[Bug 56465] New: d3dcompiler fails to compile shader functions that have optional arguments ("E5000: syntax error, unexpected '=', expecting ')'")

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=56465

Bug ID: 56465
           Summary: d3dcompiler fails to compile shader functions that
                    have optional arguments ("E5000: syntax error,
                    unexpected '=', expecting ')'")
           Product: vkd3d
           Version: 1.11
          Hardware: x86-64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: hlsl
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Minimal example (compile with `i686-w64-mingw32-cc *.c -ld3dx9_36`):

#include <windows.h>
#include <d3dx9shader.h>
#include <stdio.h>

int main()
{
    static const char src[] = "float4 main(float4 color : COLOR =
float4(0,0,0,0)) : COLOR { return color; }";
    ID3DXBuffer *out = NULL;
    HRESULT res = D3DXCompileShader(src, sizeof(src), NULL, NULL, "main",
"ps_2_0", 0, &out, NULL, NULL);
    printf("res=%x\n", res);
    return res;
}

Output:

0024:err:d3dcompiler:D3DCompile2 Failed to compile shader, vkd3d result -4.
0024:err:d3dcompiler:D3DCompile2 Shader log:
0024:err:d3dcompiler:D3DCompile2     <anonymous>:1:36: E5000: syntax error,
unexpected '=', expecting ')'
0024:err:d3dcompiler:D3DCompile2 
res=80004005

Output after `winetricks d3dcompiler_47`:

res=0