HLSL: Allow empty struct initializers

Test/baseResults/hlsl.emptystruct.init.vert.out

+hlsl.emptystruct.init.vert
+WARNING: 0:3: 'Test_Empty' : variable with qualifier 'const' not initialized; zero initializing 
+
+Shader version: 500
+0:? Sequence
+0:6  Function Definition: @main(u1; ( temp 4-component vector of float)
+0:6    Function Parameters: 
+0:6      'vertexIndex' ( in uint)
+0:?     Sequence
+0:7      Branch: Return with expression
+0:7        Constant:
+0:7          0.000000
+0:7          0.000000
+0:7          0.000000
+0:7          0.000000
+0:6  Function Definition: main( ( temp void)
+0:6    Function Parameters: 
+0:?     Sequence
+0:6      move second child to first child ( temp uint)
+0:?         'vertexIndex' ( temp uint)
+0:?         'vertexIndex' (layout( location=0) in uint)
+0:6      move second child to first child ( temp 4-component vector of float)
+0:?         '@entryPointOutput' (layout( location=0) out 4-component vector of float)
+0:6        Function Call: @main(u1; ( temp 4-component vector of float)
+0:?           'vertexIndex' ( temp uint)
+0:?   Linker Objects
+0:?     'Test_Empty' ( const structure{})
+0:?     '@entryPointOutput' (layout( location=0) out 4-component vector of float)
+0:?     'vertexIndex' (layout( location=0) in uint)
+
+
+Linked vertex stage:
+
+
+Shader version: 500
+0:? Sequence
+0:6  Function Definition: @main(u1; ( temp 4-component vector of float)
+0:6    Function Parameters: 
+0:6      'vertexIndex' ( in uint)
+0:?     Sequence
+0:7      Branch: Return with expression
+0:7        Constant:
+0:7          0.000000
+0:7          0.000000
+0:7          0.000000
+0:7          0.000000
+0:6  Function Definition: main( ( temp void)
+0:6    Function Parameters: 
+0:?     Sequence
+0:6      move second child to first child ( temp uint)
+0:?         'vertexIndex' ( temp uint)
+0:?         'vertexIndex' (layout( location=0) in uint)
+0:6      move second child to first child ( temp 4-component vector of float)
+0:?         '@entryPointOutput' (layout( location=0) out 4-component vector of float)
+0:6        Function Call: @main(u1; ( temp 4-component vector of float)
+0:?           'vertexIndex' ( temp uint)
+0:?   Linker Objects
+0:?     'Test_Empty' ( const structure{})
+0:?     '@entryPointOutput' (layout( location=0) out 4-component vector of float)
+0:?     'vertexIndex' (layout( location=0) in uint)
+
+// Module Version 10000
+// Generated by (magic number): 80001
+// Id's are bound by 29
+
+                              Capability Shader
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint Vertex 4  "main" 20 23
+                              Source HLSL 500
+                              Name 4  "main"
+                              Name 12  "@main(u1;"
+                              Name 11  "vertexIndex"
+                              Name 18  "vertexIndex"
+                              Name 20  "vertexIndex"
+                              Name 23  "@entryPointOutput"
+                              Name 24  "param"
+                              Name 27  "Test"
+                              Decorate 20(vertexIndex) Location 0
+                              Decorate 23(@entryPointOutput) Location 0
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeInt 32 0
+               7:             TypePointer Function 6(int)
+               8:             TypeFloat 32
+               9:             TypeVector 8(float) 4
+              10:             TypeFunction 9(fvec4) 7(ptr)
+              14:    8(float) Constant 0
+              15:    9(fvec4) ConstantComposite 14 14 14 14
+              19:             TypePointer Input 6(int)
+ 20(vertexIndex):     19(ptr) Variable Input
+              22:             TypePointer Output 9(fvec4)
+23(@entryPointOutput):     22(ptr) Variable Output
+        27(Test):             TypeStruct
+              28:    27(Test) ConstantComposite
+         4(main):           2 Function None 3
+               5:             Label
+ 18(vertexIndex):      7(ptr) Variable Function
+       24(param):      7(ptr) Variable Function
+              21:      6(int) Load 20(vertexIndex)
+                              Store 18(vertexIndex) 21
+              25:      6(int) Load 18(vertexIndex)
+                              Store 24(param) 25
+              26:    9(fvec4) FunctionCall 12(@main(u1;) 24(param)
+                              Store 23(@entryPointOutput) 26
+                              Return
+                              FunctionEnd
+   12(@main(u1;):    9(fvec4) Function None 10
+ 11(vertexIndex):      7(ptr) FunctionParameter
+              13:             Label
+                              ReturnValue 15
+                              FunctionEnd

Test/hlsl.emptystruct.init.vert

+struct Test { };
+
+static const Test Test_Empty;
+
+float4 main(in uint vertexIndex : VERTEXID) : VS_OUT_POSITION
+{
+    return 0;
+}

glslang/MachineIndependent/parseConst.cpp

@@ -76,12 +76,6 @@ bool TConstTraverser::visitAggregate(TVisit /* visit */, TIntermAggregate* node)
         return false;
     }
 
-    if (node->getSequence().size() == 0) {
-        error = true;
-
-        return false;
-    }
-
     bool flag = node->getSequence().size() == 1 && node->getSequence()[0]->getAsTyped()->getAsConstantUnion();
     if (flag) {
         singleConstantParam = true;

gtests/Hlsl.FromFile.cpp

@@ -106,6 +106,7 @@ INSTANTIATE_TEST_CASE_P(
         {"hlsl.doLoop.frag", "PixelShaderFunction"},
         {"hlsl.emptystructreturn.frag", "main"},
         {"hlsl.emptystructreturn.vert", "main"},
+        {"hlsl.emptystruct.init.vert", "main"},
         {"hlsl.entry-in.frag", "PixelShaderFunction"},
         {"hlsl.entry-out.frag", "PixelShaderFunction"},
         {"hlsl.float1.frag", "PixelShaderFunction"},