ShaderLab: #define macro not expanded after dot (swizzle position)

[GuoLei1990]

Description

ShaderLab compiler does not expand #define macros used after . (dot) in swizzle positions.

Reproduction

#define OCCLUSION_CHANNEL r
#define ROUGHNESS_CHANNEL g
#define METALLIC_CHANNEL b

vec4 pbrRes = texture2D(pbrMap, uv);
pbr.x *= pbrRes.OCCLUSION_CHANNEL;  // Expected: pbrRes.r, actual: compile error
pbr.y *= pbrRes.ROUGHNESS_CHANNEL;
pbr.z *= pbrRes.METALLIC_CHANNEL;

Error

CompilationError: Unexpected token OCCLUSION_CHANNEL
|··· pbr.x *= pbrRes.OCCLUSION_CHANNEL; ^^^^^^^^^^^^^^^^^

Expected

Standard GLSL preprocessors expand macros before parsing, so pbrRes.OCCLUSION_CHANNEL should be expanded to pbrRes.r and compile normally. This is a common pattern in Cocos Creator shaders.

Workaround

Inline the swizzle directly: pbrRes.r instead of pbrRes.OCCLUSION_CHANNEL.