Fix uses of dynamic_cast on types in reflection API (#731)

The `Type` infrastructure uses a class hierarchy, but blindly `dynamic_cast`ing to a desired case doesn't always give the expected result, because a `Type` could represent a `typedef` (a `NamedExpressionType`) that itself resolves to, e.g, a vector type (a `VectorExpressionType`). In that case a `dynamic_cast<VectorExpressionType*>(someType)` would fail, even though the type logically represents a vector. The `Type::As<T>()` method is designed to handle this case, by "looking through" simple `typedef`s to get at the real definition of a type.

The fix in this case is to use `Type::As<T>()` at various points in the reflection code (`reflection.cpp`) instead of `dynamic_cast`.

This problem surfaced with a `StructuredBuffer<float2>` not reflecting correctly, because the element type (`float2`) is actually a `typedef` (for `vector<float,2>`), so I've included a test case that stresses that case. Getting the right output in the test required tweaking the `slang-reflection-test` tool to produce additional output for resource types (currently narrowed down to only affect structured buffers to avoid large diffs in expected test outputs).

6 files changed, 146 insertions, 19 deletions

diff --git a/source/slang/reflection.cpp b/source/slang/reflection.cpp
index 73b616377..44920fb9f 100644
--- a/source/slang/reflection.cpp
+++ b/source/slang/reflection.cpp
@@ -189,7 +189,7 @@ SLANG_API unsigned int spReflectionType_GetFieldCount(SlangReflectionType* inTyp
 
     // TODO: maybe filter based on kind
 
-    if(auto declRefType = dynamic_cast<DeclRefType*>(type))
+    if(auto declRefType = type->As<DeclRefType>())
     {
         auto declRef = declRefType->declRef;
         if( auto structDeclRef = declRef.As<StructDecl>())
@@ -208,7 +208,7 @@ SLANG_API SlangReflectionVariable* spReflectionType_GetFieldByIndex(SlangReflect
 
     // TODO: maybe filter based on kind
 
-    if(auto declRefType = dynamic_cast<DeclRefType*>(type))
+    if(auto declRefType = type->As<DeclRefType>())
     {
         auto declRef = declRefType->declRef;
         if( auto structDeclRef = declRef.As<StructDecl>())
@@ -226,11 +226,11 @@ SLANG_API size_t spReflectionType_GetElementCount(SlangReflectionType* inType)
     auto type = convert(inType);
     if(!type) return 0;
 
-    if(auto arrayType = dynamic_cast<ArrayExpressionType*>(type))
+    if(auto arrayType = type->As<ArrayExpressionType>())
     {
         return arrayType->ArrayLength ? (size_t) GetIntVal(arrayType->ArrayLength) : 0;
     }
-    else if( auto vectorType = dynamic_cast<VectorExpressionType*>(type))
+    else if( auto vectorType = type->As<VectorExpressionType>())
     {
         return (size_t) GetIntVal(vectorType->elementCount);
     }
@@ -243,19 +243,19 @@ SLANG_API SlangReflectionType* spReflectionType_GetElementType(SlangReflectionTy
     auto type = convert(inType);
     if(!type) return nullptr;
 
-    if(auto arrayType = dynamic_cast<ArrayExpressionType*>(type))
+    if(auto arrayType = type->As<ArrayExpressionType>())
     {
         return (SlangReflectionType*) arrayType->baseType.Ptr();
     }
-    else if( auto constantBufferType = dynamic_cast<ConstantBufferType*>(type))
+    else if( auto constantBufferType = type->As<ConstantBufferType>())
     {
         return convert(constantBufferType->elementType.Ptr());
     }
-    else if( auto vectorType = dynamic_cast<VectorExpressionType*>(type))
+    else if( auto vectorType = type->As<VectorExpressionType>())
     {
         return convert(vectorType->elementType.Ptr());
     }
-    else if( auto matrixType = dynamic_cast<MatrixExpressionType*>(type))
+    else if( auto matrixType = type->As<MatrixExpressionType>())
     {
         return convert(matrixType->getElementType());
     }
@@ -268,15 +268,15 @@ SLANG_API unsigned int spReflectionType_GetRowCount(SlangReflectionType* inType)
     auto type = convert(inType);
     if(!type) return 0;
 
