Fix SR-642 Code completion does not instantiate concrete element type of optional Set

Author: ahoppen

lib/IDE/CodeCompletion.cpp

@@ -1708,9 +1708,10 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
       Type ContextTy = VD->getDeclContext()->getDeclaredTypeOfContext();
       if (ContextTy) {
         Type MaybeNominalType = ExprType->getRValueInstanceType();
-        if (ContextTy->getAnyNominal() == MaybeNominalType->getAnyNominal() &&
+        if (ContextTy->lookThroughAllAnyOptionalTypes()->getAnyNominal() ==
+            MaybeNominalType->lookThroughAllAnyOptionalTypes()->getAnyNominal() &&
             !isBoringBoundGenericType(MaybeNominalType)) {
-          if (Type T = MaybeNominalType->getTypeOfMember(
+          if (Type T = MaybeNominalType->lookThroughAllAnyOptionalTypes()->getTypeOfMember(
               CurrDeclContext->getParentModule(), VD, TypeResolver.get()))
             return TransformerPt ? T.transform(TransformerPt->getTransformerFunc()) :
                                    T;

test/IDE/complete_generic_optional.swift

@@ -0,0 +1,16 @@
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=FOO_OPTIONAL_1 | FileCheck %s -check-prefix=FOO_OPTIONAL_1
+
+struct Bar {
+}
+
+struct Foo<T> {
+  func myFunction(foobar: T) {
+  }
+}
+
+// SR-642 Code completion does not instantiate generic arguments of a type wrapped in an optional
+let x: Foo<Bar>? = Foo<Bar>()
+x.#^FOO_OPTIONAL_1^#
+// FOO_OPTIONAL_1: Begin completions, 4 items
+// FOO_OPTIONAL_1-DAG: Decl[InstanceMethod]/CurrNominal/Erase[1]: ?.myFunction({#(foobar): Bar#})[#Void#]; name=myFunction(foobar: Bar)
+// FOO_OPTIONAL_1: End completions