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")

src/compiler/nir/nir_algebraic.py

@@ -107,6 +107,9 @@ 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):