Clean up tydesc declaration to make it clear what is unused.

src/rt/rust_type.h

@@ -42,29 +42,24 @@ static inline void *box_body(rust_opaque_box *box) {
     return (void*)(box + 1);
 }
 
+// N.B. If you want to add a field to tydesc, please use one of the
+// unused fields!
 struct type_desc {
-    // First part of type_desc is known to compiler.
-    // first_param = &descs[1] if dynamic, null if static.
     const type_desc **first_param;
     size_t size;
     size_t align;
     glue_fn *take_glue;
     glue_fn *drop_glue;
     glue_fn *free_glue;
-    void *UNUSED;
-    glue_fn *sever_glue;    // For GC.
-    glue_fn *mark_glue;     // For GC.
-    uintptr_t unused2;
-    void *UNUSED_2;
+    glue_fn *visit_glue;
+    uintptr_t UNUSED_1;
+    uintptr_t UNUSED_2;
+    uintptr_t UNUSED_3;
+    uintptr_t UNUSED_4;
     const uint8_t *shape;
     const rust_shape_tables *shape_tables;
-    uintptr_t n_params;
-    uintptr_t n_obj_params;
-
-    // Residual fields past here are known only to runtime.
-    UT_hash_handle hh;
-    size_t n_descs;
-    const type_desc *descs[];
+    uintptr_t UNUSED_5;
+    uintptr_t UNUSED_6;
 };
 
 extern "C" type_desc *rust_clone_type_desc(type_desc*);

src/rustc/middle/trans/base.rs

@@ -630,14 +630,14 @@ fn emit_tydescs(ccx: @crate_ctxt) {
                             drop_glue, // drop_glue
                             free_glue, // free_glue
                             visit_glue, // visit_glue
-                            C_null(glue_fn_ty), // sever_glue
-                            C_null(glue_fn_ty), // mark_glue
-                            C_null(glue_fn_ty), // unused
-                            C_null(T_ptr(T_i8())), // cmp_glue
+                            C_int(ccx, 0), // ununsed
+                            C_int(ccx, 0), // ununsed
+                            C_int(ccx, 0), // ununsed
+                            C_int(ccx, 0), // ununsed
                             C_shape(ccx, shape), // shape
                             shape_tables, // shape_tables
-                            C_int(ccx, 0), // n_params
-                            C_int(ccx, 0)]); // n_obj_params
+                            C_int(ccx, 0), // ununsed
+                            C_int(ccx, 0)]); // unused
 
         let gvar = ti.tydesc;
         llvm::LLVMSetInitializer(gvar, tydesc);

src/rustc/middle/trans/common.rs

@@ -621,7 +621,7 @@ fn T_tydesc(targ_cfg: @session::config) -> TypeRef {
     let elems =
         [tydescpp, int_type, int_type,
          glue_fn_ty, glue_fn_ty, glue_fn_ty, glue_fn_ty,
-         glue_fn_ty, glue_fn_ty, glue_fn_ty, T_ptr(T_i8()),
+         int_type, int_type, int_type, int_type,
          T_ptr(T_i8()), T_ptr(T_i8()), int_type, int_type];
     set_struct_body(tydesc, elems);
     ret tydesc;