[fixits] Don't fixit-remove generic arguments on ModuleType

Seeing Module<Args> is more likely to indicate some catastrophic
failure, for instance a missing type with the same name as the module,
than that we should remove the generic arguments.

rdar://problem/26639477

Author: benlangmuir

lib/Sema/TypeCheckType.cpp

@@ -417,9 +417,14 @@ Type TypeChecker::applyGenericArguments(Type type, SourceLoc loc,
 
   auto unbound = type->getAs<UnboundGenericType>();
   if (!unbound) {
-    if (!type->is<ErrorType>())
-      diagnose(loc, diag::not_a_generic_type, type)
-          .fixItRemove(generic->getAngleBrackets());
+    if (!type->is<ErrorType>()) {
+      auto diag = diagnose(loc, diag::not_a_generic_type, type);
+
+      // Don't add fixit on module type; that isn't the right type regardless
+      // of whether it had generic arguments.
+      if (!type->is<ModuleType>())
+        diag.fixItRemove(generic->getAngleBrackets());
+    }
     generic->setInvalid();
     return type;
   }

test/FixCode/Inputs/module.modulemap

@@ -0,0 +1 @@
+module Empty {}

test/FixCode/fixits-apply.swift

@@ -1,4 +1,4 @@
-// RUN: not %swift -parse -target %target-triple %s -emit-fixits-path %t.remap
+// RUN: not %swift -parse -target %target-triple %s -emit-fixits-path %t.remap -I %S/Inputs
 // RUN: c-arcmt-test %t.remap | arcmt-test -verify-transformed-files %s.result
 
 class Base {}
@@ -156,3 +156,6 @@ func evilCommas(s: String) {
   _ = true ? s[s.startIndex..<<#editorplaceholder#>] : ""
   _ = [s.startIndex..<<#editorplaceholder#>]
 }
+
+import Empty
+func testGenericSig(x: Empty<Int>) -> Empty<String> {}

test/FixCode/fixits-apply.swift.result

@@ -1,4 +1,4 @@
-// RUN: not %swift -parse -target %target-triple %s -emit-fixits-path %t.remap
+// RUN: not %swift -parse -target %target-triple %s -emit-fixits-path %t.remap -I %S/Inputs
 // RUN: c-arcmt-test %t.remap | arcmt-test -verify-transformed-files %s.result
 
 class Base {}
@@ -159,3 +159,6 @@ func evilCommas(s: String) {
   _ = true ? s[s.startIndex..<<#editorplaceholder#>] : ""
   _ = [s.startIndex..<<#editorplaceholder#>]
 }
+
+import Empty
+func testGenericSig(x: Empty<Int>) -> Empty<String> {}