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Move 'probably equal' methods to librustc_parse
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This is preparation for PR #73084
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@Aaron1011
Aaron1011 committed Aug 2, 2020
1 parent 5ef872f commit 183947f
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Showing 5 changed files with 187 additions and 184 deletions.
1 change: 1 addition & 0 deletions Cargo.lock
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Expand Up @@ -3808,6 +3808,7 @@ dependencies = [
"rustc_lexer",
"rustc_session",
"rustc_span",
"smallvec 1.4.0",
"tracing",
"unicode-normalization",
]
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56 changes: 0 additions & 56 deletions src/librustc_ast/token.rs
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Expand Up @@ -673,62 +673,6 @@ impl Token {

Some(Token::new(kind, self.span.to(joint.span)))
}

// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
crate fn probably_equal_for_proc_macro(&self, other: &Token) -> bool {
if mem::discriminant(&self.kind) != mem::discriminant(&other.kind) {
return false;
}
match (&self.kind, &other.kind) {
(&Eq, &Eq)
| (&Lt, &Lt)
| (&Le, &Le)
| (&EqEq, &EqEq)
| (&Ne, &Ne)
| (&Ge, &Ge)
| (&Gt, &Gt)
| (&AndAnd, &AndAnd)
| (&OrOr, &OrOr)
| (&Not, &Not)
| (&Tilde, &Tilde)
| (&At, &At)
| (&Dot, &Dot)
| (&DotDot, &DotDot)
| (&DotDotDot, &DotDotDot)
| (&DotDotEq, &DotDotEq)
| (&Comma, &Comma)
| (&Semi, &Semi)
| (&Colon, &Colon)
| (&ModSep, &ModSep)
| (&RArrow, &RArrow)
| (&LArrow, &LArrow)
| (&FatArrow, &FatArrow)
| (&Pound, &Pound)
| (&Dollar, &Dollar)
| (&Question, &Question)
| (&Whitespace, &Whitespace)
| (&Comment, &Comment)
| (&Eof, &Eof) => true,

(&BinOp(a), &BinOp(b)) | (&BinOpEq(a), &BinOpEq(b)) => a == b,

(&OpenDelim(a), &OpenDelim(b)) | (&CloseDelim(a), &CloseDelim(b)) => a == b,

(&DocComment(a), &DocComment(b)) | (&Shebang(a), &Shebang(b)) => a == b,

(&Literal(a), &Literal(b)) => a == b,

(&Lifetime(a), &Lifetime(b)) => a == b,
(&Ident(a, b), &Ident(c, d)) => {
b == d && (a == c || a == kw::DollarCrate || c == kw::DollarCrate)
}

(&Interpolated(..), &Interpolated(..)) => false,

_ => panic!("forgot to add a token?"),
}
}
}

impl PartialEq<TokenKind> for Token {
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125 changes: 0 additions & 125 deletions src/librustc_ast/tokenstream.rs
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Expand Up @@ -21,8 +21,6 @@ use rustc_macros::HashStable_Generic;
use rustc_span::{Span, DUMMY_SP};
use smallvec::{smallvec, SmallVec};

use log::debug;

use std::{iter, mem};

/// When the main rust parser encounters a syntax-extension invocation, it
Expand Down Expand Up @@ -68,23 +66,6 @@ impl TokenTree {
}
}

// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
//
// This is otherwise the same as `eq_unspanned`, only recursing with a
// different method.
pub fn probably_equal_for_proc_macro(&self, other: &TokenTree) -> bool {
match (self, other) {
(TokenTree::Token(token), TokenTree::Token(token2)) => {
token.probably_equal_for_proc_macro(token2)
}
(TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
delim == delim2 && tts.probably_equal_for_proc_macro(&tts2)
}
_ => false,
}
}

/// Retrieves the TokenTree's span.
pub fn span(&self) -> Span {
match self {
Expand Down Expand Up @@ -307,112 +288,6 @@ impl TokenStream {
t1.next().is_none() && t2.next().is_none()
}