-    if(auto matrixType = dynamic_cast<MatrixExpressionType*>(type))
+    if(auto matrixType = type->As<MatrixExpressionType>())
     {
         return (unsigned int) GetIntVal(matrixType->getRowCount());
     }
-    else if(auto vectorType = dynamic_cast<VectorExpressionType*>(type))
+    else if(auto vectorType = type->As<VectorExpressionType>())
     {
         return 1;
     }
-    else if( auto basicType = dynamic_cast<BasicExpressionType*>(type) )
+    else if( auto basicType = type->As<BasicExpressionType>() )
     {
         return 1;
     }
@@ -289,15 +289,15 @@ SLANG_API unsigned int spReflectionType_GetColumnCount(SlangReflectionType* inTy
     auto type = convert(inType);
     if(!type) return 0;
 
-    if(auto matrixType = dynamic_cast<MatrixExpressionType*>(type))
+    if(auto matrixType = type->As<MatrixExpressionType>())
     {
         return (unsigned int) GetIntVal(matrixType->getColumnCount());
     }
-    else if(auto vectorType = dynamic_cast<VectorExpressionType*>(type))
+    else if(auto vectorType = type->As<VectorExpressionType>())
     {
         return (unsigned int) GetIntVal(vectorType->elementCount);
     }
-    else if( auto basicType = dynamic_cast<BasicExpressionType*>(type) )
+    else if( auto basicType = type->As<BasicExpressionType>() )
     {
         return 1;
     }
@@ -310,16 +310,16 @@ SLANG_API SlangScalarType spReflectionType_GetScalarType(SlangReflectionType* in
     auto type = convert(inType);
     if(!type) return 0;
 
-    if(auto matrixType = dynamic_cast<MatrixExpressionType*>(type))
+    if(auto matrixType = type->As<MatrixExpressionType>())
     {
         type = matrixType->getElementType();
     }
-    else if(auto vectorType = dynamic_cast<VectorExpressionType*>(type))
+    else if(auto vectorType = type->As<VectorExpressionType>())
     {
         type = vectorType->elementType.Ptr();
     }
 
