parser: port test "top-level bare asterisk+asterisk+identifier"

Implement ** (double pointer) type parsing in parseTypeExpr.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

parser.c

@@ -839,10 +839,25 @@ static AstNodeIndex parseTypeExpr(Parser* p) {
                 .data = { .lhs = 0, .rhs = child_type },
             });
     }
-    case TOKEN_ASTERISK_ASTERISK:
-        fprintf(stderr, "parseTypeExpr not supported for %s\n",
-            tokenizerGetTagString(tok));
-        exit(1);
+    case TOKEN_ASTERISK_ASTERISK: {
+        // ** is two nested pointer types sharing the same token
+        const AstTokenIndex asterisk = nextToken(p);
+        // Inner pointer: parse modifiers and child type
+        const AstNodeIndex inner_child = parseTypeExpr(p);
+        const AstNodeIndex inner = addNode(&p->nodes,
+            (AstNodeItem) {
+                .tag = AST_NODE_PTR_TYPE_ALIGNED,
+                .main_token = asterisk,
+                .data = { .lhs = 0, .rhs = inner_child },
+            });
+        // Outer pointer wraps the inner
+        return addNode(&p->nodes,
+            (AstNodeItem) {
+                .tag = AST_NODE_PTR_TYPE_ALIGNED,
+                .main_token = asterisk,
+                .data = { .lhs = 0, .rhs = inner },
+            });
+    }
     case TOKEN_L_BRACKET: {
         const AstTokenIndex lbracket = nextToken(p);
         if (p->token_tags[p->tok_i] == TOKEN_ASTERISK) {

parser_test.zig

@@ -1812,3 +1812,10 @@ test "zig fmt: top-level bare asterisk+identifier" {
         \\
     );
 }
+
+test "zig fmt: top-level bare asterisk+asterisk+identifier" {
+    try testCanonical(
+        \\**x
+        \\
+    );
+}