fix #29936, precompile should not assume UnionAlls have stable addres…

…ses (#31047)

(cherry picked from commit 2dd48b9)

src/dump.c

@@ -255,7 +255,7 @@ static int type_parameter_recursively_external(jl_value_t *p0)
  return 0;
  if (module_in_worklist(p->name->module))
  return 0;
- if (p->name->wrapper != (jl_value_t*)p0) {
+ if (jl_unwrap_unionall(p->name->wrapper) != (jl_value_t*)p) {
  if (!type_recursively_external(p))
  return 0;
  }
@@ -743,7 +743,7 @@ static void jl_serialize_value_(jl_serializer_state *s, jl_value_t *v, int as_li
  else if (jl_is_unionall(v)) {
  write_uint8(s->s, TAG_UNIONALL);
  jl_datatype_t *d = (jl_datatype_t*)jl_unwrap_unionall(v);
- if (jl_is_datatype(d) && d->name->wrapper == v &&
+ if (jl_is_datatype(d) && jl_unwrap_unionall(d->name->wrapper) == (jl_value_t*)d &&
  !module_in_worklist(d->name->module)) {
  write_uint8(s->s, 1);
  jl_serialize_value(s, d->name->module);

test/precompile.jl

@@ -744,5 +744,27 @@ let
  end
 end
 
+# issue #29936
+let
+ load_path = mktempdir()
+ load_cache_path = mktempdir()
+ try
+ write(joinpath(load_path, "Foo29936.jl"),
+ """
+ module Foo29936
+ const global m = Val{nothing}()
+ const global h = Val{:hey}()
+ wab = [("a", m), ("b", h),]
+ end
+ """)
+ pushfirst!(LOAD_PATH, load_path)
+ pushfirst!(DEPOT_PATH, load_cache_path)
+ @eval using Foo29936
+ @test [("Plan", Foo29936.m), ("Plan", Foo29936.h),] isa Vector{Tuple{String,Val}}
+ finally
+ rm(load_path, recursive=true)
+ rm(load_cache_path, recursive=true)
+ end
+end
 
 end # !withenv