diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs index 05156745105..dc80dab8c6c 100644 --- a/compiler/rustc_parse/src/parser/expr.rs +++ b/compiler/rustc_parse/src/parser/expr.rs @@ -1,9 +1,12 @@ use super::pat::{RecoverColon, RecoverComma, PARAM_EXPECTED}; use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign}; -use super::{AttrWrapper, BlockMode, ForceCollect, Parser, PathStyle, Restrictions, TokenType}; +use super::{ + AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions, TokenType, +}; use super::{SemiColonMode, SeqSep, TokenExpectType, TrailingToken}; use crate::maybe_recover_from_interpolated_ty_qpath; +use ast::token::DelimToken; use rustc_ast::ptr::P; use rustc_ast::token::{self, Token, TokenKind}; use rustc_ast::tokenstream::Spacing; @@ -91,6 +94,8 @@ impl<'a> Parser<'a> { /// Parses an expression. #[inline] pub fn parse_expr(&mut self) -> PResult<'a, P> { + self.current_closure.take(); + self.parse_expr_res(Restrictions::empty(), None) } @@ -1736,7 +1741,7 @@ impl<'a> Parser<'a> { let capture_clause = self.parse_capture_clause()?; let decl = self.parse_fn_block_decl()?; let decl_hi = self.prev_token.span; - let body = match decl.output { + let mut body = match decl.output { FnRetTy::Default(_) => { let restrictions = self.restrictions - Restrictions::STMT_EXPR; self.parse_expr_res(restrictions, None)? @@ -1753,11 +1758,28 @@ impl<'a> Parser<'a> { self.sess.gated_spans.gate(sym::async_closure, span); } - Ok(self.mk_expr( + if self.token.kind == TokenKind::Semi && self.token_cursor.frame.delim == DelimToken::Paren + { + // It is likely that the closure body is a block but where the + // braces have been removed. We will recover and eat the next + // statements later in the parsing process. + body = self.mk_expr_err(body.span); + } + + let body_span = body.span; + + let closure = self.mk_expr( lo.to(body.span), ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)), attrs, - )) + ); + + // Disable recovery for closure body + let spans = + ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span }; + self.current_closure = Some(spans); + + Ok(closure) } /// Parses an optional `move` prefix to a closure-like construct. diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index c4419e995ed..5c701fefd17 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -142,6 +142,17 @@ pub struct Parser<'a> { /// If present, this `Parser` is not parsing Rust code but rather a macro call. subparser_name: Option<&'static str>, capture_state: CaptureState, + /// This allows us to recover when the user forget to add braces around + /// multiple statements in the closure body. + pub current_closure: Option, +} + +/// Stores span informations about a closure. +#[derive(Clone)] +pub struct ClosureSpans { + pub whole_closure: Span, + pub closing_pipe: Span, + pub body: Span, } /// Indicates a range of tokens that should be replaced by @@ -440,6 +451,7 @@ impl<'a> Parser<'a> { replace_ranges: Vec::new(), inner_attr_ranges: Default::default(), }, + current_closure: None, }; // Make parser point to the first token. @@ -761,8 +773,11 @@ impl<'a> Parser<'a> { first = false; } else { match self.expect(t) { - Ok(false) => {} + Ok(false) => { + self.current_closure.take(); + } Ok(true) => { + self.current_closure.take(); recovered = true; break; } @@ -770,10 +785,29 @@ impl<'a> Parser<'a> { let sp = self.prev_token.span.shrink_to_hi(); let token_str = pprust::token_kind_to_string(t); - // Attempt to keep parsing if it was a similar separator. - if let Some(ref tokens) = t.similar_tokens() { - if tokens.contains(&self.token.kind) && !unclosed_delims { - self.bump(); + match self.current_closure.take() { + Some(closure_spans) if self.token.kind == TokenKind::Semi => { + // Finding a semicolon instead of a comma + // after a closure body indicates that the + // closure body may be a block but the user + // forgot to put braces around its + // statements. + + self.recover_missing_braces_around_closure_body( + closure_spans, + expect_err, + )?; + + continue; + } + + _ => { + // Attempt to keep parsing if it was a similar separator. + if let Some(ref tokens) = t.similar_tokens() { + if tokens.contains(&self.token.kind) && !unclosed_delims { + self.bump(); + } + } } } @@ -839,6 +873,65 @@ impl<'a> Parser<'a> { Ok((v, trailing, recovered)) } + fn recover_missing_braces_around_closure_body( + &mut self, + closure_spans: ClosureSpans, + mut expect_err: DiagnosticBuilder<'_>, + ) -> PResult<'a, ()> { + let initial_semicolon = self.token.span; + + while self.eat(&TokenKind::Semi) { + let _ = self.parse_stmt(ForceCollect::Yes)?; + } + + expect_err.set_primary_message( + "closure bodies that contain statements must be surrounded by braces", + ); + + let preceding_pipe_span = closure_spans.closing_pipe; + let following_token_span = self.token.span; + + let mut first_note = MultiSpan::from(vec![initial_semicolon]); + first_note.push_span_label( + initial_semicolon, + "this `;` turns the preceding closure into a statement".to_string(), + ); + first_note.push_span_label( + closure_spans.body, + "this expression is a statement because of the trailing semicolon".to_string(), + ); + expect_err.span_note(first_note, "statement found outside of a block"); + + let mut second_note = MultiSpan::from(vec![closure_spans.whole_closure]); + second_note.push_span_label( + closure_spans.whole_closure, + "this is the parsed closure...".to_string(), + ); + second_note.push_span_label( + following_token_span, + "...but