use make_bytelike. minor refactor to be a classmethod

vyper/builtins/functions.py

@@ -2296,15 +2296,9 @@ def build_IR(self, expr, args, kwargs, context):
 
             schema = args_abi_t.selector_name().encode("utf-8")
             schema_t = StringT(len(schema))
-            schema_buf = context.new_internal_variable(schema_t)
+            schema_buf = Expr._make_bytelike(context, StringT, schema)
 
             ret = ["seq"]
-            ret.append(["mstore", schema_buf, len(schema)])
-
-            # TODO use Expr.make_bytelike, or better have a `bytestring` IRnode type
-            ret.append(
-                ["mstore", add_ofst(schema_buf, 32), bytes_to_int(schema.ljust(32, b"\x00"))]
-            )
 
             payload_buflen = args_abi_t.size_bound()
             payload_t = BytesT(payload_buflen)

vyper/codegen/expr.py

@@ -130,21 +130,22 @@ def parse_Hex(self):
     # String literals
     def parse_Str(self):
         bytez = self.expr.value.encode("utf-8")
-        return self._make_bytelike(StringT, bytez)
+        return self._make_bytelike(self.context, StringT, bytez)
 
     # Byte literals
     def parse_Bytes(self):
-        return self._make_bytelike(BytesT, self.expr.value)
+        return self._make_bytelike(self.context, BytesT, self.expr.value)
 
     def parse_HexBytes(self):
         # HexBytes already has value as bytes
         assert isinstance(self.expr.value, bytes)
-        return self._make_bytelike(BytesT, self.expr.value)
+        return self._make_bytelike(self.context, BytesT, self.expr.value)
 
-    def _make_bytelike(self, typeclass, bytez):
+    @classmethod
+    def _make_bytelike(cls, context, typeclass, bytez):
         bytez_length = len(bytez)
         btype = typeclass(bytez_length)
-        placeholder = self.context.new_internal_variable(btype)
+        placeholder = context.new_internal_variable(btype)
         seq = []
         seq.append(["mstore", placeholder, bytez_length])
         for i in range(0, len(bytez), 32):