[CSOptimizer] MemberImportVisibility: Don't consider overloads that come from implicit imports

Ignore declarations that come from implicitly imported modules
when `MemberImportVisibility` feature is enabled otherwise
we might end up favoring an overload that would be diagnosed
as unavailable later.

Resolves: rdar://143582881

Author: xedin

lib/Sema/CSOptimizer.cpp

@@ -175,6 +175,18 @@ void forEachDisjunctionChoice(
     if (!decl)
       continue;
 
+    // Ignore declarations that come from implicitly imported modules
+    // when `MemberImportVisibility` feature is enabled otherwise
+    // we might end up favoring an overload that would be diagnosed
+    // as unavailable later.
+    if (cs.getASTContext().LangOpts.hasFeature(
+            Feature::MemberImportVisibility)) {
+      if (auto *useDC = constraint->getOverloadUseDC()) {
+        if (!useDC->isDeclImported(decl))
+          continue;
+      }
+    }
+
     // If disjunction choice is unavailable or disfavored we cannot
     // do anything with it.
     if (decl->getAttrs().hasAttribute<DisfavoredOverloadAttr>() ||

validation-test/Sema/rdar143582881.swift

@@ -0,0 +1,16 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -typecheck %t/Main.swift %t/Other.swift -enable-upcoming-feature MemberImportVisibility
+
+//--- Main.swift
+
+import Foundation
+
+func test() -> CGSize {
+  return CGSize(width: 60, height: 45)
+}
+
+//--- Other.swift
+
+import CoreGraphics