Disallow layout+invariant combo on ESSL 3.00 variable declarations

src/compiler/translator/QualifierTypes.cpp

@@ -135,6 +135,16 @@ bool HasRepeatingQualifiers(const TTypeQualifierBuilder::QualifierSequence &qual
                     *errorMessage = "The layout qualifier specified multiple times.";
                     return true;
                 }
+                if (invariantFound && !areQualifierChecksRelaxed)
+                {
+                    // This combination is not correct according to the syntax specified in the
+                    // formal grammar in the ESSL 3.00 spec. In ESSL 3.10 the grammar does not have
+                    // a similar restriction.
+                    *errorMessage =
+                        "The layout qualifier and invariant qualifier cannot coexist in the same "
+                        "declaration according to the grammar.";
+                    return true;
+                }
                 layoutFound = true;
                 const TLayoutQualifier &currentQualifier =
                     static_cast<const TLayoutQualifierWrapper *>(qualifiers[i])->getQualifier();

src/tests/compiler_tests/MalformedShader_test.cpp

@@ -2516,3 +2516,20 @@ TEST_F(MalformedShaderTest, InvariantDeclarationWithLayoutQualifier)
         FAIL() << "Shader compilation succeeded, expecting failure " << mInfoLog;
     }
 }
+
+// Variable declaration with both invariant and layout qualifiers is not valid in the formal grammar
+// provided in the ESSL 3.00 spec. ESSL 3.10 starts allowing this combination, but ESSL 3.00 should
+// still disallow it.
+TEST_F(MalformedShaderTest, VariableDeclarationWithInvariantAndLayoutQualifierESSL300)
+{
+    const std::string &shaderString =
+        "#version 300 es\n"
+        "precision mediump float;\n"
+        "invariant layout(location = 0) out vec4 my_FragColor;\n"
+        "void main() {\n"
+        "}\n";
+    if (compile(shaderString))
+    {
+        FAIL() << "Shader compilation succeeded, expecting failure " << mInfoLog;
+    }
+}