glsl: Improve error message when read-only vars are written

Improves the cases when:
* an explicit assignment references the read-only variable
* an 'out' or 'inout' function parameter references the read-only variable

1 files changed, 8 insertions, 1 deletions

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index dfb016cf7d..1bca3ecf12 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -639,7 +639,14 @@ do_assignment(exec_list *instructions, struct _mesa_glsl_parse_state *state,
    bool error_emitted = (lhs->type->is_error() || rhs->type->is_error());
 
    if (!error_emitted) {
-      if (!lhs->is_lvalue()) {
+      if (lhs->variable_referenced() != NULL
+          && lhs->variable_referenced()->read_only) {
+         _mesa_glsl_error(&lhs_loc, state,
+                          "assignment to read-only variable '%s'",
+                          lhs->variable_referenced()->name);
+         error_emitted = true;
+
+      } else if (!lhs->is_lvalue()) {
 	 _mesa_glsl_error(& lhs_loc, state, "non-lvalue in assignment");
 	 error_emitted = true;
       }