-    if(auto basicType = dynamic_cast<BasicExpressionType*>(type))
+    if(auto basicType = type->As<BasicExpressionType>())
     {
         switch (basicType->baseType)
         {
diff --git a/tests/reflection/structured-buffer.slang b/tests/reflection/structured-buffer.slang
new file mode 100644
index 000000000..491d61486
--- /dev/null
+++ b/tests/reflection/structured-buffer.slang
@@ -0,0 +1,19 @@
+//TEST:REFLECTION:-profile ps_4_0 -target hlsl
+
+// Confirm that we reflect the contents of structure-buffer types correctly.
+
+struct S
+{
+	float2 a;
+	float  b;
+	uint   c;
+};
+
+StructuredBuffer<uint> x;
+StructuredBuffer<float2> y;
+StructuredBuffer<S> z;
+
+float4 main() : SV_Target
+{
+    return x[0] + y[0].xyxy + z[0].a.xyxy;
+}
\ No newline at end of file
diff --git a/tests/reflection/structured-buffer.slang.expected b/tests/reflection/structured-buffer.slang.expected
new file mode 100644
index 000000000..70ceb64f2
--- /dev/null
+++ b/tests/reflection/structured-buffer.slang.expected
@@ -0,0 +1,75 @@
+result code = 0
+standard error = {
+}
+standard output = {
+{
+    "parameters": [
+        {
+            "name": "x",
+            "binding": {"kind": "shaderResource", "index": 0},
+            "type": {
+                "kind": "resource",
+                "baseShape": "structuredBuffer",
+                "resultType": {
+                    "kind": "scalar",
+                    "scalarType": "uint32"
+                }
+            }
+        },
+        {
+            "name": "y",
+            "binding": {"kind": "shaderResource", "index": 1},
+            "type": {
+                "kind": "resource",
+                "baseShape": "structuredBuffer",
+                "resultType": {
+                    "kind": "vector",
+                    "elementCount": 2,
+                    "elementType": {
+                        "kind": "scalar",
+                        "scalarType": "float32"
+                    }
+                }
+            }
+        },
+        {
+            "name": "z",
+            "binding": {"kind": "shaderResource", "index": 2},
+            "type": {
+                "kind": "resource",
+                "baseShape": "structuredBuffer",
+                "resultType": {
+                    "kind": "struct",
+                    "fields": [
+                        "name": "a",
+                        "type": {
+                            "kind": "vector",
+                            "elementCount": 2,
+                            "elementType": {
+                                "kind": "scalar",
+                                "scalarType": "float32"
+                            }
+                        },
+                        "name": "b",
+                        "type": {
+                            "kind": "scalar",
+                            "scalarType": "float32"
+                        },
+                        "name": "c",
+                        "type": {
+                            "kind": "scalar",
+                            "scalarType": "uint32"
+                        }
+                    ]
+                }
+            }
+        }
+    ],
+    "entryPoints": [
+        {
+            "name": "main",
+            "stage:": "fragment"
+        }
+    ]
+}
+}
diff --git a/tests/reflection/thread-group-size.hlsl.expected b/tests/reflection/thread-group-size.hlsl.expected
index cd5d09e35..46b0eb87e 100644
--- a/tests/reflection/thread-group-size.hlsl.expected
+++ b/tests/reflection/thread-group-size.hlsl.expected
@@ -10,7 +10,11 @@ standard output = {
             "type": {
                 "kind": "resource",
                 "baseShape": "structuredBuffer",
-                "access": "readWrite"
+                "access": "readWrite",
+                "resultType": {
+                    "kind": "scalar",
+                    "scalarType": "float32"
+                }
             }
         }
     ],
diff --git a/tests/reflection/unbounded-arrays.hlsl.1.expected b/tests/reflection/unbounded-arrays.hlsl.1.expected
index 382fc25bc..60d894ba7 100644
--- a/tests/reflection/unbounded-arrays.hlsl.1.expected
+++ b/tests/reflection/unbounded-arrays.hlsl.1.expected
@@ -98,7 +98,15 @@ standard output = {
             "type": {
                 "kind": "resource",
                 "baseShape": "structuredBuffer",
-                "access": "readWrite"
+                "access": "readWrite",
+                "resultType": {
+                    "kind": "vector",
+                    "elementCount": 4,
+                    "elementType": {
+                        "kind": "scalar",
+                        "scalarType": "float32"
+                    }
+                }
             }
         }
     ],
diff --git a/tools/slang-reflection-test/main.cpp b/tools/slang-reflection-test/main.cpp
index 7e5f268f3..872d2ff3a 100644
--- a/tools/slang-reflection-test/main.cpp
+++ b/tools/slang-reflection-test/main.cpp
@@ -372,6 +372,27 @@ static void emitReflectionTypeInfoJSON(
                 }
                 write(writer, "\"");
             }
+
+            // TODO: We should really print the result type for all resource
+            // types, but current test output depends on the old behavior, so
+            // we only add result type output for structured buffers at first.
+            //
+            switch (shape & SLANG_RESOURCE_BASE_SHAPE_MASK)
+            {
+            default:
+                break;
+
+            case SLANG_STRUCTURED_BUFFER:
+                if( auto resultType = type->getResourceResultType() )
+                {
+                    write(writer, ",\n");
+                    write(writer, "\"resultType\": ");
+                    emitReflectionTypeJSON(
+                        writer,
+                        resultType);
+                }
+                break;
+            }
         }
         break;