Expose translator issues with struct samplers.

Struct samplers assert in the Vulkan and Metal backends during
rewriting. Add a test - skipped for now on these backends - to
highlight this issue.

Bug: angleproject:6641
Change-Id: I95cbc9e5f4122f1ac7db926ac44c4cccc1b6f87a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3256235
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>

src/tests/angle_end2end_tests_expectations.txt

@@ -25,6 +25,10 @@
 4889 VULKAN : GeometryShaderTest.LayeredFramebufferPreRenderClear3DColor/* = SKIP
 4889 VULKAN : GLSLTest_ES31.VaryingTessellationSampleInAndOut/* = SKIP
 
+// Vulkan generic
+6641 VULKAN : UniformTest.UnusedStructInlineUniform/* = SKIP
+6641 VULKAN : UniformTest.UnusedStructInlineUniformWithSampler/* = SKIP
+
 // Windows
 3786 WIN NVIDIA D3D11 : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
 4092 WIN VULKAN : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
@@ -108,6 +112,8 @@
 6570 MAC INTEL OPENGL : WebGLCompatibilityTest.RGB32FTextures/* = SKIP
 6603 MAC OPENGL : ProgramBinaryES3Test.SaveAndLoadDetachedShaders/* = SKIP
 6643 MAC AMD OPENGL : TransformFeedbackTest.TransformFeedbackQueryPausedDrawThenResume/* = SKIP
+6641 MAC METAL : UniformTest.UnusedStructInlineUniform/* = SKIP
+6641 MAC METAL : UniformTest.UnusedStructInlineUniformWithSampler/* = SKIP
 
 // Failures from Transform Feedback Enablement. Passes on BigSur
 6407 MAC NVIDIA METAL : TransformFeedbackTest.OptimizedVaryings/ES3_Metal = SKIP

src/tests/gl_tests/UniformTest.cpp

@@ -1461,6 +1461,58 @@ void main()
     EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
 }
 
+TEST_P(UniformTest, UnusedStructInlineUniform)
+{
+    constexpr char kVS[] = R"(precision highp float;
+attribute vec4 position;
+void main()
+{
+    gl_Position = position;
+})";
+
+    constexpr char kFS[] = R"(precision highp float;
+uniform struct {
+  vec3  aVec3;
+  vec2 aVec2;
+}aUniform;
+varying vec2 texcoord;
+void main()
+{
+    gl_FragColor = vec4(0,1,0,1);
+})";
+
+    mProgram = CompileProgram(kVS, kFS);
+    ASSERT_NE(mProgram, 0u);
+    drawQuad(mProgram, "position", 0.5f);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
+TEST_P(UniformTest, UnusedStructInlineUniformWithSampler)
+{
+    constexpr char kVS[] = R"(precision highp float;
+attribute vec4 position;
+void main()
+{
+    gl_Position = position;
+})";
+
+    constexpr char kFS[] = R"(precision highp float;
+uniform struct {
+  sampler2D  aSampler;
+  vec3 aVec3;
+}aUniform;
+varying vec2 texcoord;
+void main()
+{
+    gl_FragColor = vec4(0,1,0,1);
+})";
+
+    mProgram = CompileProgram(kVS, kFS);
+    ASSERT_NE(mProgram, 0u);
+    drawQuad(mProgram, "position", 0.5f);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these
 // tests should be run against.
 ANGLE_INSTANTIATE_TEST_ES2_AND_ES3(SimpleUniformTest);