Advance the parser using provided token as a next one. Use this when
/// consuming a part of a token. For example a single `<` from `<<`.
fn bump_with(&mut self, next: TokenKind, span: Span) {
self.prev_span = self.token.span.with_hi(span.lo());
// It would be incorrect to record the kind of the current token, but
// fortunately for tokens currently using `bump_with`, the
// prev_token_kind will be of no use anyway.
self.prev_token_kind = PrevTokenKind::Other;
self.token = Token::new(next, span);
self.expected_tokens.clear();
}
pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
F: FnOnce(&Token) -> R,
{
if dist == 0 {
return f(&self.token);
}
let frame = &self.token_cursor.frame;
f(&match frame.tree_cursor.look_ahead(dist - 1) {
Some(tree) => match tree {
TokenTree::Token(token) => token,
TokenTree::Delimited(dspan, delim, _) =>
Token::new(token::OpenDelim(delim), dspan.open),
}
None => Token::new(token::CloseDelim(frame.delim), frame.span.close)
})
}
/// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
}
/// Is the current token one of the keywords that signals a bare function type?
fn token_is_bare_fn_keyword(&mut self) -> bool {
self.check_keyword(kw::Fn) ||
self.check_keyword(kw::Unsafe) ||
self.check_keyword(kw::Extern)
}
/// Parses a `TyKind::BareFn` type.
fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
/*
[unsafe] [extern "ABI"] fn (S) -> T
^~~~^ ^~~~^ ^~^ ^
| | | |
| | | Return type
| | Argument types
| |
| ABI
Function Style
*/
let unsafety = self.parse_unsafety();
let abi = if self.eat_keyword(kw::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(kw::Fn)?;
let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
let ret_ty = self.parse_ret_ty(false)?;
let decl = P(FnDecl {
inputs,
output: ret_ty,
c_variadic,
});
Ok(TyKind::BareFn(P(BareFnTy {
abi,
unsafety,
generic_params,
decl,
})))
}
/// Parses asyncness: `async` or nothing.
fn parse_asyncness(&mut self) -> IsAsync {
if self.eat_keyword(kw::Async) {
IsAsync::Async {
closure_id: ast::DUMMY_NODE_ID,
return_impl_trait_id: ast::DUMMY_NODE_ID,
}
} else {
IsAsync::NotAsync
}
}
/// Parses unsafety: `unsafe` or nothing.
fn parse_unsafety(&mut self) -> Unsafety {
if self.eat_keyword(kw::Unsafe) {
Unsafety::Unsafe
} else {
Unsafety::Normal
}
}
/// Parses the items in a trait declaration.
pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
maybe_whole!(self, NtTraitItem, |x| x);
let attrs = self.parse_outer_attributes()?;
let mut unclosed_delims = vec![];
let (mut item, tokens) = self.collect_tokens(|this| {
let item = this.parse_trait_item_(at_end, attrs);
unclosed_delims.append(&mut this.unclosed_delims);
item
})?;
self.unclosed_delims.append(&mut unclosed_delims);
// See `parse_item` for why this clause is here.
if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
item.tokens = Some(tokens);
}
Ok(item)
}
fn parse_trait_item_(&mut self,
at_end: &mut bool,
mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
let lo = self.token.span;
self.eat_bad_pub();
let (name, node, generics) = if self.eat_keyword(kw::Type) {
self.parse_trait_item_assoc_ty()?
} else if self.is_const_item() {
self.expect_keyword(kw::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
let default = if self.eat(&token::Eq) {
let expr = self.parse_expr()?;
self.expect(&token::Semi)?;
Some(expr)
} else {
self.expect(&token::Semi)?;
None
};
(ident, TraitItemKind::Const(ty, default), ast::Generics::default())
} else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
// trait item macro.
(Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
} else {
let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
let ident = self.parse_ident()?;
let mut generics = self.parse_generics()?;
let decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
// This is somewhat dubious; We don't want to allow
// argument names to be left off if there is a
// definition...
// We don't allow argument names to be left off in edition 2018.
let is_name_required = p.token.span.rust_2018();
p.parse_arg_general(true, false, |_| is_name_required)
})?;
generics.where_clause = self.parse_where_clause()?;
let sig = ast::MethodSig {
header: FnHeader {
unsafety,
constness,
abi,
asyncness,
},
decl,
};
let body = match self.token.kind {
token::Semi => {
self.bump();
*at_end = true;
debug!("parse_trait_methods(): parsing required method");
None
}
token::OpenDelim(token::Brace) => {
debug!("parse_trait_methods(): parsing provided method");
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
token::Interpolated(ref nt) => {
match **nt {
token::NtBlock(..) => {
*at_end = true;
let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(inner_attrs.iter().cloned());
Some(body)
}
_ => {
return self.expected_semi_or_open_brace();
}
}
}
_ => {
return self.expected_semi_or_open_brace();
}
};
(ident, ast::TraitItemKind::Method(sig, body), generics)
};
Ok(TraitItem {
id: ast::DUMMY_NODE_ID,
ident: name,
attrs,
generics,
node,
span: lo.to(self.prev_span),
tokens: None,
})
}
/// Parses an optional return type `[ -> TY ]` in a function declaration.
fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
if self.eat(&token::RArrow) {
Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
} else {
Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
}
}
/// Parses a type.
pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(true, true, false)
}
/// Parses a type in restricted contexts where `+` is not permitted.
///
/// Example 1: `&'a TYPE`
/// `+` is prohibited to maintain operator priority (P(+) < P(&)).
/// Example 2: `value1 as TYPE + value2`
/// `+` is prohibited to avoid interactions with expression grammar.
fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(false, true, false)
}
fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
maybe_whole!(self, NtTy, |x| x);
let lo = self.token.span;
let mut impl_dyn_multi = false;
let node = if self.eat(&token::OpenDelim(token::Paren)) {
// `(TYPE)` is a parenthesized type.
// `(TYPE,)` is a tuple with a single field of type TYPE.
let mut ts = vec![];
let mut last_comma = false;
while self.token != token::CloseDelim(token::Paren) {
ts.push(self.parse_ty()?);
if self.eat(&token::Comma) {
last_comma = true;
} else {
last_comma = false;
break;
}
}
let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
self.expect(&token::CloseDelim(token::Paren))?;
if ts.len() == 1 && !last_comma {
let ty = ts.into_iter().nth(0).unwrap().into_inner();
let maybe_bounds = allow_plus && self.token.is_like_plus();
match ty.node {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
}
TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
let path = match bounds[0] {
GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
};
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
TyKind::Tup(ts)
}
} else if self.eat(&token::Not) {
// Never type `!`
TyKind::Never
} else if self.eat(&token::BinOp(token::Star)) {
// Raw pointer
TyKind::Ptr(self.parse_ptr()?)
} else if self.eat(&token::OpenDelim(token::Bracket)) {
// Array or slice
let t = self.parse_ty()?;
// Parse optional `; EXPR` in `[TYPE; EXPR]`
let t = match self.maybe_parse_fixed_length_of_vec()? {
None => TyKind::Slice(t),
Some(length) => TyKind::Array(t, AnonConst {
id: ast::DUMMY_NODE_ID,
value: length,
}),
};
self.expect(&token::CloseDelim(token::Bracket))?;
t
} else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
// Reference
self.expect_and()?;
self.parse_borrowed_pointee()?
