[AssociatedTypeInference] Strip 'self' parameter from function type of an enum case witness (swiftlang#32768)

Author: theblixguy

lib/Sema/TypeCheckProtocolInference.cpp

@@ -549,9 +549,8 @@ static Type getWitnessTypeForMatching(NormalProtocolConformance *conformance,
 
 /// Remove the 'self' type from the given type, if it's a method type.
 static Type removeSelfParam(ValueDecl *value, Type type) {
-  if (auto func = dyn_cast<AbstractFunctionDecl>(value)) {
-    if (func->getDeclContext()->isTypeContext())
-      return type->castTo<AnyFunctionType>()->getResult();
+  if (value->hasCurriedSelf()) {
+    return type->castTo<AnyFunctionType>()->getResult();
   }
 
   return type;

test/decl/protocol/req/associated_type_inference.swift

@@ -527,3 +527,22 @@ extension S30 {
     T.bar()
   }
 }
+
+// SR-13172: Inference when witness is an enum case
+protocol SR_13172_P1 {
+  associatedtype Bar
+  static func bar(_ value: Bar) -> Self
+}
+
+enum SR_13172_E1: SR_13172_P1 {
+  case bar(String) // Okay
+}
+
+protocol SR_13172_P2 {
+  associatedtype Bar
+  static var bar: Bar { get }
+}
+
+enum SR_13172_E2: SR_13172_P2 {
+  case bar // Okay
+}