1 files changed, 52 insertions, 3 deletions

diff --git a/src/wasm-type.h b/src/wasm-type.h
index 8c8d85ebf..29e5114b7 100644
--- a/src/wasm-type.h
+++ b/src/wasm-type.h
@@ -17,14 +17,18 @@
 #ifndef wasm_wasm_type_h
 #define wasm_wasm_type_h
 
-#include "support/name.h"
-#include "support/parent_index_iterator.h"
-#include "wasm-features.h"
+#include <functional>
 #include <optional>
 #include <ostream>
+#include <string>
 #include <variant>
 #include <vector>
 
+#include "support/index.h"
+#include "support/name.h"
+#include "support/parent_index_iterator.h"
+#include "wasm-features.h"
+
 // TODO: At various code locations we were assuming that single types are basic
 // types, but this is going to change with the introduction of the compound
 // Signature, Struct and Array types that will be single but not basic. To
@@ -68,6 +72,17 @@ struct Rtt;
 enum Nullability { NonNullable, Nullable };
 enum Mutability { Immutable, Mutable };
 
+// HeapType name information used for printing.
+struct TypeNames {
+  // The name of the type.
+  Name name;
+  // For a Struct, names of fields.
+  std::unordered_map<Index, Name> fieldNames;
+};
+
+// Used to generate HeapType names.
+using HeapTypeNameGenerator = std::function<TypeNames(HeapType)>;
+
 // The type used for interning IDs in the public interfaces of Type and
 // HeapType.
 using TypeID = uint64_t;
@@ -271,6 +286,22 @@ public:
     return lub;
   }
 
+  // Helper allowing the value of `print(...)` to be sent to an ostream. Stores
+  // a `TypeID` because `Type` is incomplete at this point and using a reference
+  // makes it less convenient to use.
+  struct Printed {
+    TypeID typeID;
+    HeapTypeNameGenerator generateName;
+  };
+
+  // Given a function for generating non-basic HeapType names, print this Type
+  // to `os`.`generateName` should return the same name each time it is called
+  // with the same HeapType and it should return different names for different
+  // types.
+  Printed print(HeapTypeNameGenerator generateName) {
+    return Printed{getID(), generateName};
+  }
+
   std::string toString() const;
 
   size_t size() const;
@@ -385,6 +416,22 @@ public:
   // Return the LUB of two HeapTypes. The LUB always exists.
   static HeapType getLeastUpperBound(HeapType a, HeapType b);
 
+  // Helper allowing the value of `print(...)` to be sent to an ostream. Stores
+  // a `TypeID` because `Type` is incomplete at this point and using a reference
+  // makes it less convenient to use.
+  struct Printed {
+    TypeID typeID;
+    HeapTypeNameGenerator generateName;
+  };
+
+  // Given a function for generating HeapType names, print the definition of
+  // this HeapType to `os`. `generateName` should return the same
+  // name each time it is called with the same HeapType and it should return
+  // different names for different types.
+  Printed print(HeapTypeNameGenerator generateName) {
+    return Printed{getID(), generateName};
+  }
+
   std::string toString() const;
 };
 
@@ -667,7 +714,9 @@ struct TypeBuilder {
 };
 
 std::ostream& operator<<(std::ostream&, Type);
+std::ostream& operator<<(std::ostream&, Type::Printed);
 std::ostream& operator<<(std::ostream&, HeapType);
+std::ostream& operator<<(std::ostream&, HeapType::Printed);
 std::ostream& operator<<(std::ostream&, Tuple);
 std::ostream& operator<<(std::ostream&, Signature);
 std::ostream& operator<<(std::ostream&, Field);