[Sema] Fix operator lookup to consider local extern declarations.

Summary:
Previously Clang was not considering operator declarations that occur at function scope. This is incorrect according to [over.match.oper]p3
> The set of non-member candidates is the result of the unqualified lookup of operator@ in the context of the expression according to the usual rules for name lookup in unqualified function calls.

This patch changes operator name lookup to consider block scope declarations.
This patch fixes PR27027.




Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D35297

llvm-svn: 309530

clang/lib/Sema/SemaLookup.cpp

@@ -1031,7 +1031,8 @@ struct FindLocalExternScope {
   FindLocalExternScope(LookupResult &R)
       : R(R), OldFindLocalExtern(R.getIdentifierNamespace() &
                                  Decl::IDNS_LocalExtern) {
-    R.setFindLocalExtern(R.getIdentifierNamespace() & Decl::IDNS_Ordinary);
+    R.setFindLocalExtern(R.getIdentifierNamespace() &
+                         (Decl::IDNS_Ordinary | Decl::IDNS_NonMemberOperator));
   }
   void restore() {
     R.setFindLocalExtern(OldFindLocalExtern);

clang/test/SemaCXX/overloaded-operator.cpp

@@ -531,3 +531,22 @@ namespace NoADLForMemberOnlyOperators {
     b3 / 0; // expected-note {{in instantiation of}} expected-error {{invalid operands to}}
   }
 }
+
+
+namespace PR27027 {
+  template <class T> void operator+(T, T) = delete; // expected-note 4 {{candidate}}
+  template <class T> void operator+(T) = delete; // expected-note 4 {{candidate}}
+
+  struct A {} a_global;
+  void f() {
+    A a;
+    +a; // expected-error {{overload resolution selected deleted operator '+'}}
+    a + a; // expected-error {{overload resolution selected deleted operator '+'}}
+    bool operator+(A);
+    extern bool operator+(A, A);
+    +a; // OK
+    a + a;
+  }
+  bool test_global_1 = +a_global; // expected-error {{overload resolution selected deleted operator '+'}}
+  bool test_global_2 = a_global + a_global; // expected-error {{overload resolution selected deleted operator '+'}}
+}