[Serialization] Don't look at extension members when resolving XREFs.

This is mostly a "don't crash" commit, but since member XREFs don't
specify which module they're looking in, they can actually pick up
members from the module currently being compiled...which may not have
a type yet.

rdar://problem/21071045

Swift SVN r30895

lib/Serialization/Deserialization.cpp

@@ -982,6 +982,8 @@ static void filterValues(Type expectedTy, Module *expectedModule,
                                [=](ValueDecl *value) {
     if (isType != isa<TypeDecl>(value))
       return true;
+    if (!value->hasType())
+      return true;
     if (canTy && value->getInterfaceType()->getCanonicalType() != canTy)
       return true;
     // FIXME: Should be able to move a value from an extension in a derived

test/Serialization/Inputs/has_xref.swift

@@ -13,3 +13,9 @@ public protocol ExtraIncrementable {
 }
 
 extension SpecialInt : ExtraIncrementable {}
+
+public protocol DefaultInitializable {
+  init()
+}
+
+extension SpecialInt : DefaultInitializable {}

test/Serialization/Inputs/xref-multi-file-other.swift

@@ -0,0 +1,5 @@
+import has_xref
+
+extension SpecialInt {
+  init(conflict: ()) {}
+}

test/Serialization/xref-multi-file.swift

@@ -0,0 +1,15 @@
+// RUN: rm -rf %t && mkdir %t
+// RUN: %target-swift-frontend -emit-module -o %t %S/Inputs/struct_with_operators.swift
+// RUN: %target-swift-frontend -emit-module -o %t %S/Inputs/alias.swift -module-name has_alias
+// RUN: %target-swift-frontend -emit-module -o %t -I %t %S/Inputs/has_xref.swift
+// RUN: llvm-bcanalyzer %t/has_xref.swiftmodule | FileCheck %s
+// RUN: %target-swift-frontend -emit-silgen -I %t -primary-file %s %S/Inputs/xref-multi-file-other.swift -module-name main > /dev/null
+
+// CHECK-NOT: UnknownCode
+
+import has_xref
+
+func use<T: DefaultInitializable>(_: T) {}
+func test(x: SpecialInt) {
+  use(x)
+}