Hwaro::Assets::Sass::ShapeMismatch
Inherits Exception / Reference / Object
"This call isn't mine" — raised by a built-in whose name shadows a
real CSS function (rgba(), grayscale(), saturate(), …) when
the arguments are the CSS shape rather than the Sass one.
Deliberately NOT a SoftEvalError. A SoftEvalError unwinds the whole
declaration to verbatim text, which drags every other expression in
it down too — filter: grayscale(50%) blur($r * 1px) would ship
blur(2 * 1px). expr_call catches this one separately and answers
"no such function", so only the offending call reconstructs and the
rest of the declaration still evaluates.