[ConstraintSystem] Add a way to check whether a given type variable represents a closure parameter type

Author: xedin

lib/Sema/ConstraintSystem.h

@@ -301,6 +301,10 @@ class TypeVariableType::Implementation {
   /// Determine whether this type variable represents a closure type.
   bool isClosureType() const;
 
+  /// Determine whether this type variable represents one of the
+  /// parameter types associated with a closure.
+  bool isClosureParameterType() const;
+
   /// Determine whether this type variable represents a closure result type.
   bool isClosureResultType() const;
 

lib/Sema/TypeCheckConstraints.cpp

@@ -90,6 +90,14 @@ bool TypeVariableType::Implementation::isClosureType() const {
   return isExpr<ClosureExpr>(locator->getAnchor()) && locator->getPath().empty();
 }
 
+bool TypeVariableType::Implementation::isClosureParameterType() const {
+  if (!(locator && locator->getAnchor()))
+    return false;
+
+  return isExpr<ClosureExpr>(locator->getAnchor()) &&
+         locator->isLastElement<LocatorPathElt::TupleElement>();
+}
+
 bool TypeVariableType::Implementation::isClosureResultType() const {
   if (!(locator && locator->getAnchor()))
     return false;