Fix compound assignment precision emulation

src/compiler/translator/EmulatePrecision.cpp

@@ -157,7 +157,7 @@ void RoundingHelperWriter::writeCompoundAssignmentHelper(TInfoSinkBase &sink,
         "}\n";
     sink <<
         lTypeStr << " angle_compound_" << opNameStr << "_frl(inout " << lTypeStr << " x, in " << rTypeStr << " y) {\n"
-        "    x = angle_frl(angle_frm(x) " << opStr << " y);\n"
+        "    x = angle_frl(angle_frl(x) " << opStr << " y);\n"
         "    return x;\n"
         "}\n";
     // clang-format on
@@ -464,7 +464,7 @@ TIntermAggregate *createCompoundAssignmentFunctionCallNode(TIntermTyped *left,
     TIntermSequence *arguments = new TIntermSequence();
     arguments->push_back(left);
     arguments->push_back(right);
-    return createInternalFunctionCallNode(TType(EbtVoid), functionName, arguments);
+    return createInternalFunctionCallNode(left->getType(), functionName, arguments);
 }
 
 bool ParentUsesResult(TIntermNode *parent, TIntermTyped *node)

src/tests/compiler_tests/DebugShaderPrecision_test.cpp

@@ -1042,3 +1042,20 @@ TEST(DebugShaderPrecisionNegativeTest, HLSL3Unsupported)
                                    shaderString, &resources, 0, &translatedCode, &infoLog));
 }
 #endif  // defined(ANGLE_ENABLE_HLSL)
+
+// Test that compound assignment inside an expression compiles correctly. This is a test for a bug
+// where incorrect type information on the compound assignment call node caused an assert to trigger
+// in the debug build.
+TEST_F(DebugShaderPrecisionTest, CompoundAssignmentInsideExpression)
+{
+    const std::string &shaderString =
+        "#version 300 es\n"
+        "precision mediump float;\n"
+        "out vec4 my_FragColor;\n"
+        "void main() {\n"
+        "   float f = 0.0;\n"
+        "   my_FragColor = vec4(abs(f += 1.0), 0, 0, 1);\n"
+        "}\n";
+    compile(shaderString);
+    ASSERT_TRUE(foundInAllGLSLCode("abs(angle_compound_add_frm(f, 1.0))"));
+}