compilation test for conditional threadlocal storage

lib/std/testing.zig

@@ -916,6 +916,26 @@ test "expectEqualDeep composite type" {
     }
 }
 
+// TODO: test blocks can observe their own index fn argument.
+// Do not leaks implementation details from the test runner into libstd.
+// `test_fns_i` is index into builtin.test_functions set by test runner.
+const TestFn_iT = if (!builtin.is_test) u32 else void;
+threadlocal var test_fns_i: TestFn_iT = if (!builtin.is_test) 0 else void;
+
+/// Send expected panic message to server from test runner, spawns itself as a
+/// child process with the test number, tells the server pid and process group
+/// of child and waits for the child process. The child process executes exactly
+/// one test block up to panic or returns with error code 1.
+/// If another expected panic message has been received by the server for the
+/// same test block, then the test is marked as error.InvalidPanicMsg and the
+/// child of the test runner thread is terminated via pid and process group,
+///
+/// In case no server is desired, the to be run test block is provided as cli
+/// argument.
+pub fn expectPanic(msg: []const u8) !void {
+    _ = msg;
+}
+
 fn printIndicatorLine(source: []const u8, indicator_index: usize) void {
     const line_begin_index = if (std.mem.lastIndexOfScalar(u8, source[0..indicator_index], '\n')) |line_begin|
         line_begin + 1

lib/std/zig/Server.zig

@@ -42,7 +42,7 @@ pub const Message = struct {
     ///   - 0 means not async
     /// * expected_panic_msg: [tests_len]u32,
     ///   - null-terminated string_bytes index
-    ///   - 0 means does not expect pani
+    ///   - 0 means does not expect panic
     /// * string_bytes: [string_bytes_len]u8,
     pub const TestMetadata = extern struct {
         string_bytes_len: u32,

lib/test_runner.zig

@@ -146,6 +146,7 @@ fn mainTerminal() void {
 
     var leaks: usize = 0;
     for (test_fn_list, 0..) |test_fn, i| {
+        std.testing.test_fns_i = i;
         std.testing.allocator_instance = .{};
         defer {
             if (std.testing.allocator_instance.deinit() == .leak) {