Update Types.h

Fix a type collision that exists with delayed template instantiation. This header is used in LLDB and in Swift and the type is ambiguous when not forward declared.

Author: compnerd

include/swift/AST/Types.h

@@ -352,6 +352,9 @@ enum class TypeMatchFlags {
 };
 using TypeMatchOptions = OptionSet<TypeMatchFlags>;
 
+// Forward declare the ErrorType as otherwise we will match `lldb::ErrorType`.
+class ErrorType;
+
 /// Base class for all types which describe the Swift and SIL ASTs.
 ///
 /// See TypeNodes.def for a succinct description of the full class hierarchy.