diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/expr.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/expr.rs | 381 |
1 files changed, 257 insertions, 124 deletions
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs index 9ae3ef617..f4cee3a66 100644 --- a/compiler/rustc_parse/src/parser/expr.rs +++ b/compiler/rustc_parse/src/parser/expr.rs @@ -8,6 +8,7 @@ use super::{ use crate::errors; use crate::maybe_recover_from_interpolated_ty_qpath; +use ast::mut_visit::{noop_visit_expr, MutVisitor}; use ast::{Path, PathSegment}; use core::mem; use rustc_ast::ptr::P; @@ -27,6 +28,7 @@ use rustc_errors::{ AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult, StashKey, }; +use rustc_macros::Subdiagnostic; use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded}; use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP; use rustc_session::lint::BuiltinLintDiagnostics; @@ -122,8 +124,8 @@ impl<'a> Parser<'a> { self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value }) } - fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> { - match self.parse_expr() { + fn parse_expr_catch_underscore(&mut self, restrictions: Restrictions) -> PResult<'a, P<Expr>> { + match self.parse_expr_res(restrictions, None) { Ok(expr) => Ok(expr), Err(mut err) => match self.token.ident() { Some((Ident { name: kw::Underscore, .. }, false)) @@ -141,7 +143,8 @@ impl<'a> Parser<'a> { /// Parses a sequence of expressions delimited by parentheses. fn parse_expr_paren_seq(&mut self) -> PResult<'a, ThinVec<P<Expr>>> { - self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r) + self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore(Restrictions::empty())) + .map(|(r, _)| r) } /// Parses an expression, subject to the given restrictions. @@ -1345,110 +1348,113 @@ impl<'a> Parser<'a> { // Outer attributes are already parsed and will be // added to the return value after the fact. - // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`. - let lo = self.token.span; - if let token::Literal(_) = 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. - self.parse_expr_lit() - } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) { - self.parse_expr_tuple_parens() - } else if self.check(&token::OpenDelim(Delimiter::Brace)) { - self.parse_expr_block(None, lo, BlockCheckMode::Default) - } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) { - self.parse_expr_closure().map_err(|mut err| { - // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }` - // then suggest parens around the lhs. - if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) { - err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp)); + let restrictions = self.restrictions; + self.with_res(restrictions - Restrictions::ALLOW_LET, |this| { + // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`. + let lo = this.token.span; + if let token::Literal(_) = this.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. + this.parse_expr_lit() + } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) { + this.parse_expr_tuple_parens(restrictions) + } else if this.check(&token::OpenDelim(Delimiter::Brace)) { + this.parse_expr_block(None, lo, BlockCheckMode::Default) + } else if this.check(&token::BinOp(token::Or)) || this.check(&token::OrOr) { + this.parse_expr_closure().map_err(|mut err| { + // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }` + // then suggest parens around the lhs. + if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) { + err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp)); + } + err + }) + } else if this.check(&token::OpenDelim(Delimiter::Bracket)) { + this.parse_expr_array_or_repeat(Delimiter::Bracket) + } else if this.is_builtin() { + this.parse_expr_builtin() + } else if this.check_path() { + this.parse_expr_path_start() + } else if this.check_keyword(kw::Move) + || this.check_keyword(kw::Static) + || this.check_const_closure() + { + this.parse_expr_closure() + } else if this.eat_keyword(kw::If) { + this.parse_expr_if() + } else if this.check_keyword(kw::For) { + if this.choose_generics_over_qpath(1) { + this.parse_expr_closure() + } else { + assert!