Merge commit '39683d8eb7a32a74bea96ecbf1e87675d3338506' into sync_cg_gcc-2022-03-26

[rust.git] / compiler / rustc_parse / src / parser / expr.rs

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index ef006d5fcda8cf5a0fe65caa0413eacc644dbd8f..148e0a24ec304f5b38793a7f2a07224d21dd3979 100644 (file)
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1,9 +1,10 @@
+use super::diagnostics::SnapshotParser;
 use super::pat::{CommaRecoveryMode, RecoverColon, RecoverComma, PARAM_EXPECTED};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{
-    AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions, TokenType,
+    AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
+    SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
 };
-use super::{SemiColonMode, SeqSep, TokenExpectType, TrailingToken};
 use crate::maybe_recover_from_interpolated_ty_qpath;
 
 use ast::token::DelimToken;
@@ -799,11 +800,17 @@ fn parse_and_disallow_postfix_after_cast(
         &mut self,
         cast_expr: P<Expr>,
     ) -> PResult<'a, P<Expr>> {
+        let span = cast_expr.span;
+        let maybe_ascription_span = if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
+            Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi()))
+        } else {
+            None
+        };
+
         // Save the memory location of expr before parsing any following postfix operators.
         // This will be compared with the memory location of the output expression.
         // If they different we can assume we parsed another expression because the existing expression is not reallocated.
         let addr_before = &*cast_expr as *const _ as usize;
-        let span = cast_expr.span;
         let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
         let changed = addr_before != &*with_postfix as *const _ as usize;
 
@@ -824,11 +831,8 @@ fn parse_and_disallow_postfix_after_cast(
                 }
             );
             let mut err = self.struct_span_err(span, &msg);
-            // If type ascription is "likely an error", the user will already be getting a useful
-            // help message, and doesn't need a second.
-            if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
-                self.maybe_annotate_with_ascription(&mut err, false);
-            } else {
+
+            let suggest_parens = |err: &mut DiagnosticBuilder<'_, _>| {
                 let suggestions = vec![
                     (span.shrink_to_lo(), "(".to_string()),
                     (span.shrink_to_hi(), ")".to_string()),
@@ -838,6 +842,32 @@ fn parse_and_disallow_postfix_after_cast(
                     suggestions,
                     Applicability::MachineApplicable,
                 );
+            };
+
+            // If type ascription is "likely an error", the user will already be getting a useful
+            // help message, and doesn't need a second.
+            if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
+                self.maybe_annotate_with_ascription(&mut err, false);
+            } else if let Some(ascription_span) = maybe_ascription_span {
+                let is_nightly = self.sess.unstable_features.is_nightly_build();
+                if is_nightly {
+                    suggest_parens(&mut err);
+                }
+                err.span_suggestion(
+                    ascription_span,
+                    &format!(
+                        "{}remove the type ascription",
+                        if is_nightly { "alternatively, " } else { "" }
+                    ),
+                    String::new(),
+                    if is_nightly {
+                        Applicability::MaybeIncorrect
+                    } else {
+                        Applicability::MachineApplicable
+                    },
+                );
+            } else {
+                suggest_parens(&mut err);
             }
             err.emit();
         };
@@ -1105,7 +1135,7 @@ fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
         let snapshot = if self.token.kind == token::OpenDelim(token::Paren)
             && self.look_ahead_type_ascription_as_field()
         {
-            Some((self.clone(), fun.kind.clone()))
+            Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
         } else {
             None
         };
@@ -1130,7 +1160,7 @@ fn maybe_recover_struct_lit_bad_delims(
         lo: Span,
         open_paren: Span,
         seq: &mut PResult<'a, P<Expr>>,
-        snapshot: Option<(Self, ExprKind)>,
+        snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
     ) -> Option<P<Expr>> {
         match (seq.as_mut(), snapshot) {
             (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
@@ -1140,7 +1170,7 @@ fn maybe_recover_struct_lit_bad_delims(
                     Ok((fields, ..)) if snapshot.eat(&token::CloseDelim(token::Paren)) => {
                         // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
                         // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
-                        *self = snapshot;
+                        self.restore_snapshot(snapshot);
                         let close_paren = self.prev_token.span;
                         let span = lo.to(self.prev_token.span);
                         if !fields.is_empty() {