[CodeComplete] Complete parameter labels in self.init call

The `init` of `self.init` needs to be looked up on the Metatype of `self`, not on the type of `self` itself. We were already doing a similar special-casing for `super.init`, which I extened to also cover `self.init`.

Resolves rdar://36521732

Author: ahoppen

lib/IDE/ExprContextAnalysis.cpp

@@ -551,10 +551,20 @@ static void collectPossibleCalleesByQualifiedLookup(
   }
   baseTy = baseTy->getWithoutSpecifierType();
 
-  // Use metatype for lookup 'super.init' if it's inside constructors.
-  if (isa<SuperRefExpr>(baseExpr) && isa<ConstructorDecl>(DC) &&
-      name == DeclNameRef::createConstructor())
-    baseTy = MetatypeType::get(baseTy);
+  // Use metatype for lookup 'super.init' and 'self.init' if it's inside
+  // constructors.
+  if (name == DeclNameRef::createConstructor() && isa<ConstructorDecl>(DC)) {
+    bool isSuperCall = isa<SuperRefExpr>(baseExpr);
+    bool isSelfCall = false;
+    if (auto declRef = dyn_cast<DeclRefExpr>(baseExpr)) {
+      if (declRef->getDecl()->getName() == DC.getASTContext().Id_self) {
+        isSelfCall = true;
+      }
+    }
+    if (isSuperCall || isSelfCall) {
+      baseTy = MetatypeType::get(baseTy);
+    }
+  }
 
   collectPossibleCalleesByQualifiedLookup(DC, baseTy, name, candidates);
 

test/IDE/complete_call_arg.swift

@@ -114,6 +114,8 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=VARIADIC_2 | %FileCheck %s -check-prefix=VARIADIC_2
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=VARIADIC_3 | %FileCheck %s -check-prefix=VARIADIC_2
 
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=LABEL_IN_SELF_DOT_INIT | %FileCheck %s -check-prefix=LABEL_IN_SELF_DOT_INIT
+
 var i1 = 1
 var i2 = 2
 var oi1 : Int?
@@ -909,3 +911,15 @@ func testVariadic(_ arg: Any..., option1: Int = 0, option2: String = 1) {
     testVariadic(1, 2, #^VARIADIC_3^#)
 // Same as VARIADIC_2.
 }
+
+func testLabelsInSelfDotInit() {
+  class Foo {
+    init(a: Int, b: Int) {}
+    convenience init() {
+      self.init(a: 1, #^LABEL_IN_SELF_DOT_INIT^#)
+// LABEL_IN_SELF_DOT_INIT: Begin completions, 1 item
+// LABEL_IN_SELF_DOT_INIT-DAG: Pattern/ExprSpecific:               {#b: Int#}[#Int#]
+// LABEL_IN_SELF_DOT_INIT: End completions
+    }
+  }
+}