} else if self.eat_keyword_noexpect(kw::Typeof) {
// `typeof(EXPR)`
// In order to not be ambiguous, the type must be surrounded by parens.
self.expect(&token::OpenDelim(token::Paren))?;
let e = AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
};
self.expect(&token::CloseDelim(token::Paren))?;
TyKind::Typeof(e)
} else if self.eat_keyword(kw::Underscore) {
// A type to be inferred `_`
TyKind::Infer
} else if self.token_is_bare_fn_keyword() {
// Function pointer type
self.parse_ty_bare_fn(Vec::new())?
} else if self.check_keyword(kw::For) {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let lo = self.token.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
if self.token_is_bare_fn_keyword() {
self.parse_ty_bare_fn(lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus && self.check_plus();
self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
}
} else if self.eat_keyword(kw::Impl) {
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
} else if self.check_keyword(kw::Dyn) &&
(self.token.span.rust_2018() ||
self.look_ahead(1, |t| t.can_begin_bound() &&
!can_continue_type_after_non_fn_ident(t))) {
self.bump(); // `dyn`
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
} else if self.check(&token::Question) ||
self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
// Bound list (trait object type)
TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
TraitObjectSyntax::None)
} else if self.eat_lt() {
// Qualified path
let (qself, path) = self.parse_qpath(PathStyle::Type)?;
TyKind::Path(Some(qself), path)
} else if self.token.is_path_start() {
// Simple path
let path = self.parse_path(PathStyle::Type)?;
if self.eat(&token::Not) {
// Macro invocation in type position
let (delim, tts) = self.expect_delimited_token_tree()?;
let node = Mac_ { path, tts, delim };
TyKind::Mac(respan(lo.to(self.prev_span), node))
} else {
// Just a type path or bound list (trait object type) starting with a trait.
// `Type`
// `Trait1 + Trait2 + 'a`
if allow_plus && self.check_plus() {
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
} else {
TyKind::Path(None, path)
}
}
} else if self.check(&token::DotDotDot) {
if allow_c_variadic {
self.eat(&token::DotDotDot);
TyKind::CVarArgs
} else {
return Err(self.fatal(
"only foreign functions are allowed to be C-variadic"
));
}
} else {
let msg = format!("expected type, found {}", self.this_token_descr());
return Err(self.fatal(&msg));
};
let span = lo.to(self.prev_span);
let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
// Try to recover from use of `+` with incorrect priority.
self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
}
fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
if parse_plus {
self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
}
Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
}
fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
let mutbl = self.parse_mutability();
let ty = self.parse_ty_no_plus()?;
return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
}
fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
let mutbl = if self.eat_keyword(kw::Mut) {
Mutability::Mutable
} else if self.eat_keyword(kw::Const) {
Mutability::Immutable
} else {
let span = self.prev_span;
let msg = "expected mut or const in raw pointer type";
self.struct_span_err(span, msg)
.span_label(span, msg)
.help("use `*mut T` or `*const T` as appropriate")
.emit();
Mutability::Immutable
};
let t = self.parse_ty_no_plus()?;
Ok(MutTy { ty: t, mutbl: mutbl })
}
fn is_named_argument(&self) -> bool {
let offset = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
_ => 0,
}
token::BinOp(token::And) | token::AndAnd => 1,
_ if self.token.is_keyword(kw::Mut) => 1,
_ => 0,
};
self.look_ahead(offset, |t| t.is_ident()) &&
self.look_ahead(offset + 1, |t| t == &token::Colon)
}
/// Skips unexpected attributes and doc comments in this position and emits an appropriate
/// error.
/// This version of parse arg doesn't necessarily require identifier names.
fn parse_arg_general<F>(
&mut self,
is_trait_item: bool,
allow_c_variadic: bool,
is_name_required: F,
) -> PResult<'a, Arg>
where
F: Fn(&token::Token) -> bool
{
let attrs = self.parse_arg_attributes()?;
if let Ok(Some(mut arg)) = self.parse_self_arg() {
arg.attrs = attrs.into();
return self.recover_bad_self_arg(arg, is_trait_item);
}
let is_name_required = is_name_required(&self.token);
let (pat, ty) = if is_name_required || self.is_named_argument() {
debug!("parse_arg_general parse_pat (is_name_required:{})", is_name_required);
let pat = self.parse_pat(Some("argument name"))?;
if let Err(mut err) = self.expect(&token::Colon) {
if let Some(ident) = self.argument_without_type(
&mut err,
pat,
is_name_required,
is_trait_item,
) {
err.emit();
return Ok(dummy_arg(ident));
} else {
return Err(err);
}
}
self.eat_incorrect_doc_comment_for_arg_type();
(pat, self.parse_ty_common(true, true, allow_c_variadic)?)
} else {
debug!("parse_arg_general ident_to_pat");
let parser_snapshot_before_ty = self.clone();
self.eat_incorrect_doc_comment_for_arg_type();
let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
if ty.is_ok() && self.token != token::Comma &&
self.token != token::CloseDelim(token::Paren) {
// This wasn't actually a type, but a pattern looking like a type,
// so we are going to rollback and re-parse for recovery.
ty = self.unexpected();
}
match ty {
Ok(ty) => {
let ident = Ident::new(kw::Invalid, self.prev_span);
let pat = P(Pat {
id: ast::DUMMY_NODE_ID,
node: PatKind::Ident(
BindingMode::ByValue(Mutability::Immutable), ident, None),
span: ty.span,
});
(pat, ty)
}
Err(mut err) => {
// If this is a C-variadic argument and we hit an error, return the
// error.
if self.token == token::DotDotDot {
return Err(err);
}
// Recover from attempting to parse the argument as a type without pattern.
err.cancel();
mem::replace(self, parser_snapshot_before_ty);
self.recover_arg_parse()?
}
}
};
Ok(Arg { attrs: attrs.into(), id: ast::DUMMY_NODE_ID, pat, ty })
}
/// Parses an argument in a lambda header (e.g., `|arg, arg|`).
fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
let attrs = self.parse_arg_attributes()?;
let pat = self.parse_pat(Some("argument name"))?;
let t = if self.eat(&token::Colon) {
self.parse_ty()?
} else {
P(Ty {
id: ast::DUMMY_NODE_ID,
node: TyKind::Infer,
span: self.prev_span,
})
};
Ok(Arg {
attrs: attrs.into(),
ty: t,
pat,
id: ast::DUMMY_NODE_ID
})
}
fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
if self.eat(&token::Semi) {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
/// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
maybe_whole_expr!(self);
let minus_lo = self.token.span;
let minus_present = self.eat(&token::BinOp(token::Minus));
let lo = self.token.span;
let literal = self.parse_lit()?;
let hi = self.prev_span;
let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
if minus_present {
let minus_hi = self.prev_span;
let unary = self.mk_unary(UnOp::Neg, expr);
Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
} else {
Ok(expr)
}
}
fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
match self.token.kind {
token::Ident(name, _) if name.is_path_segment_keyword() => {
let span = self.token.span;
self.bump();
Ok(Ident::new(name, span))
}
_ => self.parse_ident(),
}
}
fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
match self.token.kind {
token::Ident(name, false) if name == kw::Underscore => {
let span = self.token.span;
self.bump();
Ok(Ident::new(name, span))
}
_ => self.parse_ident(),
}
}
/// Parses a qualified path.
/// Assumes that the leading `<` has been parsed already.
