improve error msg for as_wei_value

tests/functional/syntax/test_as_wei_value.py

@@ -1,11 +1,25 @@
 import pytest
 
-from vyper.exceptions import ArgumentException, InvalidType, OverflowException, StructureException
+from vyper.exceptions import (
+    ArgumentException,
+    InvalidLiteral,
+    InvalidType,
+    OverflowException,
+    StructureException,
+)
 
 fail_list = [
     (
         """
 @external
+def foo():
+    x: uint256 = as_wei_value(5, szabo)
+    """,
+        ArgumentException,
+    ),
+    (
+        """
+@external
 def foo():
     x: uint256 = as_wei_value(5, "szaboo")
     """,
@@ -39,6 +53,14 @@ def foo() -> uint256:
     """,
         OverflowException,
     ),
+    (
+        """
+@external
+def foo():
+    x: uint256 = as_wei_value(-1, "szabo")
+    """,
+        InvalidLiteral,
+    ),
 ]
 
 

vyper/builtins/functions.py

@@ -977,12 +977,16 @@ class AsWeiValue(BuiltinFunction):
         ("kether", "grand"): 10**21,
     }
 
-    def get_denomination(self, node):
+    def _get_denomination_node(self, node):
         value = node.args[1]._metadata.get("folded_value")
         if not isinstance(value, vy_ast.Str):
             raise ArgumentException(
                 "Wei denomination must be given as a literal string", node.args[1]
             )
+        return value
+
+    def get_denomination(self, node):
+        value = self._get_denomination_node(node)
         try:
             denom = next(v for k, v in self.wei_denoms.items() if value.value in k)
         except StopIteration:
@@ -1009,6 +1013,9 @@ def fetch_call_return(self, node):
         return self._return_type
 
     def infer_arg_types(self, node, expected_return_typ=None):
+        # raise a better error message by first calling this function
+        # for its side effects of checking the denom
+        self._get_denomination_node(node)
         self._validate_arg_types(node)
         # return a concrete type instead of abstract type
         value_type = get_possible_types_from_node(node.args[0]).pop()