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internal: overhaul expression attribute parsing #10354

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Merged
merged 2 commits into from
Sep 26, 2021
Merged

internal: overhaul expression attribute parsing #10354

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7dc331f
fix: correct extend_to logic in parser
matklad Sep 25, 2021
56964c9
feat: allow attributes on all expressions
matklad Sep 25, 2021
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6 changes: 4 additions & 2 deletions crates/hir_def/src/body/lower.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -650,8 +650,10 @@ impl ExprCollector<'_> {
self.statements_in_scope.push(Statement::Let { pat, type_ref, initializer });
}
ast::Stmt::ExprStmt(stmt) => {
if self.check_cfg(&stmt).is_none() {
return;
if let Some(expr) = stmt.expr() {
if self.check_cfg(&expr).is_none() {
return;
}
}
let has_semi = stmt.semicolon_token().is_some();
// Note that macro could be expended to multiple statements
Expand Down
10 changes: 4 additions & 6 deletions crates/parser/src/event.rs
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Expand Up @@ -93,8 +93,6 @@ pub(super) fn process(sink: &mut dyn TreeSink, mut events: Vec<Event>) {

for i in 0..events.len() {
match mem::replace(&mut events[i], Event::tombstone()) {
Event::Start { kind: TOMBSTONE, .. } => (),

Event::Start { kind, forward_parent } => {
// For events[A, B, C], B is A's forward_parent, C is B's forward_parent,
// in the normal control flow, the parent-child relation: `A -> B -> C`,
Expand All @@ -109,9 +107,7 @@ pub(super) fn process(sink: &mut dyn TreeSink, mut events: Vec<Event>) {
// append `A`'s forward_parent `B`
fp = match mem::replace(&mut events[idx], Event::tombstone()) {
Event::Start { kind, forward_parent } => {
if kind != TOMBSTONE {
forward_parents.push(kind);
}
forward_parents.push(kind);
forward_parent
}
_ => unreachable!(),
Expand All @@ -120,7 +116,9 @@ pub(super) fn process(sink: &mut dyn TreeSink, mut events: Vec<Event>) {
}

for kind in forward_parents.drain(..).rev() {
sink.start_node(kind);
if kind != TOMBSTONE {
sink.start_node(kind);
}
}
}
Event::Finish => sink.finish_node(),
Expand Down
2 changes: 1 addition & 1 deletion crates/parser/src/grammar.rs
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Expand Up @@ -63,7 +63,7 @@ pub(crate) mod entry_points {
pub(crate) use types::type_;

pub(crate) fn expr(p: &mut Parser) {
let _ = expressions::expr_with_attrs(p);
let _ = expressions::expr(p);
}

pub(crate) fn stmt(p: &mut Parser) {
Expand Down
2 changes: 1 addition & 1 deletion crates/parser/src/grammar/attributes.rs
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Expand Up @@ -41,7 +41,7 @@ pub(super) fn meta(p: &mut Parser) {
match p.current() {
T![=] => {
p.bump(T![=]);
if expressions::expr(p).0.is_none() {
if !expressions::expr(p) {
p.error("expected expression");
}
}
Expand Down
145 changes: 62 additions & 83 deletions crates/parser/src/grammar/expressions.rs
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Expand Up @@ -13,35 +13,19 @@ pub(super) enum StmtWithSemi {

const EXPR_FIRST: TokenSet = LHS_FIRST;

pub(super) fn expr(p: &mut Parser) -> (Option<CompletedMarker>, BlockLike) {
pub(super) fn expr(p: &mut Parser) -> bool {
let r = Restrictions { forbid_structs: false, prefer_stmt: false };
expr_bp(p, r, 1)
expr_bp(p, None, r, 1).is_some()
}

pub(super) fn expr_with_attrs(p: &mut Parser) -> bool {
let m = p.start();
let has_attrs = p.at(T![#]);
attributes::outer_attrs(p);

let (cm, _block_like) = expr(p);
let success = cm.is_some();

match (has_attrs, cm) {
(true, Some(cm)) => cm.extend_to(p, m),
_ => m.abandon(p),
}

success
}

pub(super) fn expr_stmt(p: &mut Parser) -> (Option<CompletedMarker>, BlockLike) {
pub(super) fn expr_stmt(p: &mut Parser, m: Option<Marker>) -> Option<(CompletedMarker, BlockLike)> {
let r = Restrictions { forbid_structs: false, prefer_stmt: true };
expr_bp(p, r, 1)
expr_bp(p, m, r, 1)
}

fn expr_no_struct(p: &mut Parser) {
let r = Restrictions { forbid_structs: true, prefer_stmt: false };
expr_bp(p, r, 1);
expr_bp(p, None, r, 1);
}

pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi, prefer_expr: bool) {
Expand All @@ -53,7 +37,6 @@ pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi, prefer_expr: bool) {
// #[C] #[D] {}
// #[D] return ();
// }
let has_attrs = p.at(T![#]);
attributes::outer_attrs(p);

if p.at(T![let]) {
Expand All @@ -68,61 +51,39 @@ pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi, prefer_expr: bool) {
Err(m) => m,
};

let (cm, blocklike) = expr_stmt(p);
let kind = cm.as_ref().map(|cm| cm.kind()).unwrap_or(ERROR);

if has_attrs {
if matches!(kind, BIN_EXPR | RANGE_EXPR) {
// test_err attr_on_expr_not_allowed
if let Some((cm, blocklike)) = expr_stmt(p, Some(m)) {
if !(p.at(T!['}']) || (prefer_expr && p.at(EOF))) {
// test no_semi_after_block
// fn foo() {
// #[A] 1 + 2;
// #[B] if true {};
// if true {}
// loop {}
// match () {}
// while true {}
// for _ in () {}
// {}
// {}
// macro_rules! test {
// () => {}
// }
// test!{}
// }
p.error(format!("attributes are not allowed on {:?}", kind));
}
}

if p.at(T!['}']) || (prefer_expr && p.at(EOF)) {
// test attr_on_last_expr_in_block
// fn foo() {
// { #[A] bar!()? }
// #[B] &()
// }
match cm {
Some(cm) => cm.extend_to(p, m),
None => m.abandon(p),
}
} else {
// test no_semi_after_block
// fn foo() {
// if true {}
// loop {}
// match () {}
// while true {}
// for _ in () {}
// {}
// {}
// macro_rules! test {
// () => {}
// }
// test!{}
// }

match with_semi {
StmtWithSemi::No => (),
StmtWithSemi::Optional => {
p.eat(T![;]);
}
StmtWithSemi::Yes => {
if blocklike.is_block() {
let m = cm.precede(p);
match with_semi {
StmtWithSemi::No => (),
StmtWithSemi::Optional => {
p.eat(T![;]);
} else {
p.expect(T![;]);
}
StmtWithSemi::Yes => {
if blocklike.is_block() {
p.eat(T![;]);
} else {
p.expect(T![;]);
}
}
}
}

m.complete(p, EXPR_STMT);
m.complete(p, EXPR_STMT);
}
}

// test let_stmt
Expand All @@ -138,7 +99,7 @@ pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi, prefer_expr: bool) {
if p.eat(T![=]) {
// test let_stmt_init
// fn f() { let x = 92; }
expressions::expr_with_attrs(p);
expressions::expr(p);
}

match with_semi {
Expand Down Expand Up @@ -234,20 +195,34 @@ fn current_op(p: &Parser) -> (u8, SyntaxKind) {
}

// Parses expression with binding power of at least bp.
fn expr_bp(p: &mut Parser, mut r: Restrictions, bp: u8) -> (Option<CompletedMarker>, BlockLike) {
fn expr_bp(
p: &mut Parser,
m: Option<Marker>,
mut r: Restrictions,
bp: u8,
) -> Option<(CompletedMarker, BlockLike)> {
let m = m.unwrap_or_else(|| {
let m = p.start();
attributes::outer_attrs(p);
m
});
let mut lhs = match lhs(p, r) {
Some((lhs, blocklike)) => {
let lhs = lhs.extend_to(p, m);
if r.prefer_stmt && blocklike.is_block() {
// test stmt_bin_expr_ambiguity
// fn f() {
// let _ = {1} & 2;
// {1} &2;
// }
return (Some(lhs), BlockLike::Block);
return Some((lhs, BlockLike::Block));
}
lhs
}
None => return (None, BlockLike::NotBlock),
None => {
m.abandon(p);
return None;
}
};

loop {
Expand Down Expand Up @@ -285,10 +260,10 @@ fn expr_bp(p: &mut Parser, mut r: Restrictions, bp: u8) -> (Option<CompletedMark
}
}

expr_bp(p, Restrictions { prefer_stmt: false, ..r }, op_bp + 1);
expr_bp(p, None, Restrictions { prefer_stmt: false, ..r }, op_bp + 1);
lhs = m.complete(p, if is_range { RANGE_EXPR } else { BIN_EXPR });
}
(Some(lhs), BlockLike::NotBlock)
Some((lhs, BlockLike::NotBlock))
}

const LHS_FIRST: TokenSet =
Expand Down Expand Up @@ -341,9 +316,10 @@ fn lhs(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)>
m = p.start();
p.bump(op);
if p.at_ts(EXPR_FIRST) && !(r.forbid_structs && p.at(T!['{'])) {
expr_bp(p, r, 2);
expr_bp(p, None, r, 2);
}
return Some((m.complete(p, RANGE_EXPR), BlockLike::NotBlock));
let cm = m.complete(p, RANGE_EXPR);
return Some((cm, BlockLike::NotBlock));
}
}