///
/// `qualified_path = <type [as trait_ref]>::path`
///
/// # Examples
/// `<T>::default`
/// `<T as U>::a`
/// `<T as U>::F::a<S>` (without disambiguator)
/// `<T as U>::F::a::<S>` (with disambiguator)
fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
let lo = self.prev_span;
let ty = self.parse_ty()?;
// `path` will contain the prefix of the path up to the `>`,
// if any (e.g., `U` in the `<T as U>::*` examples
// above). `path_span` has the span of that path, or an empty
// span in the case of something like `<T>::Bar`.
let (mut path, path_span);
if self.eat_keyword(kw::As) {
let path_lo = self.token.span;
path = self.parse_path(PathStyle::Type)?;
path_span = path_lo.to(self.prev_span);
} else {
path_span = self.token.span.to(self.token.span);
path = ast::Path { segments: Vec::new(), span: path_span };
}
// See doc comment for `unmatched_angle_bracket_count`.
self.expect(&token::Gt)?;
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
self.expect(&token::ModSep)?;
let qself = QSelf { ty, path_span, position: path.segments.len() };
self.parse_path_segments(&mut path.segments, style)?;
Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
}
/// Parses simple paths.
///
/// `path = [::] segment+`
/// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
///
/// # Examples
/// `a::b::C<D>` (without disambiguator)
/// `a::b::C::<D>` (with disambiguator)
/// `Fn(Args)` (without disambiguator)
/// `Fn::(Args)` (with disambiguator)
pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
maybe_whole!(self, NtPath, |path| {
if style == PathStyle::Mod &&
path.segments.iter().any(|segment| segment.args.is_some()) {
self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
}
path
});
let lo = self.meta_var_span.unwrap_or(self.token.span);
let mut segments = Vec::new();
let mod_sep_ctxt = self.token.span.ctxt();
if self.eat(&token::ModSep) {
segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
}
self.parse_path_segments(&mut segments, style)?;
Ok(ast::Path { segments, span: lo.to(self.prev_span) })
}
/// Like `parse_path`, but also supports parsing `Word` meta items into paths for
/// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
/// attributes.
pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
let meta_ident = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtMeta(ref meta) => match meta.node {
ast::MetaItemKind::Word => Some(meta.path.clone()),
_ => None,
},
_ => None,
},
_ => None,
};
if let Some(path) = meta_ident {
self.bump();
return Ok(path);
}
self.parse_path(style)
}
crate fn parse_path_segments(&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle)
-> PResult<'a, ()> {
loop {
let segment = self.parse_path_segment(style)?;
if style == PathStyle::Expr {
// In order to check for trailing angle brackets, we must have finished
// recursing (`parse_path_segment` can indirectly call this function),
// that is, the next token must be the highlighted part of the below example:
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// As opposed to the below highlight (if we had only finished the first
// recursion):
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// `PathStyle::Expr` is only provided at the root invocation and never in
// `parse_path_segment` to recurse and therefore can be checked to maintain
// this invariant.
self.check_trailing_angle_brackets(&segment, token::ModSep);
}
segments.push(segment);
if self.is_import_coupler() || !self.eat(&token::ModSep) {
return Ok(());
}
}
}
fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
let ident = self.parse_path_segment_ident()?;
let is_args_start = |token: &Token| match token.kind {
token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
| token::LArrow => true,
_ => false,
};
let check_args_start = |this: &mut Self| {
this.expected_tokens.extend_from_slice(
&[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
);
is_args_start(&this.token)
};
Ok(if style == PathStyle::Type && check_args_start(self) ||
style != PathStyle::Mod && self.check(&token::ModSep)
&& self.look_ahead(1, |t| is_args_start(t)) {
// We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
// it isn't, then we reset the unmatched angle bracket count as we're about to start
// parsing a new path.
if style == PathStyle::Expr {
self.unmatched_angle_bracket_count = 0;
self.max_angle_bracket_count = 0;
}
// Generic arguments are found - `<`, `(`, `::<` or `::(`.
self.eat(&token::ModSep);
let lo = self.token.span;
let args = if self.eat_lt() {
// `<'a, T, A = U>`
let (args, constraints) =
self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
self.expect_gt()?;
let span = lo.to(self.prev_span);
AngleBracketedArgs { args, constraints, span }.into()
} else {
// `(T, U) -> R`
self.bump(); // `(`
let (inputs, recovered) = self.parse_seq_to_before_tokens(
&[&token::CloseDelim(token::Paren)],
SeqSep::trailing_allowed(token::Comma),
TokenExpectType::Expect,
|p| p.parse_ty())?;
if !recovered {
self.bump(); // `)`
}
let span = lo.to(self.prev_span);
let output = if self.eat(&token::RArrow) {
Some(self.parse_ty_common(false, false, false)?)
} else {
None
};
ParenthesizedArgs { inputs, output, span }.into()
};
PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
} else {
// Generic arguments are not found.
PathSegment::from_ident(ident)
})
}
crate fn check_lifetime(&mut self) -> bool {
self.expected_tokens.push(TokenType::Lifetime);
self.token.is_lifetime()
}
/// Parses a single lifetime `'a` or panics.
crate fn expect_lifetime(&mut self) -> Lifetime {
if let Some(ident) = self.token.lifetime() {
let span = self.token.span;
self.bump();
Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
} else {
self.span_bug(self.token.span, "not a lifetime")
}
}
fn eat_label(&mut self) -> Option<Label> {
if let Some(ident) = self.token.lifetime() {
let span = self.token.span;
self.bump();
Some(Label { ident: Ident::new(ident.name, span) })
} else {
None
}
}
/// Parses mutability (`mut` or nothing).
fn parse_mutability(&mut self) -> Mutability {
if self.eat_keyword(kw::Mut) {
Mutability::Mutable
} else {
Mutability::Immutable
}
}
fn parse_field_name(&mut self) -> PResult<'a, Ident> {
if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
self.token.kind {
self.expect_no_suffix(self.token.span, "a tuple index", suffix);
self.bump();
Ok(Ident::new(symbol, self.prev_span))
} else {
self.parse_ident_common(false)
}
}
/// Parse ident (COLON expr)?
fn parse_field(&mut self) -> PResult<'a, Field> {
let attrs = self.parse_outer_attributes()?;
let lo = self.token.span;
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
t == &token::Colon || t == &token::Eq
}) {
let fieldname = self.parse_field_name()?;
// Check for an equals token. This means the source incorrectly attempts to
// initialize a field with an eq rather than a colon.
if self.token == token::Eq {
self.diagnostic()
.struct_span_err(self.token.span, "expected `:`, found `=`")
.span_suggestion(
fieldname.span.shrink_to_hi().to(self.token.span),
"replace equals symbol with a colon",
":".to_string(),
Applicability::MachineApplicable,
)
.emit();
}
self.bump(); // `:`
(fieldname, self.parse_expr()?, false)
} else {
let fieldname = self.parse_ident_common(false)?;
// Mimic `x: x` for the `x` field shorthand.
let path = ast::Path::from_ident(fieldname);
let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
(fieldname, expr, true)
};
Ok(ast::Field {
ident: fieldname,
span: lo.to(expr.span),
expr,
is_shorthand,
attrs: attrs.into(),
})
}
crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
}
fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
ExprKind::Unary(unop, expr)
}
fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::Binary(binop, lhs, rhs)
}
fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
ExprKind::Call(f, args)
}
fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
ExprKind::Index(expr, idx)
}
fn mk_range(&self,
start: Option<P<Expr>>,
end: Option<P<Expr>>,
limits: RangeLimits)
-> PResult<'a, ast::ExprKind> {
if end.is_none() && limits == RangeLimits::Closed {
Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd))
} else {
Ok(ExprKind::Range(start, end, limits))
}
}
fn mk_assign_op(&self, binop: ast::BinOp,
lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
ExprKind::AssignOp(binop, lhs, rhs)
}
fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
let delim = match self.token.kind {
token::OpenDelim(delim) => delim,
_ => {
let msg = "expected open delimiter";
let mut err = self.fatal(msg);
err.span_label(self.token.span, msg);
return Err(err)
}
};
let tts = match self.parse_token_tree() {
TokenTree::Delimited(_, _, tts) => tts,
_ => unreachable!(),
};
let delim = match delim {
token::Paren => MacDelimiter::Parenthesis,
token::Bracket => MacDelimiter::Bracket,
token::Brace => MacDelimiter::Brace,
token::NoDelim => self.bug("unexpected no delimiter"),
};
Ok((delim, tts.into()))
}
/// At the bottom (top?) of the precedence hierarchy,
/// Parses things like parenthesized exprs, macros, `return`, etc.
