Add a forward reference function call test.

Test/forwardRef.frag

+uniform vec4 bigColor;
+varying vec4 BaseColor;
+uniform float d;
+
+void bar();
+float foo(vec4);
+float unreachableReturn();
+
+void main()
+{
+    vec4 color = vec4(foo(BaseColor));
+
+    bar();
+    float f = unreachableReturn();
+    
+    gl_FragColor = color * f;
+}
+
+void bar()
+{
+}
+
+float unreachableReturn()
+{
+    bar();
+    if (d < 4.2)
+        return 1.2;
+    else
+        return 4.5;
+}
+
+float foo(vec4 bar)
+{
+    return bar.x + bar.y;
+}

Test/testlist

@@ -28,3 +28,4 @@ comment.frag
 constErrors.frag
 constFold.frag
 errors.frag
+forwardRef.frag