Merge pull request #16918 from gottesmm/swift-4.2-branch-get-ast-type

[4.2] Ease cherry-picking by providing an impl of SILType::getASTType().

Author: gottesmm

include/swift/SIL/SILType.h

@@ -158,6 +158,11 @@ class SILType {
     return SILType(getSwiftRValueType(), SILValueCategory::Object);
   }
 
+  /// Returns the canonical AST type referenced by this SIL type.
+  CanType getASTType() const {
+    return getSwiftRValueType();
+  }
+
   /// Returns the Swift type referenced by this SIL type.
   CanType getSwiftRValueType() const {
     return CanType(value.getPointer());