///
/// N.B., this does not parse outer attributes, and is private because it only works
/// correctly if called from `parse_dot_or_call_expr()`.
fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
maybe_recover_from_interpolated_ty_qpath!(self, true);
maybe_whole_expr!(self);
// Outer attributes are already parsed and will be
// added to the return value after the fact.
//
// Therefore, prevent sub-parser from parsing
// attributes by giving them a empty "already parsed" list.
let mut attrs = ThinVec::new();
let lo = self.token.span;
let mut hi = self.token.span;
let ex: ExprKind;
macro_rules! parse_lit {
() => {
match self.parse_lit() {
Ok(literal) => {
hi = self.prev_span;
ex = ExprKind::Lit(literal);
}
Err(mut err) => {
self.cancel(&mut err);
return Err(self.expected_expression_found());
}
}
}
}
// Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
match self.token.kind {
// This match arm is a special-case of the `_` match arm below and
// could be removed without changing functionality, but it's faster
// to have it here, especially for programs with large constants.
token::Literal(_) => {
parse_lit!()
}
token::OpenDelim(token::Paren) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
// (e) is parenthesized e
// (e,) is a tuple with only one field, e
let mut es = vec![];
let mut trailing_comma = false;
let mut recovered = false;
while self.token != token::CloseDelim(token::Paren) {
es.push(match self.parse_expr() {
Ok(es) => es,
Err(err) => {
// recover from parse error in tuple list
return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
}
});
recovered = self.expect_one_of(
&[],
&[token::Comma, token::CloseDelim(token::Paren)],
)?;
if self.eat(&token::Comma) {
trailing_comma = true;
} else {
trailing_comma = false;
break;
}
}
if !recovered {
self.bump();
}
hi = self.prev_span;
ex = if es.len() == 1 && !trailing_comma {
ExprKind::Paren(es.into_iter().nth(0).unwrap())
} else {
ExprKind::Tup(es)
};
}
token::OpenDelim(token::Brace) => {
return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
}
token::BinOp(token::Or) | token::OrOr => {
return self.parse_lambda_expr(attrs);
}
token::OpenDelim(token::Bracket) => {
self.bump();
attrs.extend(self.parse_inner_attributes()?);
if self.eat(&token::CloseDelim(token::Bracket)) {
// Empty vector.
ex = ExprKind::Array(Vec::new());
} else {
// Nonempty vector.
let first_expr = self.parse_expr()?;
if self.eat(&token::Semi) {
// Repeating array syntax: [ 0; 512 ]
let count = AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
};
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Repeat(first_expr, count);
} else if self.eat(&token::Comma) {
// Vector with two or more elements.
let remaining_exprs = self.parse_seq_to_end(
&token::CloseDelim(token::Bracket),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
let mut exprs = vec![first_expr];
exprs.extend(remaining_exprs);
ex = ExprKind::Array(exprs);
} else {
// Vector with one element.
self.expect(&token::CloseDelim(token::Bracket))?;
ex = ExprKind::Array(vec![first_expr]);
}
}
hi = self.prev_span;
}
_ => {
if self.eat_lt() {
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
hi = path.span;
return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
}
if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
return self.parse_lambda_expr(attrs);
}
if self.eat_keyword(kw::If) {
return self.parse_if_expr(attrs);
}
if self.eat_keyword(kw::For) {
let lo = self.prev_span;
return self.parse_for_expr(None, lo, attrs);
}
if self.eat_keyword(kw::While) {
let lo = self.prev_span;
return self.parse_while_expr(None, lo, attrs);
}
if let Some(label) = self.eat_label() {
let lo = label.ident.span;
self.expect(&token::Colon)?;
if self.eat_keyword(kw::While) {
return self.parse_while_expr(Some(label), lo, attrs)
}
if self.eat_keyword(kw::For) {
return self.parse_for_expr(Some(label), lo, attrs)
}
if self.eat_keyword(kw::Loop) {
return self.parse_loop_expr(Some(label), lo, attrs)
}
if self.token == token::OpenDelim(token::Brace) {
return self.parse_block_expr(Some(label),
lo,
BlockCheckMode::Default,
attrs);
}
let msg = "expected `while`, `for`, `loop` or `{` after a label";
let mut err = self.fatal(msg);
err.span_label(self.token.span, msg);
return Err(err);
}
if self.eat_keyword(kw::Loop) {
let lo = self.prev_span;
return self.parse_loop_expr(None, lo, attrs);
}
if self.eat_keyword(kw::Continue) {
let label = self.eat_label();
let ex = ExprKind::Continue(label);
let hi = self.prev_span;
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
if self.eat_keyword(kw::Match) {
let match_sp = self.prev_span;
return self.parse_match_expr(attrs).map_err(|mut err| {
err.span_label(match_sp, "while parsing this match expression");
err
});
}
if self.eat_keyword(kw::Unsafe) {
return self.parse_block_expr(
None,
lo,
BlockCheckMode::Unsafe(ast::UserProvided),
attrs);
}
if self.is_do_catch_block() {
let mut db = self.fatal("found removed `do catch` syntax");
db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
return Err(db);
}
if self.is_try_block() {
let lo = self.token.span;
assert!(self.eat_keyword(kw::Try));
return self.parse_try_block(lo, attrs);
}
// Span::rust_2018() is somewhat expensive; don't get it repeatedly.
let is_span_rust_2018 = self.token.span.rust_2018();
if is_span_rust_2018 && self.check_keyword(kw::Async) {
return if self.is_async_block() { // check for `async {` and `async move {`
self.parse_async_block(attrs)
} else {
self.parse_lambda_expr(attrs)
};
}
if self.eat_keyword(kw::Return) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Ret(Some(e));
} else {
ex = ExprKind::Ret(None);
}
} else if self.eat_keyword(kw::Break) {
let label = self.eat_label();
let e = if self.token.can_begin_expr()
&& !(self.token == token::OpenDelim(token::Brace)
&& self.restrictions.contains(
Restrictions::NO_STRUCT_LITERAL)) {
Some(self.parse_expr()?)
