[CodeCompletion] Don't emit member type construction for the same type

in unresolved member completion. e.g.

  struct Node {
    typealias Child = Node
    init(children: [Child]) {}
  }
  let node: Node = .#^COMPLETE^#

This used to emit `.init(children:)` and `.Child(children:)`.

Author: rintaro

lib/IDE/CodeCompletion.cpp

@@ -3825,7 +3825,12 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
       // convertible to the contextual type.
       if (auto CD = dyn_cast<TypeDecl>(VD)) {
         declTy = declTy->getMetatypeInstanceType();
-        return declTy->isEqual(T) || swift::isConvertibleTo(declTy, T, *DC);
+
+        // Emit construction for the same type via typealias doesn't make sense
+        // because we are emitting all `.init()`s.
+        if (declTy->isEqual(T))
+          return false;
+        return swift::isConvertibleTo(declTy, T, *DC);
       }
 
       // Only static member can be referenced.

test/IDE/complete_unresolved_members.swift

@@ -443,12 +443,12 @@ struct AnotherTy: MyProtocol {}
 func testSubType() {
   var _: BaseClass = .#^SUBTYPE_1^#
 }
-// SUBTYPE_1: Begin completions, 4 items
+// SUBTYPE_1: Begin completions, 3 items
 // SUBTYPE_1-NOT: init(failable:
+// SUBTYPE_1-NOT: Concrete1(
 // SUBTYPE_1-DAG: Decl[Constructor]/CurrNominal/TypeRelation[Identical]: init()[#BaseClass#];
 // SUBTYPE_1-DAG: Decl[Constructor]/CurrNominal/TypeRelation[Convertible]: SubClass()[#BaseClass.SubClass#];
 // SUBTYPE_1-DAG: Decl[StaticVar]/CurrNominal/TypeRelation[Convertible]: subInstance[#BaseClass.SubClass#];
-// SUBTYPE_1-DAG: Decl[Constructor]/Super/TypeRelation[Identical]: Concrete1()[#BaseClass#];
 // SUBTYPE_1: End completions
 
 func testMemberTypealias() {