[CodeCompletion] Look through optional when determining the function type of a called overload

rdar://97339983

Author: ahoppen

include/swift/IDE/ArgumentCompletion.h

@@ -30,7 +30,7 @@ class ArgumentTypeCheckCompletionCallback : public TypeCheckCompletionCallback {
     /// The FuncDecl or SubscriptDecl associated with the call.
     ValueDecl *FuncD;
     /// The type of the function being called.
-    Type FuncTy;
+    AnyFunctionType *FuncTy;
     /// The index of the argument containing the completion location
     unsigned ArgIdx;
     /// The index of the parameter corresponding to the completion argument.

lib/IDE/ArgumentCompletion.cpp

@@ -36,8 +36,7 @@ bool ArgumentTypeCheckCompletionCallback::addPossibleParams(
     return true;
   }
 
-  ArrayRef<AnyFunctionType::Param> ParamsToPass =
-      Res.FuncTy->getAs<AnyFunctionType>()->getParams();
+  ArrayRef<AnyFunctionType::Param> ParamsToPass = Res.FuncTy->getParams();
 
   ParameterList *PL = nullptr;
   if (Res.FuncD) {
@@ -167,8 +166,12 @@ void ArgumentTypeCheckCompletionCallback::sawSolutionImpl(const Solution &S) {
   llvm::SmallDenseMap<const VarDecl *, Type> SolutionSpecificVarTypes;
   getSolutionSpecificVarTypes(S, SolutionSpecificVarTypes);
 
+  AnyFunctionType *FuncTy = nullptr;
+  if (Info.ValueTy) {
+    FuncTy = Info.ValueTy->lookThroughAllOptionalTypes()->getAs<AnyFunctionType>();
+  }
   Results.push_back({ExpectedTy, isa<SubscriptExpr>(ParentCall), Info.Value,
-                     Info.ValueTy, ArgIdx, ParamIdx, std::move(ClaimedParams),
+                     FuncTy, ArgIdx, ParamIdx, std::move(ClaimedParams),
                      IsNoninitialVariadic, Info.BaseTy, HasLabel, IsAsync,
                      SolutionSpecificVarTypes});
 }
@@ -216,8 +219,7 @@ void ArgumentTypeCheckCompletionCallback::deliverResults(
         }
       }
       if (Result.FuncTy) {
-        if (auto FuncTy = Result.FuncTy->lookThroughAllOptionalTypes()
-                              ->getAs<AnyFunctionType>()) {
+        if (auto FuncTy = Result.FuncTy) {
           if (Result.IsSubscript) {
             assert(SemanticContext != SemanticContextKind::None);
             auto *SD = dyn_cast_or_null<SubscriptDecl>(Result.FuncD);

test/IDE/complete_optional_function.swift

@@ -0,0 +1,9 @@
+// RUN: %empty-directory(%t) 
+// RUN: %target-swift-ide-test -batch-code-completion -source-filename %s -filecheck %raw-FileCheck -completion-output-dir %t
+
+func foo(_ x: ((_ x: Int, _ y: Int) -> Void)?) {
+  x?(1, #^OPTIONAL_PARAMETER^#)
+  // OPTIONAL_PARAMETER: Begin completions
+  // OPTIONAL_PARAMETER-DAG: Literal[Integer]/None/TypeRelation[Convertible]: 0[#Int#]; name=0
+  // OPTIONAL_PARAMETER: End completions
+}