Disallow identifier names that overlap existing types.

It's not legal to use identifiers like "int" or "sampler" to name your
variables (or enums, or structs, etc.). SkSL will now report this as an
error instead of relying on the driver to catch this.

(Note that in some contexts, it might be legal by the spec to reuse a
name that you introduced yourself, depending on the scope. In practice,
this confuses Apple GLSL, so we shouldn't support it anyway.)

This caught several existing places in our code where we used the name
"sampler." These were never exposed to the driver (they were intrinsics
that we would replace during compilation) so they were harmless before.

Change-Id: Ia6dcfca8c500d02e1eb5f9427bed8727e114dfc2
Bug: skia:11036
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/340758
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
24 files changed