From d80516ddef8d4010f79cad378d8716676aa74ebd Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Wed, 8 May 2019 05:49:42 +0000
Subject: [PATCH] [Sema] Correct typos in return statements so the return types
 of 'auto' functions are always deduced.

Summary:
e.g.
  auto foo() {
    return no_such_thing; // Return value is a TypoExpr
  }
  using T = decltype(foo()); // Uh-oh, undeduced auto.

Reviewers: rsmith

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61649

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360224 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaStmt.cpp                  |  8 +++++++-
 test/SemaCXX/typo-correction-crash.cpp | 13 ++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index fe0cf74496..c7fb565451 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Sema/Ownership.h"
 #include "clang/Sema/SemaInternal.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
@@ -3503,7 +3504,12 @@ bool Sema::DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD,
 StmtResult
 Sema::ActOnReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
                       Scope *CurScope) {
-  StmtResult R = BuildReturnStmt(ReturnLoc, RetValExp);
+  // Correct typos, in case the containing function returns 'auto' and
+  // RetValExp should determine the deduced type.
+  ExprResult RetVal = CorrectDelayedTyposInExpr(RetValExp);
+  if (RetVal.isInvalid())
+    return StmtError();
+  StmtResult R = BuildReturnStmt(ReturnLoc, RetVal.get());
   if (R.isInvalid() || ExprEvalContexts.back().Context ==
                            ExpressionEvaluationContext::DiscardedStatement)
     return R;
diff --git a/test/SemaCXX/typo-correction-crash.cpp b/test/SemaCXX/typo-correction-crash.cpp
index b7b9c73a0c..fce10800f2 100644
--- a/test/SemaCXX/typo-correction-crash.cpp
+++ b/test/SemaCXX/typo-correction-crash.cpp
@@ -4,12 +4,23 @@ auto check1() {
   return s; // expected-error {{use of undeclared identifier 's'}}
 }
 
-int test = 11; // expected-note {{'test' declared here}}
+int test = 11; // expected-note 2 {{'test' declared here}}
 auto check2() {
   return "s";
   return tes; // expected-error {{use of undeclared identifier 'tes'; did you mean 'test'?}}
+              // expected-error@-1 {{deduced as 'int' here but deduced as 'const char *' in earlier}}
 }
 
+template <class A, class B> struct is_same { static constexpr bool value = false; };
+template <class A> struct is_same<A,A> { static constexpr bool value = true; };
+
+auto L1 = [] { return s; }; // expected-error {{use of undeclared identifier 's'}}
+using T1 = decltype(L1());
+static_assert(is_same<T1, void>::value, "Return statement should be discarded");
+auto L2 = [] { return tes; }; // expected-error {{use of undeclared identifier 'tes'; did you mean 'test'?}}
+using T2 = decltype(L2());
+static_assert(is_same<T2, int>::value, "Return statement was corrected");
+
 namespace BarNamespace {
 namespace NestedNamespace { // expected-note {{'BarNamespace::NestedNamespace' declared here}}
 typedef int type;
-- 
2.40.0