[BuilderTransform] Add contextual type to transformation information

This information would be used to decide whether conjunction that
represents transformed closure should be delayed or not.

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -985,6 +985,11 @@ struct AppliedBuilderTransform {
   /// converted. Opaque types should be unopened.
   Type bodyResultType;
 
+  /// If transform is applied to a closure, this type represents
+  /// contextual type the closure is converted type (e.g. a parameter
+  /// type or or pattern type).
+  Type contextualType;
+
   /// The version of the original body with result builder applied
   /// as AST transformation.
   NullablePtr<BraceStmt> transformedBody;
@@ -5727,7 +5732,7 @@ class ConstraintSystem {
   Optional<TypeMatchResult>
   matchResultBuilder(AnyFunctionRef fn, Type builderType, Type bodyResultType,
                      ConstraintKind bodyResultConstraintKind,
-                     ConstraintLocatorBuilder locator);
+                     Type contextualType, ConstraintLocatorBuilder locator);
 
   /// Matches a wrapped or projected value parameter type to its backing
   /// property wrapper type by applying the property wrapper.

lib/Sema/BuilderTransform.cpp

@@ -2341,6 +2341,7 @@ Optional<BraceStmt *> TypeChecker::applyResultBuilderBodyTransform(
 
   if (auto result = cs.matchResultBuilder(
           func, builderType, resultContextType, resultConstraintKind,
+          /*contextualType=*/Type(),
           cs.getConstraintLocator(func->getBody()))) {
     if (result->isFailure())
       return nullptr;
@@ -2428,6 +2429,7 @@ Optional<ConstraintSystem::TypeMatchResult>
 ConstraintSystem::matchResultBuilder(AnyFunctionRef fn, Type builderType,
                                      Type bodyResultType,
                                      ConstraintKind bodyResultConstraintKind,
+                                     Type contextualType,
                                      ConstraintLocatorBuilder locator) {
   builderType = simplifyType(builderType);
   auto builder = builderType->getAnyNominal();
@@ -2552,6 +2554,7 @@ ConstraintSystem::matchResultBuilder(AnyFunctionRef fn, Type builderType,
 
     transformInfo.builderType = builderType;
     transformInfo.bodyResultType = bodyResultType;
+    transformInfo.contextualType = contextualType;
     transformInfo.transformedBody = transformedBody->second;
 
     // Record the transformation.

lib/Sema/CSSimplify.cpp

@@ -11037,7 +11037,7 @@ bool ConstraintSystem::resolveClosure(TypeVariableType *typeVar,
   if (resultBuilderType) {
     if (auto result = matchResultBuilder(
             closure, resultBuilderType, closureType->getResult(),
-            ConstraintKind::Conversion, locator)) {
+            ConstraintKind::Conversion, contextualType, locator)) {
       return result->isSuccess();
     }
   }