(this.eat_keyword(kw::For)); + this.parse_expr_for(None, this.prev_token.span) } - err - }) - } else if self.check(&token::OpenDelim(Delimiter::Bracket)) { - self.parse_expr_array_or_repeat(Delimiter::Bracket) - } else if self.is_builtin() { - self.parse_expr_builtin() - } else if self.check_path() { - self.parse_expr_path_start() - } else if self.check_keyword(kw::Move) - || self.check_keyword(kw::Static) - || self.check_const_closure() - { - self.parse_expr_closure() - } else if self.eat_keyword(kw::If) { - self.parse_expr_if() - } else if self.check_keyword(kw::For) { - if self.choose_generics_over_qpath(1) { - self.parse_expr_closure() - } else { - assert!(self.eat_keyword(kw::For)); - self.parse_expr_for(None, self.prev_token.span) - } - } else if self.eat_keyword(kw::While) { - self.parse_expr_while(None, self.prev_token.span) - } else if let Some(label) = self.eat_label() { - self.parse_expr_labeled(label, true) - } else if self.eat_keyword(kw::Loop) { - let sp = self.prev_token.span; - self.parse_expr_loop(None, self.prev_token.span).map_err(|mut err| { - err.span_label(sp, "while parsing this `loop` expression"); - err - }) - } else if self.eat_keyword(kw::Match) { - let match_sp = self.prev_token.span; - self.parse_expr_match().map_err(|mut err| { - err.span_label(match_sp, "while parsing this `match` expression"); - err - }) - } else if self.eat_keyword(kw::Unsafe) { - let sp = self.prev_token.span; - self.parse_expr_block(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err( - |mut err| { - err.span_label(sp, "while parsing this `unsafe` expression"); + } else if this.eat_keyword(kw::While) { + this.parse_expr_while(None, this.prev_token.span) + } else if let Some(label) = this.eat_label() { + this.parse_expr_labeled(label, true) + } else if this.eat_keyword(kw::Loop) { + let sp = this.prev_token.span; + this.parse_expr_loop(None, this.prev_token.span).map_err(|mut err| { + err.span_label(sp, "while parsing this `loop` expression"); err - }, - ) - } else if self.check_inline_const(0) { - self.parse_const_block(lo.to(self.token.span), false) - } else if self.may_recover() && self.is_do_catch_block() { - self.recover_do_catch() - } else if self.is_try_block() { - self.expect_keyword(kw::Try)?; - self.parse_try_block(lo) - } else if self.eat_keyword(kw::Return) { - self.parse_expr_return() - } else if self.eat_keyword(kw::Continue) { - self.parse_expr_continue(lo) - } else if self.eat_keyword(kw::Break) { - self.parse_expr_break() - } else if self.eat_keyword(kw::Yield) { - self.parse_expr_yield() - } else if self.is_do_yeet() { - self.parse_expr_yeet() - } else if self.eat_keyword(kw::Become) { - self.parse_expr_become() - } else if self.check_keyword(kw::Let) { - self.parse_expr_let() - } else if self.eat_keyword(kw::Underscore) { - Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore)) - } else if self.token.uninterpolated_span().at_least_rust_2018() { - // `Span:.at_least_rust_2018()` is somewhat expensive; don't get it repeatedly. - if self.check_keyword(kw::Async) { - if self.is_async_block() { - // Check for `async {` and `async move {`. - self.parse_async_block() + }) + } else if this.eat_keyword(kw::Match) { + let match_sp = this.prev_token.span; + this.parse_expr_match().map_err(|mut err| { + err.span_label(match_sp, "while parsing this `match` expression"); + err + }) + } else if this.eat_keyword(kw::Unsafe) { + let sp = this.prev_token.span; + this.parse_expr_block(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err( + |mut err| { + err.span_label(sp, "while parsing this `unsafe` expression"); + err + }, + ) + } else if this.check_inline_const(0) { + this.parse_const_block(lo.to(this.token.span), false) + } else if this.may_recover() && this.is_do_catch_block() { + this.recover_do_catch() + } else if this.is_try_block() { + this.expect_keyword(kw::Try)?; + this.parse_try_block(lo) + } else if this.eat_keyword(kw::Return) { + this.parse_expr_return() + } else if this.eat_keyword(kw::Continue) { + this.parse_expr_continue(lo) + } else if this.eat_keyword(kw::Break) { + this.parse_expr_break() + } else if this.eat_keyword(kw::Yield) { + this.parse_expr_yield() + } else if this.is_do_yeet() { + this.parse_expr_yeet() + } else if this.eat_keyword(kw::Become) { + this.parse_expr_become() + } else if this.check_keyword(kw::Let) { + this.parse_expr_let(restrictions) + } else if