Merge pull request swiftlang#21931 from xedin/rdar-47324309

[ConstraintSystem] Mark generic parameter bindings as potentially inc…

Author: xedin

lib/Sema/ConstraintSystem.h

@@ -2871,7 +2871,8 @@ class ConstraintSystem {
     /// A set of all constraints which contribute to pontential bindings.
     llvm::SmallPtrSet<Constraint *, 8> Sources;
 
-    PotentialBindings(TypeVariableType *typeVar) : TypeVar(typeVar) {}
+    PotentialBindings(TypeVariableType *typeVar)
+        : TypeVar(typeVar), PotentiallyIncomplete(isGenericParameter()) {}
 
     /// Determine whether the set of bindings is non-empty.
     explicit operator bool() const { return !Bindings.empty(); }
@@ -2937,6 +2938,16 @@ class ConstraintSystem {
     /// Check if this binding is viable for inclusion in the set.
     bool isViable(PotentialBinding &binding) const;
 
+    bool isGenericParameter() const {
+      if (auto *locator = TypeVar->getImpl().getLocator()) {
+        auto path = locator->getPath();
+        return path.empty() ? false
+                            : path.back().getKind() ==
+                                  ConstraintLocator::GenericParameter;
+      }
+      return false;
+    }
+
     void dump(llvm::raw_ostream &out,
               unsigned indent = 0) const LLVM_ATTRIBUTE_USED {
       out.indent(indent);

test/Constraints/sr9626.swift

@@ -0,0 +1,22 @@
+// RUN: %target-swift-frontend -emit-sil -verify %s | %FileCheck %s
+
+class BaseClass {}
+class SubClass: BaseClass {}
+struct Box<T> { init(_: T.Type) {} }
+
+
+func test1<T>(box: Box<T>) -> T.Type {
+  return T.self
+}
+
+func test2<T: BaseClass>(box: Box<T>) -> T.Type {
+  return T.self
+}
+
+// CHECK: [[F1:%.*]] = function_ref @$s6sr96263BoxVyACyxGxmcfC
+// CHECK-NEXT: apply [[F1]]<SubClass>({{.*}}, {{.*}})
+_ = test1(box: .init(SubClass.self))
+
+// CHECK: [[F2:%.*]] = function_ref @$s6sr96265test23boxxmAA3BoxVyxG_tAA9BaseClassCRbzlF
+// CHECK-NEXT: apply [[F2]]<SubClass>({{.*}})
+_ = test2(box: .init(SubClass.self))