[Mesa-dev] [PATCH] glsl: emit a specific error when ast_*_assign changes type

[Ilia Mirkin]

For regular ast_add, we can implicitly change either a or b's type.
However in an assignment situation, the type of the lvalue is fixed. So
if the implicit conversion logic decides to change it, it means that the
rhs's type could not be converted to the lhs type.

Emit a specific error for this rather than the rather mysterious "is not
an lvalue" error that results from having a i2f or other operation as
the lvalue.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96729
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/compiler/glsl/ast_to_hir.cpp | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index 8ddc084..55ee840 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -1353,7 +1353,7 @@ ast_expression::do_hir(exec_list *instructions,
    };
    ir_rvalue *result = NULL;
    ir_rvalue *op[3];
-   const struct glsl_type *type; /* a temporary variable for switch cases */
+   const struct glsl_type *type, *orig_type;
    bool error_emitted = false;
    YYLTYPE loc;
 
@@ -1639,10 +1639,18 @@ ast_expression::do_hir(exec_list *instructions,
       op[0] = this->subexpressions[0]->hir(instructions, state);
       op[1] = this->subexpressions[1]->hir(instructions, state);
 
+      orig_type = op[0]->type;
       type = arithmetic_result_type(op[0], op[1],
                                     (this->oper == ast_mul_assign),
                                     state, & loc);
 
+      if (type != orig_type) {
+         _mesa_glsl_error(& loc, state,
+                          "could not implicitly convert "
+                          "rvalue type to lvalue type");
+         type = glsl_type::error_type;
+      }
+
       ir_rvalue *temp_rhs = new(ctx) ir_expression(operations[this->oper], type,
                                                    op[0], op[1]);
 
@@ -1666,8 +1674,16 @@ ast_expression::do_hir(exec_list *instructions,
       op[0] = this->subexpressions[0]->hir(instructions, state);
       op[1] = this->subexpressions[1]->hir(instructions, state);
 
+      orig_type = op[0]->type;
       type = modulus_result_type(op[0], op[1], state, &loc);
 
+      if (type != orig_type) {
+         _mesa_glsl_error(& loc, state,
+                          "could not implicitly convert "
+                          "rvalue type to lvalue type");
+         type = glsl_type::error_type;
+      }
+
       assert(operations[this->oper] == ir_binop_mod);
 
       ir_rvalue *temp_rhs;
@@ -1707,7 +1723,17 @@ ast_expression::do_hir(exec_list *instructions,
       this->subexpressions[0]->set_is_lhs(true);
       op[0] = this->subexpressions[0]->hir(instructions, state);
       op[1] = this->subexpressions[1]->hir(instructions, state);
+
+      orig_type = op[0]->type;
       type = bit_logic_result_type(op[0], op[1], this->oper, state, &loc);
+
+      if (type != orig_type) {
+         _mesa_glsl_error(& loc, state,
+                          "could not implicitly convert "
+                          "rvalue type to lvalue type");
+         type = glsl_type::error_type;
+      }
+
       ir_rvalue *temp_rhs = new(ctx) ir_expression(operations[this->oper],
                                                    type, op[0], op[1]);
       error_emitted =
-- 
2.7.3