chore: improve error message for subscripted type validation (#3313)

type annotations like `Bytestring` with no length annotation would fail
with an unhelpful error message

tests/parser/syntax/test_bytes.py

@@ -1,7 +1,13 @@
 import pytest
 
 from vyper import compiler
-from vyper.exceptions import InvalidOperation, InvalidType, SyntaxException, TypeMismatch
+from vyper.exceptions import (
+    InvalidOperation,
+    InvalidType,
+    StructureException,
+    SyntaxException,
+    TypeMismatch,
+)
 
 fail_list = [
     (
@@ -77,6 +83,14 @@ def test() -> Bytes[1]:
     """,
         SyntaxException,
     ),
+    (
+        """
+@external
+def foo():
+    a: Bytes = b"abc"
+    """,
+        StructureException,
+    ),
 ]
 
 

tests/parser/syntax/test_dynamic_array.py

@@ -16,6 +16,14 @@
     """,
         StructureException,
     ),
+    (
+        """
+@external
+def foo():
+    a: DynArray = [1, 2, 3]
+    """,
+        StructureException,
+    ),
 ]
 
 

tests/parser/syntax/test_invalids.py

@@ -363,6 +363,13 @@ def a():
     UnknownAttribute,
 )
 
+must_fail(
+    """
+a: HashMap
+""",
+    StructureException,
+)
+
 
 @pytest.mark.parametrize("bad_code,exception_type", fail_list)
 def test_compilation_fails_with_exception(bad_code, exception_type):

tests/parser/syntax/test_string.py

@@ -1,6 +1,7 @@
 import pytest
 
 from vyper import compiler
+from vyper.exceptions import StructureException
 
 valid_list = [
     """
@@ -27,9 +28,31 @@ def foo() -> bool:
     y: String[12] = "test"
     return x != y
     """,
+    """
+@external
+def test() -> String[100]:
+    return "hello world!"
+    """,
 ]
 
 
 @pytest.mark.parametrize("good_code", valid_list)
 def test_string_success(good_code):
     assert compiler.compile_code(good_code) is not None
+
+
+invalid_list = [
+    (
+        """
+@external
+def foo():
+    a: String = "abc"
+    """,
+        StructureException,
+    )
+]
+
+
+@pytest.mark.parametrize("bad_code,exc", invalid_list)
+def test_string_fail(assert_compile_failed, get_contract_with_gas_estimation, bad_code, exc):
+    assert_compile_failed(lambda: get_contract_with_gas_estimation(bad_code), exc)

vyper/semantics/types/utils.py

@@ -104,7 +104,14 @@ def _failwith(type_name):
     if node.id not in namespace:
         _failwith(node.node_source_code)
 
-    return namespace[node.id]
+    typ_ = namespace[node.id]
+    if hasattr(typ_, "from_annotation"):
+        # cases where the object in the namespace is an uninstantiated
+        # type object, ex. Bytestring or DynArray (with no length provided).
+        # call from_annotation to produce a better error message.
+        typ_.from_annotation(node)
+
+    return typ_
 
 
 def get_index_value(node: vy_ast.Index) -> int: