Diagnostic for metal ref mesh output assignment (#8365)

When slang detects assignment to a mesh output reference on metal,
generate a diagnostic message. (Metal mesh shader outputs must be
assigned via 'set' instead of 'ref'.)

Fixes #7498

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/diagnostics/metal-mesh-shader-output-ref.slang b/tests/diagnostics/metal-mesh-shader-output-ref.slang
new file mode 100644
index 000000000..45926b1f8
--- /dev/null
+++ b/tests/diagnostics/metal-mesh-shader-output-ref.slang
@@ -0,0 +1,22 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK):-target metal -entry meshMain
+
+struct VsOutput {
+  float4 pos : SV_Position;
+};
+
+[shader("mesh")]
+[numthreads(1, 1, 1)]
+[outputtopology("triangle")]
+void meshMain(out vertices VsOutput verts[3], out indices uint3 tris[1])
+{
+  SetMeshOutputCounts(3, 1);
+
+  // Output vertices
+  for (uint i = 0; i < 3; i++) {
+//CHECK: ([[# @LINE+1]]): error 56104
+    verts[i].pos = float4(0.0);
+  }
+
+  // Output indices
+  tris[0] = uint3(0, 1, 2);
+}