[Completion] Complete .isolation for @isolated(any) functions

This was added in SE-0431.

rdar://124615036

Author: hamishknight

include/swift/IDE/CompletionLookup.h

@@ -510,6 +510,9 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
 
   bool tryTupleExprCompletions(Type ExprType);
 
+  /// Try add the completion for '.isolation' for @isolated(any) function types.
+  void tryFunctionIsolationCompletion(Type ExprType);
+
   bool tryFunctionCallCompletions(
       Type ExprType, const ValueDecl *VD,
       std::optional<SemanticContextKind> SemanticContext = std::nullopt);

lib/IDE/CompletionLookup.cpp

@@ -2301,6 +2301,18 @@ bool CompletionLookup::tryTupleExprCompletions(Type ExprType) {
   return true;
 }
 
+void CompletionLookup::tryFunctionIsolationCompletion(Type ExprType) {
+  auto *FT = ExprType->getAs<FunctionType>();
+  if (!FT || !FT->getIsolation().isErased())
+    return;
+
+  // The type of `.isolation` is `(any Actor)?`
+  auto *actorProto = Ctx.getProtocol(KnownProtocolKind::Actor);
+  auto memberTy = OptionalType::get(actorProto->getDeclaredExistentialType());
+
+  addBuiltinMemberRef(Ctx.Id_isolation.str(), memberTy);
+}
+
 bool CompletionLookup::tryFunctionCallCompletions(
     Type ExprType, const ValueDecl *VD,
     std::optional<SemanticContextKind> SemanticContext) {
@@ -2378,6 +2390,9 @@ bool CompletionLookup::tryUnwrappedCompletions(Type ExprType, bool isIUO) {
     }
     if (NumBytesToEraseForOptionalUnwrap <=
         CodeCompletionResult::MaxNumBytesToErase) {
+      // Add '.isolation' to @isolated(any) functions.
+      tryFunctionIsolationCompletion(Unwrapped);
+
       if (!tryTupleExprCompletions(Unwrapped)) {
         lookupVisibleMemberDecls(*this, Unwrapped, DotLoc,
                                  CurrDeclContext,
@@ -2453,6 +2468,10 @@ void CompletionLookup::getValueExprCompletions(Type ExprType, ValueDecl *VD,
     ExprType = OptionalType::get(ExprType);
 
   // Handle special cases
+
+  // Add '.isolation' to @isolated(any) functions.
+  tryFunctionIsolationCompletion(ExprType);
+
   bool isIUO = VD && VD->isImplicitlyUnwrappedOptional();
   if (tryFunctionCallCompletions(ExprType, IsDeclUnapplied ? VD : nullptr))
     return;

test/IDE/complete_function_isolation.swift

@@ -0,0 +1,24 @@
+// RUN: %batch-code-completion
+
+// REQUIRES: concurrency
+
+func test1(_ x: () -> Void) {
+  x.#^NORMAL_FN^#
+  // NORMAL_FN:     Begin completions, 2 items
+  // NORMAL_FN-DAG: Keyword[self]/CurrNominal: self[#() -> Void#]; name=self
+  // NORMAL_FN-DAG: Pattern/CurrModule/Flair[ArgLabels]/Erase[1]: ()[#Void#]; name=()
+}
+
+func test2(_ x: @isolated(any) () -> Void) {
+  x.#^ISOLATED_ANY_FN^#
+  // ISOLATED_ANY_FN:     Begin completions, 3 items
+  // ISOLATED_ANY_FN-DAG: Pattern/CurrNominal: isolation[#(any Actor)?#]; name=isolation
+  // ISOLATED_ANY_FN-DAG: Keyword[self]/CurrNominal: self[#@isolated(any) () -> Void#]; name=self
+  // ISOLATED_ANY_FN-DAG: Pattern/CurrModule/Flair[ArgLabels]/Erase[1]: ()[#Void#]; name=()
+}
+
+func test3(_ x: (@isolated(any) () -> Void)?) {
+  x.#^ISOLATED_ANY_OPTIONAL_FN^#
+  // ISOLATED_ANY_OPTIONAL_FN-DAG: Pattern/CurrNominal/Erase[1]: ?.isolation[#(any Actor)?#]; name=isolation
+  // ISOLATED_ANY_OPTIONAL_FN-DAG: Keyword[self]/CurrNominal: self[#(@isolated(any) () -> Void)?#]; name=self
+}