} else {
None
};
ex = ExprKind::Break(label, e);
hi = self.prev_span;
} else if self.eat_keyword(kw::Yield) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
hi = e.span;
ex = ExprKind::Yield(Some(e));
} else {
ex = ExprKind::Yield(None);
}
} else if self.token.is_keyword(kw::Let) {
// Catch this syntax error here, instead of in `parse_ident`, so
// that we can explicitly mention that let is not to be used as an expression
let mut db = self.fatal("expected expression, found statement (`let`)");
db.span_label(self.token.span, "expected expression");
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
hi = await_hi;
ex = e_kind;
} else if self.token.is_path_start() {
let path = self.parse_path(PathStyle::Expr)?;
// `!`, as an operator, is prefix, so we know this isn't that
if self.eat(&token::Not) {
// MACRO INVOCATION expression
let (delim, tts) = self.expect_delimited_token_tree()?;
hi = self.prev_span;
ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
} else if self.check(&token::OpenDelim(token::Brace)) {
if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
return expr;
} else {
hi = path.span;
ex = ExprKind::Path(None, path);
}
} else {
hi = path.span;
ex = ExprKind::Path(None, path);
}
} else {
if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
// Don't complain about bare semicolons after unclosed braces
// recovery in order to keep the error count down. Fixing the
// delimiters will possibly also fix the bare semicolon found in
// expression context. For example, silence the following error:
// ```
// error: expected expression, found `;`
// --> file.rs:2:13
// |
// 2 | foo(bar(;
// | ^ expected expression
// ```
self.bump();
return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
}
parse_lit!()
}
}
}
let expr = self.mk_expr(lo.to(hi), ex, attrs);
self.maybe_recover_from_bad_qpath(expr, true)
}
/// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
/// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
/// `await { <expr> }`.
fn parse_await_macro_or_alt(
&mut self,
lo: Span,
await_sp: Span,
) -> PResult<'a, (Span, ExprKind)> {
if self.token == token::Not {
// Handle correct `await!(<expr>)`.
// FIXME: make this an error when `await!` is no longer supported
// https://github.com/rust-lang/rust/issues/60610
self.expect(&token::Not)?;
self.expect(&token::OpenDelim(token::Paren))?;
let expr = self.parse_expr().map_err(|mut err| {
err.span_label(await_sp, "while parsing this await macro call");
err
})?;
self.expect(&token::CloseDelim(token::Paren))?;
Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
} else { // Handle `await <expr>`.
self.parse_incorrect_await_syntax(lo, await_sp)
}
}
fn maybe_parse_struct_expr(
&mut self,
lo: Span,
path: &ast::Path,
attrs: &ThinVec<Attribute>,
) -> Option<PResult<'a, P<Expr>>> {
let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
// `{ ident, ` cannot start a block
self.look_ahead(2, |t| t == &token::Comma) ||
self.look_ahead(2, |t| t == &token::Colon) && (
// `{ ident: token, ` cannot start a block
self.look_ahead(4, |t| t == &token::Comma) ||
// `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
self.look_ahead(3, |t| !t.can_begin_type())
)
);
if struct_allowed || certainly_not_a_block() {
// This is a struct literal, but we don't can't accept them here
let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
if let (Ok(expr), false) = (&expr, struct_allowed) {
let mut err = self.diagnostic().struct_span_err(
expr.span,
"struct literals are not allowed here",
);
err.multipart_suggestion(
"surround the struct literal with parentheses",
vec![
(lo.shrink_to_lo(), "(".to_string()),
(expr.span.shrink_to_hi(), ")".to_string()),
],
Applicability::MachineApplicable,
);
err.emit();
}
return Some(expr);
}
None
}
fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let struct_sp = lo.to(self.prev_span);
self.bump();
let mut fields = Vec::new();
let mut base = None;
attrs.extend(self.parse_inner_attributes()?);
while self.token != token::CloseDelim(token::Brace) {
if self.eat(&token::DotDot) {
let exp_span = self.prev_span;
match self.parse_expr() {
Ok(e) => {
base = Some(e);
}
Err(mut e) => {
e.emit();
self.recover_stmt();
}
}
if self.token == token::Comma {
let mut err = self.sess.span_diagnostic.mut_span_err(
exp_span.to(self.prev_span),
"cannot use a comma after the base struct",
);
err.span_suggestion_short(
self.token.span,
"remove this comma",
String::new(),
Applicability::MachineApplicable
);
err.note("the base struct must always be the last field");
err.emit();
self.recover_stmt();
}
break;
}
let mut recovery_field = None;
if let token::Ident(name, _) = self.token.kind {
if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
// Use in case of error after field-looking code: `S { foo: () with a }`
recovery_field = Some(ast::Field {
ident: Ident::new(name, self.token.span),
span: self.token.span,
expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()),
is_shorthand: false,
attrs: ThinVec::new(),
});
}
}
let mut parsed_field = None;
match self.parse_field() {
Ok(f) => parsed_field = Some(f),
Err(mut e) => {
e.span_label(struct_sp, "while parsing this struct");
e.emit();
// If the next token is a comma, then try to parse
// what comes next as additional fields, rather than
// bailing out until next `}`.
if self.token != token::Comma {
self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
if self.token != token::Comma {
break;
}
}
}
}
match self.expect_one_of(&[token::Comma],
&[token::CloseDelim(token::Brace)]) {
Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
// only include the field if there's no parse error for the field name
fields.push(f);
}
Err(mut e) => {
if let Some(f) = recovery_field {
fields.push(f);
}
e.span_label(struct_sp, "while parsing this struct");
e.emit();
self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
self.eat(&token::Comma);
}
}
}
let span = lo.to(self.token.span);
self.expect(&token::CloseDelim(token::Brace))?;
return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
}
fn parse_or_use_outer_attributes(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, ThinVec<Attribute>> {
if let Some(attrs) = already_parsed_attrs {
Ok(attrs)
} else {
self.parse_outer_attributes().map(|a| a.into())
}
}
/// Parses a block or unsafe block.
crate fn parse_block_expr(
&mut self,
opt_label: Option<Label>,
lo: Span,
blk_mode: BlockCheckMode,
outer_attrs: ThinVec<Attribute>,
) -> PResult<'a, P<Expr>> {
self.expect(&token::OpenDelim(token::Brace))?;
let mut attrs = outer_attrs;
attrs.extend(self.parse_inner_attributes()?);
let blk = self.parse_block_tail(lo, blk_mode)?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
}
/// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
fn parse_dot_or_call_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let b = self.parse_bottom_expr();
let (span, b) = self.interpolated_or_expr_span(b)?;
self.parse_dot_or_call_expr_with(b, span, attrs)
}
fn parse_dot_or_call_expr_with(&mut self,
e0: P<Expr>,
lo: Span,
mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
// Stitch the list of outer attributes onto the return value.
// A little bit ugly, but the best way given the current code
// structure
self.parse_dot_or_call_expr_with_(e0, lo)
.map(|expr|
expr.map(|mut expr| {
attrs.extend::<Vec<_>>(expr.attrs.into());
expr.attrs = attrs;
match expr.node {
ExprKind::If(..) | ExprKind::IfLet(..) => {
if !expr.attrs.is_empty() {
// Just point to the first attribute in there...
let span = expr.attrs[0].span;
self.span_err(span,
"attributes are not yet allowed on `if` \
expressions");
}
}
_ => {}
}
expr
})
)
}
// Assuming we have just parsed `.`, continue parsing into an expression.
fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
let span = lo.to(self.prev_span);
let await_expr = self.mk_expr(
span,
ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
ThinVec::new(),
);
self.recover_from_await_method_call();
return Ok(await_expr);
}
let segment = self.parse_path_segment(PathStyle::Expr)?;
self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
Ok(match self.token.kind {
token::OpenDelim(token::Paren) => {
// Method call `expr.f()`
let mut args = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
)?;
args.insert(0, self_arg);
let span = lo.to(self.prev_span);
self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
}
_ => {
// Field access `expr.f`
if let Some(args) = segment.args {
self.span_err(args.span(),
"field expressions may not have generic arguments");
}
let span = lo.to(self.prev_span);
self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
}
})
}
fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
let mut e = e0;
let mut hi;
loop {
// expr?
