fix[ux]: typechecking for loop annotation of list variable by tserg · Pull Request #4550 · vyperlang/vyper

tserg · 2025-03-31T02:34:47Z

What I did

How I did it

Add a check that the type derived for a variable list matches the iterator type specified in the for loop annotation.

How to verify it

See new tests.

Commit message

This commit fixes a compiler panic for `for` loops by properly catching
type mismatch between the iterator and target during semantic analysis

Description for the changelog

Typechecking for loop annotation of variable list

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codecov · 2025-03-31T02:53:44Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.57%. Comparing base (cef84e8) to head (579362a).
Report is 94 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4550      +/-   ##
==========================================
+ Coverage   92.35%   92.57%   +0.22%     
==========================================
  Files         123      123              
  Lines       17543    17471      -72     
  Branches     2961     2951      -10     
==========================================
- Hits        16201    16173      -28     
+ Misses        938      894      -44     
  Partials      404      404

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charles-cooper · 2025-03-31T14:02:45Z

vyper/semantics/analysis/local.py

+                if not isinstance(iter_type, (DArrayT, SArrayT)):
+                    raise InvalidType("Not an iterable type", iter_node)
+
+                if not target_type.compare_type(iter_type.value_type):


what happens if we don't move this into the try/except block?

it would still work, just that it is a redundant check in the case of a literal list - but I think this is acceptable because your suggestion makes the code more readable.

charles-cooper

looks reasonable. @cyberthirst please take a look

cyberthirst · 2025-04-02T10:07:23Z

possibly another for related bug:

def foo():
    a: DynArray[DynArray[uint256, 10], 10] = []
    for i: DynArray[uint256, 10] in a:
        for j: i in i:
            pass

vyper.exceptions.CompilerPanic: Not a type: VarInfo(typ=DynArray[uint256, 10], location=<DataLocation.UNSET: 'unset'>, modifiability=<Modifiability.RUNTIME_CONSTANT: 'runtime_constant'>, is_public=False, decl_node=vyper.ast.nodes.AnnAssign:
---> 1 def foo():
-------^
     2     a: DynArray[DynArray[uint256, 10], 10] = [])

  contract "tests/custom/test.vy:4", function "foo", line 4:15 
       3     for i: DynArray[uint256, 10] in a:
  ---> 4         for j: i in i:
  ----------------------^
       5             pass


This is an unhandled internal compiler error. Please create an issue on Github to notify the developers!
https://github.com/vyperlang/vyper/issues/new?template=bug.md

cyberthirst · 2025-04-02T10:11:39Z

maybe we could improve the suggestion here?

def foo():
    for i: DynArray[uint256, 10] in [[[]]][0]:
        for j: uint256 in i:
            pass

vyper.exceptions.TypeMismatch: Expected DynArray[uint256, 10][1] but literal can only be cast as DynArray[DynArray[GenericTypeAcceptor(<class 'vyper.semantics.types.bytestrings.BytesT'>), 1], 1] or DynArray[DynArray[uint96, 1], 1].

  contract "tests/custom/test.vy:2", function "foo", line 2:36 
       1 def foo():
  ---> 2     for i: DynArray[uint256, 10] in [[[]]][0]:
  -------------------------------------------^
       3         for j: uint256 in i:

cyberthirst · 2025-04-02T10:14:05Z

this fails on an assertion error:

def foo():
    a: DynArray[DynArray[uint256, 10], 10] = []
    for i: DynArray[uint256, 10] in [k for k in a]:
        for j: uint256 in i:
            pass

AssertionError

charles-cooper · 2025-04-02T14:40:40Z

@cyberthirst these seem out of scope, right? like they were pre-existing errors prior to this PR?

cyberthirst · 2025-04-03T08:29:20Z

@cyberthirst these seem out of scope, right? like they were pre-existing errors prior to this PR?

yeah, I think we should lift those to a separate issue/PR

cyberthirst · 2025-04-04T13:04:42Z

vyper/semantics/analysis/local.py


+        if not target_type.compare_type(iter_type.value_type):
+            raise TypeMismatch(
+                f"Iterator has a type of {target_type} but iterable has a type of {iter_type}",


maybe it would be better to refer to the value type inside the iterable?

also, I think it would be better to point to the iterator instead of the iterable

because most likely the iterable is the correct thing, but the iterator is incorrectly annotated

so like - "TypeMismatch(Expected type of {iter_type.value_type}..." and then instead of using iter_node use the iterator node?

Done! I had to pass target_node to _analyse_list_iter in order to raise the iterator node in the exception, which makes the function signature for _analyse_list_iter different from _analyse_range_iter (shouldn't be an issue?).

cyberthirst · 2025-04-04T13:06:41Z

this should also close #3988 which should be the original issue where this bug was described

cyberthirst · 2025-04-04T13:10:12Z

this fails on an assertion error:

def foo():
    a: DynArray[DynArray[uint256, 10], 10] = []
    for i: DynArray[uint256, 10] in [k for k in a]:
        for j: uint256 in i:
            pass

AssertionError

opened a new issue: #4557

cyberthirst · 2025-04-04T13:29:38Z

maybe we could improve the suggestion here?

def foo():
    for i: DynArray[uint256, 10] in [[[]]][0]:
        for j: uint256 in i:
            pass

vyper.exceptions.TypeMismatch: Expected DynArray[uint256, 10][1] but literal can only be cast as DynArray[DynArray[GenericTypeAcceptor(<class 'vyper.semantics.types.bytestrings.BytesT'>), 1], 1] or DynArray[DynArray[uint96, 1], 1].

 contract "tests/custom/test.vy:2", function "foo", line 2:36 
      1 def foo():
 ---> 2     for i: DynArray[uint256, 10] in [[[]]][0]:
 -------------------------------------------^
      3         for j: uint256 in i:

opened a new issue: #4558

cyberthirst · 2025-04-04T13:37:33Z

vyper.exceptions.CompilerPanic: Not a type:

opened a new issue: #4559

tserg added 2 commits March 31, 2025 10:29

check iterable and iterator type for lists

435ff26

add tests

2b1763f

tserg requested a review from charles-cooper March 31, 2025 13:59

charles-cooper reviewed Mar 31, 2025

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apply cc suggestion

f91b127

charles-cooper approved these changes Apr 1, 2025

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charles-cooper requested a review from cyberthirst April 1, 2025 10:54

cyberthirst reviewed Apr 4, 2025

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tserg and others added 2 commits April 5, 2025 16:10

apply cyberthirst suggestion

46a4ba1

reverse arg order

579362a

charles-cooper approved these changes Apr 6, 2025

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charles-cooper changed the title ~~fix[ux]: typechecking for loop annotation of variable list~~ fix[ux]: typechecking for loop annotation of list variable Apr 6, 2025

cyberthirst approved these changes Apr 7, 2025

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charles-cooper merged commit ded0394 into vyperlang:master Apr 7, 2025
163 checks passed

tserg deleted the fix/for_typecheck branch April 8, 2025 04:32

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tserg commented Mar 31, 2025 •

edited by charles-cooper

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