asn1: Fix IMPLICIT tagging (codegen)

lib/asn1/gen.c

@@ -551,6 +551,41 @@ generate_constant (const Symbol *s)
     }
 }
 
+int
+is_tagged_type(const Type *t)
+{
+    /*
+     * Start by chasing aliasings like this:
+     *
+     * Type0 ::= ...
+     * Type1 ::= Type0
+     * ..
+     * TypeN ::= TypeN-1
+     *
+     * to <Type0>, then check if <Type0> is tagged.
+     */
+    while (t->type == TType) {
+        if (t->subtype)
+            t = t->subtype;
+        else if (t->symbol && t->symbol->type)
+            t = t->symbol->type;
+        else
+            abort();
+
+    }
+    if (t->type == TTag && t->tag.tagenv == TE_EXPLICIT)
+        return 1;
+    if (t->type == TTag) {
+        if (t->subtype)
+            return is_tagged_type(t->subtype);
+        if (t->symbol && t->symbol->type)
+            return is_tagged_type(t->symbol->type);
+        /* This is the tag */
+        return 1;
+    }
+    return 0;
+}
+
 int
 is_primitive_type(const Type *t)
 {

lib/asn1/gen_decode.c

@@ -533,7 +533,7 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
             else if (t->subtype->symbol && strcmp(t->subtype->symbol->name, "HEIM_ANY"))
                 replace_tag = 1;
         } else if (t->tag.tagenv == TE_IMPLICIT && prim && t->subtype->symbol)
-            replace_tag = 1;
+            replace_tag = is_tagged_type(t->subtype->symbol->type);
 
 	if (asprintf(&typestring, "%s_type", tmpstr) < 0 || typestring == NULL)
 	    errx(1, "malloc");

lib/asn1/gen_encode.c

@@ -457,7 +457,7 @@ encode_type (const char *name, const Type *t, const char *tmpstr)
              * functions, and those will be adding their UNIVERSAL or whatever
              * tags unlike our raw primtive codec library.
              */
-            replace_tag = 1;
+            replace_tag = is_tagged_type(t->subtype->symbol->type);
 
         if (replace_tag)
             fprintf(codefile,

lib/asn1/gen_length.c

@@ -266,7 +266,7 @@ length_type (const char *name, const Type *t,
             else if (t->subtype->symbol && strcmp(t->subtype->symbol->name, "heim_any"))
                 replace_tag = 1;
         } else if (t->tag.tagenv == TE_IMPLICIT && prim && t->subtype->symbol)
-            replace_tag = 1;
+            replace_tag = is_tagged_type(t->subtype->symbol->type);
         if (replace_tag)
             /*
              * We're replacing the tag of the underlying type.  If that type is

lib/asn1/gen_locl.h

@@ -138,6 +138,7 @@ void add_export(const char *);
 int is_export(const char *);
 int yyparse(void);
 int is_primitive_type(const Type *);
+int is_tagged_type(const Type *);
 
 int preserve_type(const char *);
 int seq_type(const char *);