likely you meant the closure to end here".to_string(), + ); + expect_err.span_note(second_note, "the closure body may be incorrectly delimited"); + + expect_err.set_span(vec![preceding_pipe_span, following_token_span]); + + let opening_suggestion_str = " {".to_string(); + let closing_suggestion_str = "}".to_string(); + + expect_err.multipart_suggestion( + "try adding braces", + vec![ + (preceding_pipe_span.shrink_to_hi(), opening_suggestion_str), + (following_token_span.shrink_to_lo(), closing_suggestion_str), + ], + Applicability::MaybeIncorrect, + ); + + expect_err.emit(); + + Ok(()) + } + /// Parses a sequence, not including the closing delimiter. The function /// `f` must consume tokens until reaching the next separator or /// closing bracket. diff --git a/src/test/ui/expr/malformed_closure/missing_braces_around_block.fixed b/src/test/ui/expr/malformed_closure/missing_braces_around_block.fixed new file mode 100644 index 00000000000..c50b9a12b6d --- /dev/null +++ b/src/test/ui/expr/malformed_closure/missing_braces_around_block.fixed @@ -0,0 +1,19 @@ +// This snippet ensures that no attempt to recover on a semicolon instead of +// comma is made next to a closure body. +// +// If this recovery happens, then plenty of errors are emitted. Here, we expect +// only one error. +// +// This is part of issue #88065: +// https://github.com/rust-lang/rust/issues/88065 + +// run-rustfix + +fn main() { + let num = 5; + (1..num).reduce(|a, b| { + //~^ ERROR: closure bodies that contain statements must be surrounded by braces + println!("{}", a); + a * b + }).unwrap(); +} diff --git a/src/test/ui/expr/malformed_closure/missing_braces_around_block.rs b/src/test/ui/expr/malformed_closure/missing_braces_around_block.rs new file mode 100644 index 00000000000..58c81f3a6e2 --- /dev/null +++ b/src/test/ui/expr/malformed_closure/missing_braces_around_block.rs @@ -0,0 +1,19 @@ +// This snippet ensures that no attempt to recover on a semicolon instead of +// comma is made next to a closure body. +// +// If this recovery happens, then plenty of errors are emitted. Here, we expect +// only one error. +// +// This is part of issue #88065: +// https://github.com/rust-lang/rust/issues/88065 + +// run-rustfix + +fn main() { + let num = 5; + (1..num).reduce(|a, b| + //~^ ERROR: closure bodies that contain statements must be surrounded by braces + println!("{}", a); + a * b + ).unwrap(); +} diff --git a/src/test/ui/expr/malformed_closure/missing_braces_around_block.stderr b/src/test/ui/expr/malformed_closure/missing_braces_around_block.stderr new file mode 100644 index 00000000000..dac9a8cfc69 --- /dev/null +++ b/src/test/ui/expr/malformed_closure/missing_braces_around_block.stderr @@ -0,0 +1,38 @@ +error: closure bodies that contain statements must be surrounded by braces + --> $DIR/missing_braces_around_block.rs:14:26 + | +LL | (1..num).reduce(|a, b| + | ^ +... +LL | ).unwrap(); + | ^ + | +note: statement found outside of a block + --> $DIR/missing_braces_around_block.rs:16:26 + | +LL | println!("{}", a); + | -----------------^ this `;` turns the preceding closure into a statement + | | + | this expression is a statement because of the trailing semicolon +note: the closure body may be incorrectly delimited + --> $DIR/missing_braces_around_block.rs:14:21 + | +LL | (1..num).reduce(|a, b| + | _____________________^ +LL | | +LL | | println!("{}", a); + | |_________________________^ this is the parsed closure... +LL | a * b +LL | ).unwrap(); + | - ...but likely you meant the closure to end here +help: try adding braces + | +LL ~ (1..num).reduce(|a, b| { +LL | +LL | println!("{}", a); +LL | a * b +LL ~ }).unwrap(); + | + +error: aborting due to previous error + diff --git a/src/test/ui/expr/malformed_closure/ruby_style_closure.rs b/src/test/ui/expr/malformed_closure/ruby_style_closure.rs new file mode 100644 index 00000000000..e4341e19687 --- /dev/null +++ b/src/test/ui/expr/malformed_closure/ruby_style_closure.rs @@ -0,0 +1,16 @@ +// Part of issue #27300. +// The problem here is that ruby-style closures are parsed as blocks whose +// first statement is a closure. See the issue for more details: +// https://github.com/rust-lang/rust/issues/27300 + +// Note: this test represents what the compiler currently emits. The error +// message will be improved later. + +fn main() { + let p = Some(45).and_then({ + //~^ expected a `FnOnce<({integer},)>` closure, found `Option<_>` + |x| println!("doubling {}", x); + Some(x * 2) + //~^ ERROR: cannot find value `x` in this scope + }); +} diff --git a/src/test/ui/expr/malformed_closure/ruby_style_closure.stderr b/src/test/ui/expr/malformed_closure/ruby_style_closure.stderr new file mode 100644 index 00000000000..99df0632b4c --- /dev/null +++ b/src/test/ui/expr/malformed_closure/ruby_style_closure.stderr @@ -0,0 +1,18 @@ +error[E0425]: cannot find value `x` in this scope + --> $DIR/ruby_style_closure.rs:13:14 + | +LL | Some(x * 2) + | ^ not found in this scope + +error[E0277]: expected a `FnOnce<({integer},)>` closure, found `Option<_>` + --> $DIR/ruby_style_closure.rs:10:22 + | +LL | let p = Some(45).and_then({ + | ^^^^^^^^ expected an `FnOnce<({integer},)>` closure, found `Option<_>` + | + = help: the trait `FnOnce<({integer},)>` is not implemented for `Option<_>` + +error: aborting due to 2 previous errors + +Some errors have detailed explanations: E0277, E0425. +For more information about an error, try `rustc --explain E0277`.