Improve error message when encountering a trailing character in source code

[zxubian]

Zig Version

0.11.0-dev.945+0c30e006c

Steps to Reproduce and Observed Output

Both of the following examples produce an unhelpful error message:

const std = @import("std");
pub fn main() !void {
    std.log.info("Hello, World!", .{});
} w

repro.zig:1:1: error: tuple declarations cannot contain declarations
const std = @import("std");
^~~~~~~~~~~~~~~~~~~~~~~~~~

test "Empty"{

} w

repro.zig:1:1: error: tuple declarations cannot contain declarations
test "Empty" {
^~~~

Expected Output

Expected a more helpful error message, e.g.:

error: unexpected character 'w'
} w
~~^~~~~~~~~~~~~~~~~~~~~~~~~~

Error message should correctly point to the incorrect character/symbol/token.