[PATCH] D13664: [Fix] Don't emit multiple diagnostics for the same error

[George Burgess IV via cfe-commits]

george.burgess.iv created this revision.
george.burgess.iv added a reviewer: rsmith.
george.burgess.iv added a subscriber: cfe-commits.

Given code like the following (stolen from tests):

```
template <typename T1, typename T2> int f(T1 *, const T2 *);
template <typename T1, typename T2> int f(const T1 *, T2 *);
int (*p)(const int *, const int *) = f;
```

Clang will currently emit two "address of overloaded function f is ambiguous" errors for the same assignment (on line 3). 

This patch makes us only emit one.

http://reviews.llvm.org/D13664

Files:
  lib/Sema/SemaOverload.cpp
  test/SemaCXX/addr-of-overloaded-function.cpp

Index: test/SemaCXX/addr-of-overloaded-function.cpp
===================================================================
--- test/SemaCXX/addr-of-overloaded-function.cpp
+++ test/SemaCXX/addr-of-overloaded-function.cpp
@@ -125,13 +125,9 @@
 }
 
 namespace PR8033 {
-  template <typename T1, typename T2> int f(T1 *, const T2 *); // expected-note {{candidate function [with T1 = const int, T2 = int]}} \
-  // expected-note{{candidate function}}
-  template <typename T1, typename T2> int f(const T1 *, T2 *); // expected-note {{candidate function [with T1 = int, T2 = const int]}} \
-  // expected-note{{candidate function}}
-  int (*p)(const int *, const int *) = f; // expected-error{{address of overloaded function 'f' is ambiguous}} \
-  // expected-error{{address of overloaded function 'f' is ambiguous}}
-
+  template <typename T1, typename T2> int f(T1 *, const T2 *); // expected-note {{candidate function [with T1 = const int, T2 = int]}}
+  template <typename T1, typename T2> int f(const T1 *, T2 *); // expected-note {{candidate function [with T1 = int, T2 = const int]}}
+  int (*p)(const int *, const int *) = f; // expected-error{{address of overloaded function 'f' is ambiguous}}
 }
 
 namespace PR8196 {
Index: lib/Sema/SemaOverload.cpp
===================================================================
--- lib/Sema/SemaOverload.cpp
+++ lib/Sema/SemaOverload.cpp
@@ -9911,6 +9911,7 @@
   bool TargetTypeIsNonStaticMemberFunction;
   bool FoundNonTemplateFunction;
   bool StaticMemberFunctionFromBoundPointer;
+  bool HasComplained;
 
   OverloadExpr::FindResult OvlExprInfo; 
   OverloadExpr *OvlExpr;
@@ -9927,6 +9928,7 @@
             !!TargetType->getAs<MemberPointerType>()),
         FoundNonTemplateFunction(false),
         StaticMemberFunctionFromBoundPointer(false),
+        HasComplained(false),
         OvlExprInfo(OverloadExpr::find(SourceExpr)),
         OvlExpr(OvlExprInfo.Expression),
         FailedCandidates(OvlExpr->getNameLoc()) {
@@ -9977,7 +9979,9 @@
         Matches.size() > 1)
       EliminateSuboptimalCudaMatches();
   }
-  
+
+  bool hasComplained() const { return HasComplained; }
+
 private:
   bool isTargetTypeAFunction() const {
     return TargetFunctionType->isFunctionType();
@@ -10056,9 +10060,12 @@
       // If any candidate has a placeholder return type, trigger its deduction
       // now.
       if (S.getLangOpts().CPlusPlus14 &&
-          FunDecl->getReturnType()->isUndeducedType() &&
-          S.DeduceReturnType(FunDecl, SourceExpr->getLocStart(), Complain))
-        return false;
+          FunDecl->getReturnType()->isUndeducedType()) {
+        if (S.DeduceReturnType(FunDecl, SourceExpr->getLocStart(), Complain)) {
+          HasComplained |= Complain;
+          return false;
+        }
+      }
 
       QualType ResultTy;
       if (Context.hasSameUnqualifiedType(TargetFunctionType, 
@@ -10140,7 +10147,8 @@
       Matches[0].first = Matches[Result - MatchesCopy.begin()].first;
       Matches[0].second = cast<FunctionDecl>(*Result);
       Matches.resize(1);
-    }
+    } else
+      HasComplained |= Complain;
   }
 
   void EliminateAllTemplateMatches() {
@@ -10261,13 +10269,14 @@
                                      Complain);
   int NumMatches = Resolver.getNumMatches();
   FunctionDecl *Fn = nullptr;
-  if (NumMatches == 0 && Complain) {
+  bool ShouldComplain = Complain && !Resolver.hasComplained();
+  if (NumMatches == 0 && ShouldComplain) {
     if (Resolver.IsInvalidFormOfPointerToMemberFunction())
       Resolver.ComplainIsInvalidFormOfPointerToMemberFunction();
     else
       Resolver.ComplainNoMatchesFound();
   }
-  else if (NumMatches > 1 && Complain)
+  else if (NumMatches > 1 && ShouldComplain)
     Resolver.ComplainMultipleMatchesFound();
   else if (NumMatches == 1) {
     Fn = Resolver.getMatchingFunctionDecl();


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