Expand All @@ -353,12 +329,15 @@ fn lhs(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)>
// {p}.x = 10;
// }
let (lhs, blocklike) = atom::atom_expr(p, r)?;
return Some(postfix_expr(p, lhs, blocklike, !(r.prefer_stmt && blocklike.is_block())));
let (cm, block_like) =
postfix_expr(p, lhs, blocklike, !(r.prefer_stmt && blocklike.is_block()));
return Some((cm, block_like));
}
};
// parse the interior of the unary expression
expr_bp(p, r, 255);
Some((m.complete(p, kind), BlockLike::NotBlock))
expr_bp(p, None, r, 255);
let cm = m.complete(p, kind);
Some((cm, BlockLike::NotBlock))
}

fn postfix_expr(
Expand Down Expand Up @@ -536,7 +515,7 @@ fn arg_list(p: &mut Parser) {
// fn main() {
// foo(#[attr] 92)
// }
if !expr_with_attrs(p) {
if !expr(p) {
break;
}
if !p.at(T![')']) && !p.expect(T![,]) {
Expand Down
19 changes: 11 additions & 8 deletions crates/parser/src/grammar/expressions/atom.rs
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Expand Up @@ -176,7 +176,7 @@ fn tuple_expr(p: &mut Parser) -> CompletedMarker {

// test tuple_attrs
// const A: (i64, i64) = (1, #[cfg(test)] 2);
if !expr_with_attrs(p) {
if !expr(p) {
break;
}

Expand Down Expand Up @@ -209,7 +209,7 @@ fn array_expr(p: &mut Parser) -> CompletedMarker {

// test array_attrs
// const A: &[i64] = &[1, #[cfg(test)] 2];
if !expr_with_attrs(p) {
if !expr(p) {
break;
}

Expand Down Expand Up @@ -438,7 +438,10 @@ fn match_arm(p: &mut Parser) {
match_guard(p);
}
p.expect(T![=>]);
let blocklike = expr_stmt(p).1;
let blocklike = match expr_stmt(p, None) {
Some((_, blocklike)) => blocklike,
None => BlockLike::NotBlock,
};

// test match_arms_commas
// fn foo() {
Expand Down Expand Up @@ -619,14 +622,14 @@ fn meta_var_expr(p: &mut Parser) -> CompletedMarker {
assert!(p.at(L_DOLLAR));
let m = p.start();
p.bump(L_DOLLAR);
let (completed, _is_block) =
expr_bp(p, Restrictions { forbid_structs: false, prefer_stmt: false }, 1);
let expr = expr_bp(p, None, Restrictions { forbid_structs: false, prefer_stmt: false }, 1);

match (completed, p.current()) {
(Some(it), R_DOLLAR) => {
match (expr, p.current()) {
(Some((cm, _)), R_DOLLAR) => {
p.bump(R_DOLLAR);
// FIXME: this leaves the dollar hanging in the air...
m.abandon(p);
it
cm
}
_ => {
while !p.at(R_DOLLAR) {
Expand Down
13 changes: 9 additions & 4 deletions crates/parser/src/parser.rs
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Expand Up @@ -339,11 +339,16 @@ impl CompletedMarker {
}

/// Extends this completed marker *to the left* up to `m`.
pub(crate) fn extend_to(self, p: &mut Parser, mut m: Marker) {
assert!(m.pos <= self.pos);
pub(crate) fn extend_to(self, p: &mut Parser, mut m: Marker) -> CompletedMarker {
m.bomb.defuse();

p.events.swap(self.pos as usize, m.pos as usize);
let idx = m.pos as usize;
match &mut p.events[idx] {
Event::Start { forward_parent, .. } => {
*forward_parent = Some(self.pos - m.pos);
}
_ => unreachable!(),
}
self
}

pub(crate) fn kind(&self) -> SyntaxKind {
Expand Down
6 changes: 2 additions & 4 deletions crates/syntax/test_data/parser/err/0009_broken_struct_type_parameter.rast
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Expand Up @@ -26,9 +26,8 @@ SOURCE_FILE@0..43
PATH_SEGMENT@23..24
NAME_REF@23..24
IDENT@23..24 "f"
EXPR_STMT@24..25
ERROR@24..25
COLON@24..25 ":"
ERROR@24..25
COLON@24..25 ":"
WHITESPACE@25..26 " "
PATH_EXPR@26..29
PATH@26..29
Expand All @@ -55,4 +54,3 @@ error 15..15: expected an item
error 17..17: expected an item
error 24..24: expected SEMICOLON
error 24..24: expected expression
error 25..25: expected SEMICOLON
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