this.eat_keyword(kw::Underscore) { + Ok(this.mk_expr(this.prev_token.span, ExprKind::Underscore)) + } else if this.token.uninterpolated_span().at_least_rust_2018() { + // `Span:.at_least_rust_2018()` is somewhat expensive; don't get it repeatedly. + if this.check_keyword(kw::Async) { + if this.is_async_block() { + // Check for `async {` and `async move {`. + this.parse_async_block() + } else { + this.parse_expr_closure() + } + } else if this.eat_keyword(kw::Await) { + this.recover_incorrect_await_syntax(lo, this.prev_token.span) } else { - self.parse_expr_closure() + this.parse_expr_lit() } - } else if self.eat_keyword(kw::Await) { - self.recover_incorrect_await_syntax(lo, self.prev_token.span) } else { - self.parse_expr_lit() + this.parse_expr_lit() } - } else { - self.parse_expr_lit() - } + }) } fn parse_expr_lit(&mut self) -> PResult<'a, P<Expr>> { @@ -1462,13 +1468,13 @@ impl<'a> Parser<'a> { } } - fn parse_expr_tuple_parens(&mut self) -> PResult<'a, P<Expr>> { + fn parse_expr_tuple_parens(&mut self, restrictions: Restrictions) -> PResult<'a, P<Expr>> { let lo = self.token.span; self.expect(&token::OpenDelim(Delimiter::Parenthesis))?; let (es, trailing_comma) = match self.parse_seq_to_end( &token::CloseDelim(Delimiter::Parenthesis), SeqSep::trailing_allowed(token::Comma), - |p| p.parse_expr_catch_underscore(), + |p| p.parse_expr_catch_underscore(restrictions.intersection(Restrictions::ALLOW_LET)), ) { Ok(x) => x, Err(err) => { @@ -2231,7 +2237,8 @@ impl<'a> Parser<'a> { let decl_hi = self.prev_token.span; let mut body = match fn_decl.output { FnRetTy::Default(_) => { - let restrictions = self.restrictions - Restrictions::STMT_EXPR; + let restrictions = + self.restrictions - Restrictions::STMT_EXPR - Restrictions::ALLOW_LET; self.parse_expr_res(restrictions, None)? } _ => { @@ -2436,10 +2443,12 @@ impl<'a> Parser<'a> { /// Parses the condition of a `if` or `while` expression. fn parse_expr_cond(&mut self) -> PResult<'a, P<Expr>> { - let cond = + let mut cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?; - if let ExprKind::Let(..) = cond.kind { + CondChecker { parser: self, forbid_let_reason: None }.visit_expr(&mut cond); + + if let ExprKind::Let(_, _, _, None) = cond.kind { // Remove the last feature gating of a `let` expression since it's stable. self.sess.gated_spans.ungate_last(sym::let_chains, cond.span); } @@ -2448,18 +2457,15 @@ impl<'a> Parser<'a> { } /// Parses a `let $pat = $expr` pseudo-expression. - fn parse_expr_let(&mut self) -> PResult<'a, P<Expr>> { - // This is a *approximate* heuristic that detects if `let` chains are - // being parsed in the right position. It's approximate because it - // doesn't deny all invalid `let` expressions, just completely wrong usages. - let not_in_chain = !matches!( - self.prev_token.kind, - TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _) - ); - if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain { - self.sess.emit_err(errors::ExpectedExpressionFoundLet { span: self.token.span }); - } - + fn parse_expr_let(&mut self, restrictions: Restrictions) -> PResult<'a, P<Expr>> { + let is_recovered = if !restrictions.contains(Restrictions::ALLOW_LET) { + Some(self.sess.emit_err(errors::ExpectedExpressionFoundLet { + span: self.token.span, + reason: ForbiddenLetReason::OtherForbidden, + })) + } else { + None + }; self.bump(); // Eat `let` token let lo = self.prev_token.span; let pat = self.parse_pat_allow_top_alt( @@ -2477,12 +2483,9 @@ impl<'a> Parser<'a> { } else { self.expect(&token::Eq)?; } - let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| { - this.parse_expr_assoc_with(1 + prec_let_scrutinee_needs_par(), None.into()) - })?; + let expr = self.parse_expr_assoc_with(1 + prec_let_scrutinee_needs_par(), None.into())?; let span = lo.to(expr.span); - self.sess.gated_spans.gate(sym::let_chains, span); - Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span))) + Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span, is_recovered))) } /// Parses an `else { ... }` expression (`else` token already eaten). @@ -2831,7 +2834,10 @@ impl<'a> Parser<'a> { )?; let guard = if this.eat_keyword(kw::If) { let if_span = this.prev_token.span; - let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?; + let mut cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?; + + CondChecker { parser: this, forbid_let_reason: None }.visit_expr(&mut cond); + let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond); if has_let_expr { if does_not_have_bin_op { @@ -3416,3 +3422,130 @@ impl<'a> Parser<'a> { }) } } + +/// Used to forbid `let` expressions in certain syntactic locations. +#[derive(Clone, Copy, Subdiagnostic)] +pub(crate) enum ForbiddenLetReason { + /// `let` is not valid and the source environment is not important + OtherForbidden, + /// A let chain with the `||` operator + #[note(parse_not_supported_or)] + NotSupportedOr(#[primary_span] Span), + /// A let chain with invalid parentheses + /// + /// For example, `let 1 = 1 && (expr && expr)` is allowed + /// but `(let 1 = 1 && (let 1 = 1 && (let 1 = 1))) && let a = 1` is not + #[note(parse_not_supported_parentheses)] + NotSupportedParentheses(#[primary_span] Span), +} + +/// Visitor to check for invalid/unstable use of `ExprKind::Let` that can't +/// easily be caught in parsing. For example: +/// +/// ```rust,ignore (example) +/// // Only know that the let isn't allowed once the `||` token is reached +/// if let Some(x) = y || true {} +/// // Only know that the let isn't allowed once the second `=` token is reached. +/// if let Some(x) = y && z = 1 {} +/// ``` +struct CondChecker<'a> { + parser: &'a Parser<'a>, + forbid_let_reason: Option<ForbiddenLetReason>, +} + +impl MutVisitor for CondChecker<'_> { + fn visit_expr(&mut self, e: &mut P<Expr>) { + use ForbiddenLetReason::*; + + let span = e.span; + match e.kind { + ExprKind::Let(_, _, _, ref mut is_recovered @ None) => { + if let Some(reason) = self.forbid_let_reason { + *is_recovered = Some( + self.parser + .sess + .emit_err(errors::ExpectedExpressionFoundLet { span, reason }), + ); + } else { + self.parser.sess.gated_spans.gate(sym::let_chains, span); + } + } + ExprKind::Binary(Spanned { node: BinOpKind::And, .. }, _, _) => { + noop_visit_expr(e, self); + } + ExprKind::Binary(Spanned { node: BinOpKind::Or, span: or_span }, _, _) + if let None | Some(NotSupportedOr(_)) = self.forbid_let_reason => + { + let forbid_let_reason = self.forbid_let_reason; + self.forbid_let_reason = Some(NotSupportedOr(or_span)); + noop_visit_expr(e, self); + self.forbid_let_reason = forbid_let_reason; + } + ExprKind::Paren(ref inner) + if let None | Some(NotSupportedParentheses(_)) = self.forbid_let_reason => + { + let forbid_let_reason = self.forbid_let_reason; + self.forbid_let_reason = Some(NotSupportedParentheses(inner.span)); + noop_visit_expr(e, self); + self.forbid_let_reason = forbid_let_reason; + } + ExprKind::Unary(_, _) + | ExprKind::Await(_, _) + | ExprKind::Assign(_, _, _) + | ExprKind::AssignOp(_, _, _) + | ExprKind::Range(_, _, _) + | ExprKind::Try(_) + | ExprKind::AddrOf(_, _, _) + | ExprKind::Binary(_, _, _) + | ExprKind::Field(_, _) + | ExprKind::Index(_, _, _) + | ExprKind::Call(_, _) + | ExprKind::MethodCall(_) + | ExprKind::Tup(_) + | ExprKind::Paren(_) => { + let forbid_let_reason = self.forbid_let_reason; + self.forbid_let_reason = Some(OtherForbidden); + noop_visit_expr(e, self); + self.forbid_let_reason = forbid_let_reason; + } + ExprKind::Cast(ref mut op, _) + | ExprKind::Type(ref mut op, _) => { + let forbid_let_reason = self.forbid_let_reason; + self.forbid_let_reason = Some(OtherForbidden); + self.visit_expr(op); + self.forbid_let_reason = forbid_let_reason; + } + ExprKind::Let(_, _, _, Some(_)) + | ExprKind::Array(_) + | ExprKind::ConstBlock(_) + | ExprKind::Lit(_) + | ExprKind::If(_, _, _) + | ExprKind::While(_, _, _) + | ExprKind::ForLoop(_, _, _, _) + | ExprKind::Loop(_, _, _) + | ExprKind::Match(_, _) + | ExprKind::Closure(_) + | ExprKind::Block(_, _) + | ExprKind::Async(_, _) + | ExprKind::TryBlock(_) + | ExprKind::Underscore + | ExprKind::Path(_, _) + | ExprKind::Break(_, _) + | ExprKind::Continue(_) + | ExprKind::Ret(_) + | ExprKind::InlineAsm(_) + | ExprKind::OffsetOf(_, _) + | ExprKind::MacCall(_) + | ExprKind::Struct(_) + | ExprKind::Repeat(_, _) + | ExprKind::Yield(_) + | ExprKind::Yeet(_) + | ExprKind::Become(_) + | ExprKind::IncludedBytes(_) + | ExprKind::FormatArgs(_) + | ExprKind::Err => { + // These would forbid any let expressions they contain already. + } + } + } +} |