Reject member lookups that require bridging metatypes

We can only coerce metatypes covariantly but bridging
always requires an unrelated metatype cast.  When
performing member lookup, especially unqualified member
lookup, disregard static members from bridged types entirely.

See SR-5670 and rdar://problem/33830526

Author: CodaFi

lib/Sema/CSSimplify.cpp

@@ -3263,7 +3263,7 @@ performMemberLookup(ConstraintKind constraintKind, DeclName memberName,
 
   // If the instance type is a bridged to an Objective-C type, perform
   // a lookup into that Objective-C type.
-  if (bridgedType) {
+  if (bridgedType && !isMetatype) {
     LookupResult &bridgedLookup = lookupMember(bridgedClass, memberName);
     ModuleDecl *foundationModule = nullptr;
     for (auto result : bridgedLookup) {

test/Constraints/Inputs/invalid_metatype_bridging_header.h

@@ -0,0 +1,7 @@
+@import Foundation;
+
+// rdar://problem/33830526: Constraint system should not add static methods
+// to the overload search space if it would require bridging unrelated metatypes.
+@interface NSString (Extension)
++ (void) meth;
+@end

test/Constraints/invalid_metatype_bridging_header.swift

@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend -typecheck -import-objc-header %S/Inputs/invalid_metatype_bridging_header.h %s -verify
+
+// REQUIRES: objc_interop
+
+// rdar://problem/33830526: Constraint system should not add static methods
+// to the overload search space if it would require bridging unrelated metatypes.
+class Crasher {
+  static func called(argument: String) {}
+}
+
+Crasher.called(argument: .meth) // expected-error {{type 'String' has no member 'meth'}}
+Crasher.called(argument: String.meth) // expected-error {{type 'String' has no member 'meth'}}