Example:

struct S { i : i32 };
fn f() {
   S();  // @ben-clayton asked: is this valid, by spec?
}

That would match func_call_statement which breaks down to a callable followed by an argument list. And a callable is an ident or a type-specifier-without-ident.
So syntactically it parses.

We use type checking to match to the type-constructor expression, which then gives the semantics.

However, the spec needs to make clear that type constructor expressions execute as if they are function calls. This is how we fit it into behaviour analysis and uniformity analysis. Behaviour analysis tables are given as pattern matches, so that probably already is covered. But we'd need the clarification to ensure type constructors are covered by the uniformity analysis for function calls.
https://gpuweb.github.io/gpuweb/wgsl/#uniformity-function-calls