while self.eat(&token::Question) {
let hi = self.prev_span;
e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
}
// expr.f
if self.eat(&token::Dot) {
match self.token.kind {
token::Ident(..) => {
e = self.parse_dot_suffix(e, lo)?;
}
token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
let span = self.token.span;
self.bump();
let field = ExprKind::Field(e, Ident::new(symbol, span));
e = self.mk_expr(lo.to(span), field, ThinVec::new());
self.expect_no_suffix(span, "a tuple index", suffix);
}
token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
self.bump();
let fstr = symbol.as_str();
let msg = format!("unexpected token: `{}`", symbol);
let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
err.span_label(self.prev_span, "unexpected token");
if fstr.chars().all(|x| "0123456789.".contains(x)) {
let float = match fstr.parse::<f64>().ok() {
Some(f) => f,
None => continue,
};
let sugg = pprust::to_string(|s| {
use crate::print::pprust::PrintState;
s.popen()?;
s.print_expr(&e)?;
s.s.word( ".")?;
s.print_usize(float.trunc() as usize)?;
s.pclose()?;
s.s.word(".")?;
s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
});
err.span_suggestion(
lo.to(self.prev_span),
"try parenthesizing the first index",
sugg,
Applicability::MachineApplicable
);
}
return Err(err);
}
_ => {
// FIXME Could factor this out into non_fatal_unexpected or something.
let actual = self.this_token_to_string();
self.span_err(self.token.span, &format!("unexpected token: `{}`", actual));
}
}
continue;
}
if self.expr_is_complete(&e) { break; }
match self.token.kind {
// expr(...)
token::OpenDelim(token::Paren) => {
let seq = self.parse_unspanned_seq(
&token::OpenDelim(token::Paren),
&token::CloseDelim(token::Paren),
SeqSep::trailing_allowed(token::Comma),
|p| Ok(p.parse_expr()?)
).map(|es| {
let nd = self.mk_call(e, es);
let hi = self.prev_span;
self.mk_expr(lo.to(hi), nd, ThinVec::new())
});
e = self.recover_seq_parse_error(token::Paren, lo, seq);
}
// expr[...]
// Could be either an index expression or a slicing expression.
token::OpenDelim(token::Bracket) => {
self.bump();
let ix = self.parse_expr()?;
hi = self.token.span;
self.expect(&token::CloseDelim(token::Bracket))?;
let index = self.mk_index(e, ix);
e = self.mk_expr(lo.to(hi), index, ThinVec::new())
}
_ => return Ok(e)
}
}
return Ok(e);
}
crate fn process_potential_macro_variable(&mut self) {
self.token = match self.token.kind {
token::Dollar if self.token.span.ctxt() != SyntaxContext::empty() &&
self.look_ahead(1, |t| t.is_ident()) => {
self.bump();
let name = match self.token.kind {
token::Ident(name, _) => name,
_ => unreachable!()
};
let span = self.prev_span.to(self.token.span);
self.diagnostic()
.struct_span_fatal(span, &format!("unknown macro variable `{}`", name))
.span_label(span, "unknown macro variable")
.emit();
self.bump();
return
}
token::Interpolated(ref nt) => {
self.meta_var_span = Some(self.token.span);
// Interpolated identifier and lifetime tokens are replaced with usual identifier
// and lifetime tokens, so the former are never encountered during normal parsing.
match **nt {
token::NtIdent(ident, is_raw) =>
Token::new(token::Ident(ident.name, is_raw), ident.span),
token::NtLifetime(ident) =>
Token::new(token::Lifetime(ident.name), ident.span),
_ => return,
}
}
_ => return,
};
}
/// Parses a single token tree from the input.
crate fn parse_token_tree(&mut self) -> TokenTree {
match self.token.kind {
token::OpenDelim(..) => {
let frame = mem::replace(&mut self.token_cursor.frame,
self.token_cursor.stack.pop().unwrap());
self.token.span = frame.span.entire();
self.bump();
TokenTree::Delimited(
frame.span,
frame.delim,
frame.tree_cursor.stream.into(),
)
},
token::CloseDelim(_) | token::Eof => unreachable!(),
_ => {
let token = self.token.take();
self.bump();
TokenTree::Token(token)
}
}
}
/// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
let mut tts = Vec::new();
while self.token != token::Eof {
tts.push(self.parse_token_tree());
}
Ok(tts)
}
pub fn parse_tokens(&mut self) -> TokenStream {
let mut result = Vec::new();
loop {
match self.token.kind {
token::Eof | token::CloseDelim(..) => break,
_ => result.push(self.parse_token_tree().into()),
}
}
TokenStream::new(result)
}
/// Parse a prefix-unary-operator expr
fn parse_prefix_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.token.span;
// Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
let (hi, ex) = match self.token.kind {
token::Not => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
// Suggest `!` for bitwise negation when encountering a `~`
token::Tilde => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
let span_of_tilde = lo;
let mut err = self.diagnostic()
.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
err.span_suggestion_short(
span_of_tilde,
"use `!` to perform bitwise negation",
"!".to_owned(),
Applicability::MachineApplicable
);
err.emit();
(lo.to(span), self.mk_unary(UnOp::Not, e))
}
token::BinOp(token::Minus) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Neg, e))
}
token::BinOp(token::Star) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Deref, e))
}
token::BinOp(token::And) | token::AndAnd => {
self.expect_and()?;
let m = self.parse_mutability();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::AddrOf(m, e))
}
token::Ident(..) if self.token.is_keyword(kw::Box) => {
self.bump();
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), ExprKind::Box(e))
}
token::Ident(..) if self.token.is_ident_named(sym::not) => {
// `not` is just an ordinary identifier in Rust-the-language,
// but as `rustc`-the-compiler, we can issue clever diagnostics
// for confused users who really want to say `!`
let token_cannot_continue_expr = |t: &Token| match t.kind {
// These tokens can start an expression after `!`, but
// can't continue an expression after an ident
token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
token::Literal(..) | token::Pound => true,
token::Interpolated(ref nt) => match **nt {
token::NtIdent(..) | token::NtExpr(..) |
token::NtBlock(..) | token::NtPath(..) => true,
_ => false,
},
_ => false
};
let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
if cannot_continue_expr {
self.bump();
// Emit the error ...
let mut err = self.diagnostic()
.struct_span_err(self.token.span,
&format!("unexpected {} after identifier",
self.this_token_descr()));
// span the `not` plus trailing whitespace to avoid
// trailing whitespace after the `!` in our suggestion
let to_replace = self.sess.source_map()
.span_until_non_whitespace(lo.to(self.token.span));
err.span_suggestion_short(
to_replace,
"use `!` to perform logical negation",
"!".to_owned(),
Applicability::MachineApplicable
);
err.emit();
// —and recover! (just as if we were in the block
// for the `token::Not` arm)
let e = self.parse_prefix_expr(None);
let (span, e) = self.interpolated_or_expr_span(e)?;
(lo.to(span), self.mk_unary(UnOp::Not, e))
} else {
return self.parse_dot_or_call_expr(Some(attrs));
}
}
_ => { return self.parse_dot_or_call_expr(Some(attrs)); }
};
return Ok(self.mk_expr(lo.to(hi), ex, attrs));
}
/// Parses an associative expression.
///
/// This parses an expression accounting for associativity and precedence of the operators in
/// the expression.
