ww package: reject non-function main declarations

cmd/wcc/check.c

@@ -3885,6 +3885,35 @@ classify_init_decls(Checker *c, Node *file)
 	}
 }
 
+/* Pinned Go 1.26.5 types2 rejects a non-function package-scope `main`
+ * before declaring it, but only when the declared package name is `main`
+ * (resolver.go:90-110 declarePkgObj). WW's function entry ABI deliberately
+ * permits argument/result-bearing functions, so this is the independent
+ * declaration-kind rule: canonical identity, physical directory, path leaf,
+ * and root/action status are not inputs. Remove rejected declarations from
+ * later name installation just as the pinned resolver returns without
+ * declaring its object. */
+static void
+reject_nonfunction_main_decls(Checker *c, Node *file)
+{
+	Node *prev = NULL;
+	for (Node *d = file->list; d; ) {
+		Node *next = d->next;
+		int invalid = top_decl_kind(d) && d->kind != N_FNDECL
+		    && d->str != NULL && strcmp(d->str, "main") == 0
+		    && d->pkgname != NULL && strcmp(d->pkgname, "main") == 0;
+		if (invalid) {
+			err(c, d->pos, "cannot declare main - must be func");
+			if (prev == NULL)
+				file->list = next;
+			else
+				prev->next = next;
+		} else
+			prev = d;
+		d = next;
+	}
+}
+
 /* Import usage is a property of the file-local qualifier occurrence. Record
  * qualified syntax before resolving declaration bodies so import diagnostics
  * retain production Go's source order without making a failed bare lookup a
@@ -4049,6 +4078,7 @@ check_file(Checker *c, Node *file)
 			file->list = usenode;
 		}
 	}
+	reject_nonfunction_main_decls(c, file);
 	mark_import_uses(c, file);
 	check_import_redeclarations(c, file);
 	check_import_usage_and_collisions(c, file);