[Capability System] Fix bug where capabilities do not correctly propegate if AST-parent has target+set the AST-child does not (#8175)

Fixes: #8174

Changes:
* To determine if we propagate capabilities, we need to ensure that a
`join` will do nothing (optimization since `join` is expensive + caching
data for the `join` adds up to be expensive). This logic was changed in
`slang-check-decl.cpp` since the current logic was incorrect.
* A parent could have the set `metal+glsl` and the use-site could have
`glsl`. In this case, we will not remove `metal` from the parent since
`{metal+glsl}.implies({glsl})` is true.

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

2 files changed, 30 insertions, 2 deletions

diff --git a/tests/glsl-intrinsic/shader-subgroup/shader-subgroup-arithmetic_Inclusive.slang b/tests/glsl-intrinsic/shader-subgroup/shader-subgroup-arithmetic_Inclusive.slang
index 40f77ee61..b9f26ca30 100644
--- a/tests/glsl-intrinsic/shader-subgroup/shader-subgroup-arithmetic_Inclusive.slang
+++ b/tests/glsl-intrinsic/shader-subgroup/shader-subgroup-arithmetic_Inclusive.slang
@@ -17,9 +17,11 @@
 
 #if 1                        \
     && !defined(TARGET_HLSL) \
-    && !defined(TARGET_CUDA)
+    && !defined(TARGET_CUDA) \
+    && !defined(WGPU)        \
+    && !defined(METAL)
 // hlsl does not treat boolean types with subgroup.* as a logical operator
-// cuda is missing an implementation
+// cuda, wgsl, and metal is missing an implementation
 #define TEST_when_logical_operators_are_implemented
 #endif
 
diff --git a/tests/language-feature/capability/capability8.slang b/tests/language-feature/capability/capability8.slang
new file mode 100644
index 000000000..2907166e0
--- /dev/null
+++ b/tests/language-feature/capability/capability8.slang
@@ -0,0 +1,26 @@
+//TEST:SIMPLE(filecheck=CHECK-PASS): -target glsl -entry computeMain -stage compute -profile sm_5_0
+//TEST:SIMPLE(filecheck=CHECK): -target metal -entry computeMain -stage compute -profile sm_5_0
+
+// Test that we diagnose an error when calling a method that requires a capability that is not
+// available in the target.
+
+RWStructuredBuffer<int> outputBuffer;
+
+[require(cpp_cuda_glsl_hlsl_metal_spirv_wgsl, byteaddressbuffer)]
+struct Test
+{
+    [require(cpp_cuda_glsl_hlsl_spirv_wgsl, structuredbuffer)]
+    int data()
+    {
+        return 0;
+    }
+}
+
+// CHECK-PASS-NOT: error 36107
+// CHECK: ([[# @LINE+1]]): error 36107{{.*}}metal
+void computeMain()
+{
+    Test t;
+    // CHECK: ([[# @LINE+1]]): note: see using of 'data'
+    outputBuffer[0] = t.data();
+}
\ No newline at end of file