#[inline]
fn parse_assoc_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
self.parse_assoc_expr_with(0, already_parsed_attrs.into())
}
/// Parses an associative expression with operators of at least `min_prec` precedence.
fn parse_assoc_expr_with(&mut self,
min_prec: usize,
lhs: LhsExpr)
-> PResult<'a, P<Expr>> {
let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
expr
} else {
let attrs = match lhs {
LhsExpr::AttributesParsed(attrs) => Some(attrs),
_ => None,
};
if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
return self.parse_prefix_range_expr(attrs);
} else {
self.parse_prefix_expr(attrs)?
}
};
match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
(true, None) => {
// Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
return Ok(lhs);
}
(false, _) => {} // continue parsing the expression
// An exhaustive check is done in the following block, but these are checked first
// because they *are* ambiguous but also reasonable looking incorrect syntax, so we
// want to keep their span info to improve diagnostics in these cases in a later stage.
(true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
(true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
(true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
(true, Some(AssocOp::Add)) // `{ 42 } + 42
// If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
// `if x { a } else { b } && if y { c } else { d }`
if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
// These cases are ambiguous and can't be identified in the parser alone
let sp = self.sess.source_map().start_point(self.token.span);
self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
return Ok(lhs);
}
(true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
return Ok(lhs);
}
(true, Some(_)) => {
// We've found an expression that would be parsed as a statement, but the next
// token implies this should be parsed as an expression.
// For example: `if let Some(x) = x { x } else { 0 } / 2`
let mut err = self.sess.span_diagnostic.struct_span_err(self.token.span, &format!(
"expected expression, found `{}`",
pprust::token_to_string(&self.token),
));
err.span_label(self.token.span, "expected expression");
self.sess.expr_parentheses_needed(
&mut err,
lhs.span,
Some(pprust::expr_to_string(&lhs),
));
err.emit();
}
}
self.expected_tokens.push(TokenType::Operator);
while let Some(op) = AssocOp::from_token(&self.token) {
// Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
// it refers to. Interpolated identifiers are unwrapped early and never show up here
// as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
// it as "interpolated", it doesn't change the answer for non-interpolated idents.
let lhs_span = match (self.prev_token_kind, &lhs.node) {
(PrevTokenKind::Interpolated, _) => self.prev_span,
(PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
if path.segments.len() == 1 => self.prev_span,
_ => lhs.span,
};
let cur_op_span = self.token.span;
let restrictions = if op.is_assign_like() {
self.restrictions & Restrictions::NO_STRUCT_LITERAL
} else {
self.restrictions
};
let prec = op.precedence();
if prec < min_prec {
break;
}
// Check for deprecated `...` syntax
if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
self.err_dotdotdot_syntax(self.token.span);
}
self.bump();
if op.is_comparison() {
self.check_no_chained_comparison(&lhs, &op);
}
// Special cases:
if op == AssocOp::As {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
continue
} else if op == AssocOp::Colon {
let maybe_path = self.could_ascription_be_path(&lhs.node);
let next_sp = self.token.span;
lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
Ok(lhs) => lhs,
Err(mut err) => {
self.bad_type_ascription(
&mut err,
lhs_span,
cur_op_span,
next_sp,
maybe_path,
);
return Err(err);
}
};
continue
} else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
// If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
// generalise it to the Fixity::None code.
//
// We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
// two variants are handled with `parse_prefix_range_expr` call above.
let rhs = if self.is_at_start_of_range_notation_rhs() {
Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
} else {
None
};
let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
x.span
} else {
cur_op_span
});
let limits = if op == AssocOp::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = self.mk_range(Some(lhs), rhs, limits)?;
lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
break
}
let fixity = op.fixity();
let prec_adjustment = match fixity {
Fixity::Right => 0,
Fixity::Left => 1,
// We currently have no non-associative operators that are not handled above by
// the special cases. The code is here only for future convenience.
Fixity::None => 1,
};
let rhs = self.with_res(
restrictions - Restrictions::STMT_EXPR,
|this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
)?;
// Make sure that the span of the parent node is larger than the span of lhs and rhs,
// including the attributes.
let lhs_span = lhs
.attrs
.iter()
.filter(|a| a.style == AttrStyle::Outer)
.next()
.map_or(lhs_span, |a| a.span);
let span = lhs_span.to(rhs.span);
lhs = match op {
AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
AssocOp::Greater | AssocOp::GreaterEqual => {
let ast_op = op.to_ast_binop().unwrap();
let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
self.mk_expr(span, binary, ThinVec::new())
}
AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
AssocOp::AssignOp(k) => {
let aop = match k {
token::Plus => BinOpKind::Add,
token::Minus => BinOpKind::Sub,
token::Star => BinOpKind::Mul,
token::Slash => BinOpKind::Div,
token::Percent => BinOpKind::Rem,
token::Caret => BinOpKind::BitXor,
token::And => BinOpKind::BitAnd,
token::Or => BinOpKind::BitOr,
token::Shl => BinOpKind::Shl,
token::Shr => BinOpKind::Shr,
};
let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
self.mk_expr(span, aopexpr, ThinVec::new())
}
AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
self.bug("AssocOp should have been handled by special case")
}
};
if let Fixity::None = fixity { break }
}
Ok(lhs)
}
fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
-> PResult<'a, P<Expr>> {
let mk_expr = |this: &mut Self, rhs: P<Ty>| {
this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
};
// Save the state of the parser before parsing type normally, in case there is a
// LessThan comparison after this cast.
let parser_snapshot_before_type = self.clone();
match self.parse_ty_no_plus() {
Ok(rhs) => {
Ok(mk_expr(self, rhs))
}
Err(mut type_err) => {
// Rewind to before attempting to parse the type with generics, to recover
// from situations like `x as usize < y` in which we first tried to parse
// `usize < y` as a type with generic arguments.
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
match self.parse_path(PathStyle::Expr) {
Ok(path) => {
let (op_noun, op_verb) = match self.token.kind {
token::Lt => ("comparison", "comparing"),
token::BinOp(token::Shl) => ("shift", "shifting"),
_ => {
// We can end up here even without `<` being the next token, for
// example because `parse_ty_no_plus` returns `Err` on keywords,
// but `parse_path` returns `Ok` on them due to error recovery.
// Return original error and parser state.
mem::replace(self, parser_snapshot_after_type);
return Err(type_err);
}
};
// Successfully parsed the type path leaving a `<` yet to parse.
type_err.cancel();
// Report non-fatal diagnostics, keep `x as usize` as an expression
// in AST and continue parsing.
let msg = format!("`<` is interpreted as a start of generic \
arguments for `{}`, not a {}", path, op_noun);
let mut err =
self.sess.span_diagnostic.struct_span_err(self.token.span, &msg);
let span_after_type = parser_snapshot_after_type.token.span;
err.span_label(self.look_ahead(1, |t| t.span).to(span_after_type),
"interpreted as generic arguments");
err.span_label(self.token.span, format!("not interpreted as {}", op_noun));
let expr = mk_expr(self, P(Ty {
span: path.span,
node: TyKind::Path(None, path),
id: ast::DUMMY_NODE_ID
}));
let expr_str = self.sess.source_map().span_to_snippet(expr.span)
.unwrap_or_else(|_| pprust::expr_to_string(&expr));
err.span_suggestion(
expr.span,
&format!("try {} the cast value", op_verb),
format!("({})", expr_str),
Applicability::MachineApplicable
);
err.emit();
Ok(expr)
}
Err(mut path_err) => {
// Couldn't parse as a path, return original error and parser state.
path_err.cancel();
mem::replace(self, parser_snapshot_after_type);
Err(type_err)
}
}
}
}
}
/// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
fn parse_prefix_range_expr(&mut self,
already_parsed_attrs: Option<ThinVec<Attribute>>)
-> PResult<'a, P<Expr>> {
// Check for deprecated `...` syntax
if self.token == token::DotDotDot {
self.err_dotdotdot_syntax(self.token.span);
}
debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
"parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
self.token);
let tok = self.token.clone();
let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
let lo = self.token.span;
let mut hi = self.token.span;
self.bump();
let opt_end = if self.is_at_start_of_range_notation_rhs() {
// RHS must be parsed with more associativity than the dots.
let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
Some(self.parse_assoc_expr_with(next_prec,
LhsExpr::NotYetParsed)
.map(|x|{
hi = x.span;
x
})?)
