nir/algebraic: Detect missing f on F-strings

Missing f in other cases seems to be caught either elsewhere in the
script or by the C compiler.

Fixes: c49d6e0480 ("nir/algebraic: Elide range clamping of f2u sources")
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39031>

src/compiler/nir/nir_algebraic.py

@@ -114,6 +114,9 @@ class SearchExpression(object):
         self.sources = expr[1:]
         self.ignore_exact = False
 
+        assert '{' not in self.opcode, \
+            'Malformed opcode name \"{}\".'.format(self.opcode)
+
     @staticmethod
     def create(val):
         if isinstance(val, tuple):