[Modules] Fix a crash-on-invalid with overloaded functions

Do not add an overload if the function doesn't have a prototype; this
can happen if, for instance, a misplaced/malformed call site is
considered like a declaration for recovery purposes.

rdar://problem/31306325

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@301453 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaOverload.cpp

@@ -11426,6 +11426,10 @@ static void AddOverloadedCallCandidate(Sema &S,
       assert(!KnownValid && "Explicit template arguments?");
       return;
     }
+    // Prevent ill-formed function decls to be added as overload candidates.
+    if (!dyn_cast<FunctionProtoType>(Func->getType()->getAs<FunctionType>()))
+      return;
+
     S.AddOverloadCandidate(Func, FoundDecl, Args, CandidateSet,
                            /*SuppressUsedConversions=*/false,
                            PartialOverloading);

test/Modules/Inputs/malformed-overload/X.h

@@ -0,0 +1,2 @@
+@class NSString;
+extern void NSLog(NSString *format, ...) __attribute__((format(__NSString__, 1, 2))) __attribute__((not_tail_called));

test/Modules/Inputs/malformed-overload/module.modulemap

@@ -0,0 +1,4 @@
+module X {
+  header "X.h"
+  export *
+}

test/Modules/malformed-overload.m

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -I%S/Inputs/malformed-overload -fmodules -fimplicit-module-maps -fmodules-cache-path=tmp -verify %s
+NSLog(@"%@", path); // expected-error {{expected parameter declarator}} expected-error {{expected ')'}} expected-warning {{type specifier missing}} expected-warning {{incompatible redeclaration}} expected-note {{to match this '('}} expected-note {{'NSLog' is a builtin with type}}
+#import "X.h"
+
+@class NSString;
+void f(NSString *a) {
+ NSLog(@"***** failed to get URL for %@", a);
+}