---

yaml
---
r: 349179
b: refs/heads/master-next
c: 9406edc
h: refs/heads/master
i:
  349177: feba36c
  349175: d08625e

Author: xedin

[refs]

@@ -1,6 +1,6 @@
 ---
 refs/heads/master: 3574c513bbc5578dd9346b4ea9ab5995c5927bb5
-refs/heads/master-next: 60bcc9457516cab412b06d9ef907e1ca46bf443e
+refs/heads/master-next: 9406edc017f1be00e5411f3abcaccd7b53b15675
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-b: 66d897bfcf64a82cb9a87f5e663d889189d06d07

branches/master-next/lib/Sema/CSDiagnostics.cpp

@@ -3740,6 +3740,10 @@ bool MissingArgumentsFailure::diagnoseSingleMissingArgument() const {
   if (label.empty()) {
     emitDiagnostic(insertLoc, diag::missing_argument_positional, position + 1)
         .fixItInsert(insertLoc, insertText.str());
+  } else if (isPropertyWrapperInitialization()) {
+    auto *TE = cast<TypeExpr>(fnExpr);
+    emitDiagnostic(TE->getLoc(), diag::property_wrapper_missing_arg_init, label,
+                   resolveType(TE->getInstanceType())->getString());
   } else {
     emitDiagnostic(insertLoc, diag::missing_argument_named, label)
         .fixItInsert(insertLoc, insertText.str());
@@ -3880,6 +3884,23 @@ bool MissingArgumentsFailure::diagnoseInvalidTupleDestructuring() const {
   return true;
 }
 
+bool MissingArgumentsFailure::isPropertyWrapperInitialization() const {
+  auto *call = dyn_cast<CallExpr>(getRawAnchor());
+  if (!(call && call->isImplicit()))
+    return false;
+
+  auto TE = dyn_cast<TypeExpr>(call->getFn());
+  if (!TE)
+    return false;
+
+  auto instanceTy = TE->getInstanceType();
+  if (!instanceTy)
+    return false;
+
+  auto *NTD = resolveType(instanceTy)->getAnyNominal();
+  return NTD && NTD->getAttrs().hasAttribute<PropertyWrapperAttr>();
+}
+
 bool ClosureParamDestructuringFailure::diagnoseAsError() {
   auto *closure = cast<ClosureExpr>(getAnchor());
   auto params = closure->getParameters();

branches/master-next/lib/Sema/CSDiagnostics.h

@@ -1207,6 +1207,11 @@ class MissingArgumentsFailure final : public FailureDiagnostic {
   /// Diagnose cases when instead of multiple distinct arguments
   /// call got a single tuple argument with expected arity/types.
   bool diagnoseInvalidTupleDestructuring() const;
+
+  /// Determine whether missing arguments are associated with
+  /// an implicit call to a property wrapper initializer e.g.
+  /// `@Foo(answer: 42) var question = "ultimate question"`
+  bool isPropertyWrapperInitialization() const;
 };
 
 class OutOfOrderArgumentFailure final : public FailureDiagnostic {