// See comments in `Nonterminal::to_tokenstream` for why we care about
// *probably* equal here rather than actual equality
//
// This is otherwise the same as `eq_unspanned`, only recursing with a
// different method.
pub fn probably_equal_for_proc_macro(&self, other: &TokenStream) -> bool {
// When checking for `probably_eq`, we ignore certain tokens that aren't
// preserved in the AST. Because they are not preserved, the pretty
// printer arbitrarily adds or removes them when printing as token
// streams, making a comparison between a token stream generated from an
// AST and a token stream which was parsed into an AST more reliable.
fn semantic_tree(tree: &TokenTree) -> bool {
if let TokenTree::Token(token) = tree {
if let
// The pretty printer tends to add trailing commas to
// everything, and in particular, after struct fields.
| token::Comma
// The pretty printer emits `NoDelim` as whitespace.
| token::OpenDelim(DelimToken::NoDelim)
| token::CloseDelim(DelimToken::NoDelim)
// The pretty printer collapses many semicolons into one.
| token::Semi
// The pretty printer collapses whitespace arbitrarily and can
// introduce whitespace from `NoDelim`.
| token::Whitespace
// The pretty printer can turn `$crate` into `::crate_name`
| token::ModSep = token.kind {
return false;
}
}
true
}

// When comparing two `TokenStream`s, we ignore the `IsJoint` information.
//
// However, `rustc_parse::lexer::tokentrees::TokenStreamBuilder` will
// use `Token.glue` on adjacent tokens with the proper `IsJoint`.
// Since we are ignoreing `IsJoint`, a 'glued' token (e.g. `BinOp(Shr)`)
// and its 'split'/'unglued' compoenents (e.g. `Gt, Gt`) are equivalent
// when determining if two `TokenStream`s are 'probably equal'.
//
// Therefore, we use `break_two_token_op` to convert all tokens
// to the 'unglued' form (if it exists). This ensures that two
// `TokenStream`s which differ only in how their tokens are glued
// will be considered 'probably equal', which allows us to keep spans.
//
// This is important when the original `TokenStream` contained
// extra spaces (e.g. `f :: < Vec < _ > > ( ) ;'). These extra spaces
// will be omitted when we pretty-print, which can cause the original
// and reparsed `TokenStream`s to differ in the assignment of `IsJoint`,
// leading to some tokens being 'glued' together in one stream but not
// the other. See #68489 for more details.
fn break_tokens(tree: TokenTree) -> impl Iterator<Item = TokenTree> {
// In almost all cases, we should have either zero or one levels
// of 'unglueing'. However, in some unusual cases, we may need
// to iterate breaking tokens mutliple times. For example:
// '[BinOpEq(Shr)] => [Gt, Ge] -> [Gt, Gt, Eq]'
let mut token_trees: SmallVec<[_; 2]>;
if let TokenTree::Token(token) = &tree {
let mut out = SmallVec::<[_; 2]>::new();
out.push(token.clone());
// Iterate to fixpoint:
// * We start off with 'out' containing our initial token, and `temp` empty
// * If we are able to break any tokens in `out`, then `out` will have
// at least one more element than 'temp', so we will try to break tokens
// again.
// * If we cannot break any tokens in 'out', we are done
loop {
let mut temp = SmallVec::<[_; 2]>::new();
let mut changed = false;

for token in out.into_iter() {
if let Some((first, second)) = token.kind.break_two_token_op() {
temp.push(Token::new(first, DUMMY_SP));
temp.push(Token::new(second, DUMMY_SP));
changed = true;
} else {
temp.push(token);
}
}
out = temp;
if !changed {
break;
}
}
token_trees = out.into_iter().map(TokenTree::Token).collect();
if token_trees.len() != 1 {
debug!("break_tokens: broke {:?} to {:?}", tree, token_trees);
}
} else {
token_trees = SmallVec::new();
token_trees.push(tree);
}
token_trees.into_iter()
}

let mut t1 = self.trees().filter(semantic_tree).flat_map(break_tokens);
let mut t2 = other.trees().filter(semantic_tree).flat_map(break_tokens);
for (t1, t2) in t1.by_ref().zip(t2.by_ref()) {
if !t1.probably_equal_for_proc_macro(&t2) {
return false;
}
}
t1.next().is_none() && t2.next().is_none()
}

pub fn map_enumerated<F: FnMut(usize, TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
TokenStream(Lrc::new(
self.0
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1 change: 1 addition & 0 deletions src/librustc_parse/Cargo.toml
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Expand Up @@ -21,3 +21,4 @@ rustc_session = { path = "../librustc_session" }
rustc_span = { path = "../librustc_span" }
rustc_ast = { path = "../librustc_ast" }
unicode-normalization = "0.1.11"
smallvec = { version = "1.0", features = ["union", "may_dangle"] }

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