From 667b15bb0ebb36683a2de31cff68ad2b5b0d3f57 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Thu, 27 Oct 2022 14:43:15 +0800
Subject: fix #103587, Recover from common if let syntax mistakes/typos

---
 compiler/rustc_parse/src/errors.rs      |  9 +++++++++
 compiler/rustc_parse/src/parser/expr.rs | 16 ++++++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

(limited to 'compiler/rustc_parse/src')

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 0924c853715..89d5fe3d9da 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -420,6 +420,15 @@ pub(crate) struct ExpectedExpressionFoundLet {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parser_expect_eq_instead_of_eqeq)]
+pub(crate) struct ExpectedEqForLetExpr {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion_verbose(applicability = "maybe-incorrect", code = "=")]
+    pub sugg_span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(parser_expected_else_block)]
 pub(crate) struct ExpectedElseBlock {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 4a1162b9599..565371668a8 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -9,9 +9,9 @@ use crate::errors::{
     ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncMoveOrderIncorrect,
     BinaryFloatLiteralNotSupported, BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct,
     ComparisonInterpretedAsGeneric, ComparisonOrShiftInterpretedAsGenericSugg,
-    DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedExpressionFoundLet,
-    FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart, FoundExprWouldBeStmt,
-    HexadecimalFloatLiteralNotSupported, IfExpressionMissingCondition,
+    DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedEqForLetExpr,
+    ExpectedExpressionFoundLet, FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart,
+    FoundExprWouldBeStmt, HexadecimalFloatLiteralNotSupported, IfExpressionMissingCondition,
     IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub, IntLiteralTooLarge,
     InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
     InvalidFloatLiteralSuffix, InvalidFloatLiteralWidth, InvalidIntLiteralWidth,
@@ -2334,7 +2334,15 @@ impl<'a> Parser<'a> {
             RecoverColon::Yes,
             CommaRecoveryMode::LikelyTuple,
         )?;
-        self.expect(&token::Eq)?;
+        if self.token == token::EqEq {
+            self.sess.emit_err(ExpectedEqForLetExpr {
+                span: self.token.span,
+                sugg_span: self.token.span,
+            });
+            self.bump();
+        } else {
+            self.expect(&token::Eq)?;
+        }
         let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
             this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
         })?;
-- 
cgit 1.4.1-3-g733a5