} else {
None
};
let limits = if tok == token::DotDot {
RangeLimits::HalfOpen
} else {
RangeLimits::Closed
};
let r = self.mk_range(None, opt_end, limits)?;
Ok(self.mk_expr(lo.to(hi), r, attrs))
}
fn is_at_start_of_range_notation_rhs(&self) -> bool {
if self.token.can_begin_expr() {
// parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
if self.token == token::OpenDelim(token::Brace) {
return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
}
true
} else {
false
}
}
/// Parses an `if` or `if let` expression (`if` token already eaten).
fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.check_keyword(kw::Let) {
return self.parse_if_let_expr(attrs);
}
let lo = self.prev_span;
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
// Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
// verify that the last statement is either an implicit return (no `;`) or an explicit
// return. This won't catch blocks with an explicit `return`, but that would be caught by
// the dead code lint.
if self.eat_keyword(kw::Else) || !cond.returns() {
let sp = self.sess.source_map().next_point(lo);
let mut err = self.diagnostic()
.struct_span_err(sp, "missing condition for `if` statemement");
err.span_label(sp, "expected if condition here");
return Err(err)
}
let not_block = self.token != token::OpenDelim(token::Brace);
let thn = self.parse_block().map_err(|mut err| {
if not_block {
err.span_label(lo, "this `if` statement has a condition, but no block");
}
err
})?;
let mut els: Option<P<Expr>> = None;
let mut hi = thn.span;
if self.eat_keyword(kw::Else) {
let elexpr = self.parse_else_expr()?;
hi = elexpr.span;
els = Some(elexpr);
}
Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
}
/// Parses an `if let` expression (`if` token already eaten).
fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>> {
let lo = self.prev_span;
self.expect_keyword(kw::Let)?;
let pats = self.parse_pats()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let thn = self.parse_block()?;
let (hi, els) = if self.eat_keyword(kw::Else) {
let expr = self.parse_else_expr()?;
(expr.span, Some(expr))
} else {
(thn.span, None)
};
Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
}
/// Parses `move |args| expr`.
fn parse_lambda_expr(&mut self,
attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let lo = self.token.span;
let movability = if self.eat_keyword(kw::Static) {
Movability::Static
} else {
Movability::Movable
};
let asyncness = if self.token.span.rust_2018() {
self.parse_asyncness()
} else {
IsAsync::NotAsync
};
let capture_clause = if self.eat_keyword(kw::Move) {
CaptureBy::Value
} else {
CaptureBy::Ref
};
let decl = self.parse_fn_block_decl()?;
let decl_hi = self.prev_span;
let body = match decl.output {
FunctionRetTy::Default(_) => {
let restrictions = self.restrictions - Restrictions::STMT_EXPR;
self.parse_expr_res(restrictions, None)?
},
_ => {
// If an explicit return type is given, require a
// block to appear (RFC 968).
let body_lo = self.token.span;
self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
}
};
Ok(self.mk_expr(
lo.to(body.span),
ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
attrs))
}
// `else` token already eaten
fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
if self.eat_keyword(kw::If) {
return self.parse_if_expr(ThinVec::new());
} else {
let blk = self.parse_block()?;
return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
}
}
/// Parse a 'for' .. 'in' expression ('for' token already eaten)
fn parse_for_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
// Parse: `for <src_pat> in <src_expr> <src_loop_block>`
let pat = self.parse_top_level_pat()?;
if !self.eat_keyword(kw::In) {
let in_span = self.prev_span.between(self.token.span);
let mut err = self.sess.span_diagnostic
.struct_span_err(in_span, "missing `in` in `for` loop");
err.span_suggestion_short(
in_span, "try adding `in` here", " in ".into(),
// has been misleading, at least in the past (closed Issue #48492)
Applicability::MaybeIncorrect
);
err.emit();
}
let in_span = self.prev_span;
self.check_for_for_in_in_typo(in_span);
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let hi = self.prev_span;
Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
}
/// Parses a `while` or `while let` expression (`while` token already eaten).
fn parse_while_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
if self.token.is_keyword(kw::Let) {
return self.parse_while_let_expr(opt_label, span_lo, attrs);
}
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
}
/// Parses a `while let` expression (`while` token already eaten).
fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
self.expect_keyword(kw::Let)?;
let pats = self.parse_pats()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
}
// parse `loop {...}`, `loop` token already eaten
fn parse_loop_expr(&mut self, opt_label: Option<Label>,
span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let span = span_lo.to(body.span);
Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
}
/// Parses an `async move {...}` expression.
pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let span_lo = self.token.span;
self.expect_keyword(kw::Async)?;
let capture_clause = if self.eat_keyword(kw::Move) {
CaptureBy::Value
} else {
CaptureBy::Ref
};
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
Ok(self.mk_expr(
span_lo.to(body.span),
ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
}
/// Parses a `try {...}` expression (`try` token already eaten).
fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
-> PResult<'a, P<Expr>>
{
let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
if self.eat_keyword(kw::Catch) {
let mut error = self.struct_span_err(self.prev_span,
"keyword `catch` cannot follow a `try` block");
error.help("try using `match` on the result of the `try` block instead");
error.emit();
Err(error)
} else {
Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
}
}
// `match` token already eaten
fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let match_span = self.prev_span;
let lo = self.prev_span;
let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
None)?;
if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
if self.token == token::Semi {
e.span_suggestion_short(
match_span,
"try removing this `match`",
String::new(),
Applicability::MaybeIncorrect // speculative
);
}
return Err(e)
}
attrs.extend(self.parse_inner_attributes()?);
let mut arms: Vec<Arm> = Vec::new();
while self.token != token::CloseDelim(token::Brace) {
match self.parse_arm() {
Ok(arm) => arms.push(arm),
Err(mut e) => {
// Recover by skipping to the end of the block.
e.emit();
self.recover_stmt();
let span = lo.to(self.token.span);
if self.token == token::CloseDelim(token::Brace) {
self.bump();
}
return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
}
}
}
let hi = self.token.span;
self.bump();
return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
}
crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
let attrs = self.parse_outer_attributes()?;
let lo = self.token.span;
let pats = self.parse_pats()?;
let guard = if self.eat_keyword(kw::If) {
Some(Guard::If(self.parse_expr()?))
} else {
None
};
let arrow_span = self.token.span;
self.expect(&token::FatArrow)?;
let arm_start_span = self.token.span;
let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
.map_err(|mut err| {
err.span_label(arrow_span, "while parsing the `match` arm starting here");
err
})?;
let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
&& self.token != token::CloseDelim(token::Brace);
let hi = self.token.span;
if require_comma {
let cm = self.sess.source_map();
self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
.map_err(|mut err| {
match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
(Ok(ref expr_lines), Ok(ref arm_start_lines))
if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
&& expr_lines.lines.len() == 2
&& self.token == token::FatArrow => {
// We check whether there's any trailing code in the parse span,
// if there isn't, we very likely have the following:
//
// X | &Y => "y"
// | -- - missing comma