glsl: disallow implicit conversions in ESSL shaders

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/glsl/ast_to_hir.cpp

@@ -291,6 +291,10 @@ apply_implicit_conversion(const glsl_type *to, ir_rvalue * &from,
    if (!state->is_version(120, 0))
       return false;
 
+   /* ESSL does not allow implicit conversions */
+   if (state->es_shader)
+      return false;
+
    /* From page 27 (page 33 of the PDF) of the GLSL 1.50 spec:
     *
     *    "There are no implicit array or structure conversions. For

src/compiler/glsl_types.cpp

@@ -1139,6 +1139,13 @@ glsl_type::can_implicitly_convert_to(const glsl_type *desired,
    if (this == desired)
       return true;
 
+   /* ESSL does not allow implicit conversions. If there is no state, we're
+    * doing intra-stage function linking where these checks have already been
+    * done.
+    */
+   if (state && state->es_shader)
+      return false;
+
    /* There is no conversion among matrix types. */
    if (this->matrix_columns > 1 || desired->matrix_columns > 1)
       return false;