re-land of skslc type constructor cleanups

BUG=skia:

Change-Id: I953be07e2389dd4a9e7dcce0ddfd7505b309bda1
Reviewed-on: https://skia-review.googlesource.com/8265
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/sksl/README b/src/sksl/README
index d78953f595..98103fa64f 100644
--- a/src/sksl/README
+++ b/src/sksl/README
@@ -41,6 +41,9 @@ following differences between SkSL and GLSL:
   have to be expressed "vec2(x, y) * 4.0". There is no performance penalty for 
   this, as the number is converted to a float at compile time)
 * type suffixes on numbers (1.0f, 0xFFu) are both unnecessary and unsupported
+* creating a smaller vector from a larger vector (e.g. vec2(vec3(1))) is
+  intentionally disallowed, as it is just a wordier way of performing a swizzle.
+  Use swizzles instead.
 * Use texture() instead of textureProj(), e.g. texture(sampler2D, vec3) is
   equivalent to GLSL's textureProj(sampler2D, vec3)
 * some built-in functions and one or two rarely-used language features are not