From efd2069f0c43fed7cde40478f5ef2de266f0de5e Mon Sep 17 00:00:00 2001
From: Pavel Yaskevich <pyaskevich@apple.com>
Date: Wed, 17 Oct 2018 17:35:22 -0700
Subject: [PATCH] [CSDiag] Don't increase candidate curry level if base is
 ignored

When `CandidateCalleeInfo` tries to create a candidate for expression
in form of `<base>.<func>` it shouldn't assume that function type of
'<func>' would always be at curry level 1, because base could be ignored
when it is a module or 'b' refers to a static function.

Resolves: rdar://problem/45242032
---
 lib/Sema/CalleeCandidateInfo.cpp    | 11 ++++++++++-
 test/Constraints/rdar45242032.swift | 22 ++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 test/Constraints/rdar45242032.swift

diff --git a/lib/Sema/CalleeCandidateInfo.cpp b/lib/Sema/CalleeCandidateInfo.cpp
index 16dee0066d1df..26f9ed88e5794 100644
--- a/lib/Sema/CalleeCandidateInfo.cpp
+++ b/lib/Sema/CalleeCandidateInfo.cpp
@@ -717,7 +717,16 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
   if (auto UDE = dyn_cast<UnresolvedDotExpr>(fn)) {
     declName = UDE->getName().getBaseName().userFacingName();
     uncurryLevel = 1;
-    
+
+    // If base is a module or metatype, this is just a simple
+    // reference so its curry level should be 0.
+    if (auto *DRE = dyn_cast<DeclRefExpr>(UDE->getBase())) {
+      if (auto baseType = DRE->getType())
+        uncurryLevel =
+            (baseType->is<ModuleType>() || baseType->is<AnyMetatypeType>()) ? 0
+                                                                            : 1;
+    }
+
     // If we actually resolved the member to use, return it.
     auto loc = CS.getConstraintLocator(UDE, ConstraintLocator::Member);
     if (auto *member = CS.findResolvedMemberRef(loc)) {
diff --git a/test/Constraints/rdar45242032.swift b/test/Constraints/rdar45242032.swift
new file mode 100644
index 0000000000000..3e24e88c96dea
--- /dev/null
+++ b/test/Constraints/rdar45242032.swift
@@ -0,0 +1,22 @@
+// RUN: %target-typecheck-verify-swift -module-name M
+
+protocol P {
+  var v: String { get }
+}
+
+func foo(bar: [P], baz: [P]) {
+// expected-note@-1 {{'foo(bar:baz:)' declared here}}
+}
+
+struct S {
+  static func bar(fiz: [P], baz: [P]) {}
+// expected-note@-1 {{'bar(fiz:baz:)' declared here}}
+}
+
+do {
+  let _ = M.foo(bar & // expected-error {{missing argument for parameter 'bar' in call}}
+} // expected-error {{expected expression after operator}}
+
+do {
+  let _ = S.bar(fiz & // expected-error {{missing argument for parameter 'fiz' in call}}
+} // expected-error {{expected expression after operator}}