184 reject omitted required expression param

// PIN — an `Expression` input is a parameter like any other: omit a required
// one and the call is refused.
//
// The twin of 400_183 for the comptime side, and it was MORE silent: an omitted
// required `Expression` param built clean with no Zig error at all, because an
// Expression's value is captured source text rather than a struct field, so
// there is nothing for the host compiler to miss.
//
// `expr` is exempt from nothing here — it is required (400_187 pins that it
// cannot be optional) and it is filled by the first positional. `suffix` is an
// ordinary named parameter that happens to carry an expression, and must be
// labelled.
~import std/io

~[expand]pub tor shout { expr: Expression, suffix: Expression }

~[template]proc shout|zig {
{{ expr }}
}

~shout("hi")