Error: not a swizzle with custom struct

[Johannes Rössel [yWorks]]

For the following code:

struct S{
  vec2 p1;
  vec2 cp1;
  vec2 cp2;
  vec2 p2;
};

vec2 calc(S points, float t) {
  vec4 m1m2 = mix(vec4(points.p1, points.cp1), vec4(points.cp1, points.cp2), t);
  return m1m2.xy;
}

and the following options:

--format indented --preserve-all-globals --preserve-externals --no-sequence --no-remove-unused

I get an error

not a swizzle (c)

This was a bit hard to find, as it happened somewhere in a larger shader snippet (location information for errors would be great!). It appears as if swizzleIndex is called with the right-hand side of points, even though this should have been guarded by isFieldSwizzle.

Oh, wait, it might not be in dropLastSwizzle.

[Laurent Le Brun]

Thanks for the report, this should be easy to fix.

dropLastSwizzle is missing a check for isFieldSwizzle.

[Johannes Rössel [yWorks]]

Perhaps moving that check to renameField is a bit safer in the long run. I'd attempt a fix here, but I think the total amount of F# code I've ever written amounts to perhaps 100 lines or so, without much understanding.