Add warning for ignored binding attributes on uniforms (#6373)

Fixes #4251

When binding attributes (like [[vk::binding]]) are specified on uniforms
that get packed into the default constant buffer, these binding
attributes are effectively ignored since the uniform will always be
placed at descriptor set 0, binding 0. This can be confusing for users
who expect their explicit bindings to take effect.

This change adds a new warning (71) that informs users when their
binding attributes on uniforms will be ignored, and suggests declaring
the uniform inside a constant buffer to preserve the explicit binding.

The warning helps users understand:
1. Why their binding attribute isn't having the expected effect
2. That the uniform is being packed into the default constant buffer
3. How to fix it by using a constant buffer declaration

Added test case in tests/bugs/binding-attribute-ignored.slang to verify
the warning behavior.

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/bugs/binding-attribute-ignored.slang b/tests/bugs/binding-attribute-ignored.slang
new file mode 100644
index 000000000..9025489ec
--- /dev/null
+++ b/tests/bugs/binding-attribute-ignored.slang
@@ -0,0 +1,22 @@
+// binding-attribute-ignored.slang
+// Test that binding attributes on uniforms that get packed into the default uniform buffer trigger a warning
+
+//TEST:SIMPLE(filecheck=CHECK):-target spirv
+
+//CHECK: ([[# @LINE+2]]): warning 39071
+[[vk::binding(1, 2)]]
+uniform float4 g_position;
+
+//CHECK: ([[# @LINE+2]]): warning 39071
+[[vk::binding(3, 1)]]
+uniform float4x4 g_transform;
+
+// This won't trigger a warning because it's a texture (not packed into default uniform buffer)
+[[vk::binding(0, 0)]]
+Texture2D g_texture;
+
+[shader("vertex")]
+float4 main(float4 pos : POSITION) : SV_POSITION
+{
+    return g_position;
+} 
\ No newline at end of file