[sending] Fix type inference for sending results of closures.

The previous commit fixed things like:

```swift
let x: () -> sending String = { "" }
```

This commit fixes this test case:

```swift
let x = { () -> sending String in "" }
```

Author: gottesmm

lib/Sema/CSGen.cpp

@@ -1649,10 +1649,9 @@ namespace {
     }
 
     Type
-    resolveTypeReferenceInExpression(TypeRepr *repr, TypeResolverContext resCtx,
+    resolveTypeReferenceInExpression(TypeRepr *repr,
+                                     TypeResolutionOptions options,
                                      const ConstraintLocatorBuilder &locator) {
-      TypeResolutionOptions options(resCtx);
-
       // Introduce type variables for unbound generics.
       const auto genericOpener = OpenUnboundGenericType(CS, locator);
       const auto placeholderHandler = HandlePlaceholderType(CS, locator);
@@ -2541,9 +2540,11 @@ namespace {
             return declaredTy;
           }
 
+          auto options =
+              TypeResolutionOptions(TypeResolverContext::InExpression);
+          options.setContext(TypeResolverContext::ClosureExpr);
           const auto resolvedTy = resolveTypeReferenceInExpression(
-              closure->getExplicitResultTypeRepr(),
-              TypeResolverContext::InExpression, resultLocator);
+              closure->getExplicitResultTypeRepr(), options, resultLocator);
           if (resolvedTy)
             return resolvedTy;
         }

lib/Sema/TypeCheckType.cpp

@@ -4971,7 +4971,8 @@ TypeResolver::resolveSendingTypeRepr(SendingTypeRepr *repr,
     return ErrorType::get(getASTContext());
   }
 
-  if (!options.is(TypeResolverContext::FunctionResult) &&
+  if (!options.is(TypeResolverContext::ClosureExpr) &&
+      !options.is(TypeResolverContext::FunctionResult) &&
       (!options.is(TypeResolverContext::FunctionInput) ||
        options.hasBase(TypeResolverContext::EnumElementDecl))) {
     diagnoseInvalid(repr, repr->getSpecifierLoc(),

lib/Sema/TypeCheckType.h

@@ -118,7 +118,7 @@ enum class TypeResolverContext : uint8_t {
   /// Whether we are checking the parameter list of a subscript.
   SubscriptDecl,
 
-  /// Whether we are checking the parameter list of a closure.
+  /// Whether we are checking the parameter list or result of a closure.
   ClosureExpr,
 
   /// Whether we are in the input type of a function, or under one level of

test/Concurrency/sending_closure_inference.swift

@@ -42,3 +42,7 @@ func testNamedTypeParameterSendingInference() {
 func testSendingResultInference() {
   let _: () -> sending String = { "" }
 }
+
+func testSendingResultOnClosure() {
+  let _ = { (x: String) -> sending String in x }
+}