Add Dump methods to printable types. (#681)

executable_semantics/ast/expression.h

@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "common/ostream.h"
+#include "llvm/Support/Compiler.h"
 
 namespace Carbon {
 
@@ -179,6 +180,7 @@ struct Expression {
   auto GetFunctionTypeLiteral() const -> const FunctionTypeLiteral&;
 
   void Print(llvm::raw_ostream& out) const;
+  LLVM_DUMP_METHOD void Dump() const { Print(llvm::errs()); }
 
   inline auto tag() const -> ExpressionKind {
     return std::visit([](const auto& t) { return t.Kind; }, value);