Using structs with unary operators

Per section 5.7 of the WebGL spec, the only operators allowed on structs are field selector, equality and assignment. No unary operators are allowed.
This test verifies unary operators used on structures are disallowed.

Shader is of the form:
precision mediump float;
struct S { $(type) t; };
void main() {
    S a;
    a.t = $(initializer);
    S b = $(operator)a;   // Unary operators not allowed
    gl_FragColor = $(fragColor);
}