Add Sampler*Shadow type aliases. (#5789)

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

Author: csyonghe

source/slang/hlsl.meta.slang

@@ -4052,6 +4052,20 @@ ${{{{
 }
 }}}}
 
+// Declare Sampler*Shadow type aliases.
+${{{{
+    for (int shape = 0; shape < 4; shape++)
+    for (int isArray = 0; isArray<=1; isArray++)
+    {
+}}}}
+/// Represents a handle to a $(shapeTypeNames[shape]) combined texture-sampler for shadow comparison.
+/// @param format The storage format of the texture.
+/// @see Please refer to `_Texture` for more information about texture types.
+/// @category texture_types
+typealias Sampler$(shapeTypeNames[shape])$(arrayPostFix[isArray])Shadow<int format=0> = _Texture<float, __Shape$(shapeTypeNames[shape]), $(isArray), 0, 0, 0, 1, 1, format>;
+${{{{
+    }
+}}}}
 
 // Atomic intrinsic insts.
 

tests/spirv/sampler-shadow.slang

@@ -0,0 +1,13 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+// CHECK: OpImageSampleDrefExplicitLod
+
+Sampler2DShadow ss;
+
+RWStructuredBuffer<float> output;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    output[0] = ss.SampleCmpLevelZero(float2(0.0), 0.5);
+}