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[ty] Reject functional TypedDict with mismatched name#24295

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sharkdp merged 2 commits intomainfrom
charlie/ty-name
Mar 30, 2026
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[ty] Reject functional TypedDict with mismatched name#24295
sharkdp merged 2 commits intomainfrom
charlie/ty-name

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@charliermarsh charliermarsh commented Mar 30, 2026 •
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Summary

Given BadTypedDict = TypedDict("WrongName", {"name": str}), the conformance test suite suggests we need to raise a diagnostic due to the mismatch between BadTypedDict and WrongName.

See: #24174 (comment).

@astral-sh-bot astral-sh-bot bot added the ty Multi-file analysis & type inference label Mar 30, 2026
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astral-sh-bot bot commented Mar 30, 2026 •
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Typing conformance results improved 🎉

The percentage of diagnostics emitted that were expected errors increased from 86.60% to 86.61%. The percentage of expected errors that received a diagnostic increased from 81.47% to 81.56%. The number of fully passing files improved from 69/132 to 70/132.

Summary

How are test cases classified?

Each test case represents one expected error annotation or a group of annotations sharing a tag. Counts are per test case, not per diagnostic — multiple diagnostics on the same line count as one. Required annotations (E) are true positives when ty flags the expected location and false negatives when it does not. Optional annotations (E?) are true positives when flagged but true negatives (not false negatives) when not. Tagged annotations (E[tag]) require ty to flag exactly one of the tagged lines; tagged multi-annotations (E[tag+]) allow any number up to the tag count. Flagging unexpected locations counts as a false positive.

Metric Old New Diff Outcome
True Positives 866 867 +1 ⏫ (✅)
False Positives 134 134 +0
False Negatives 197 196 -1 ⏬ (✅)
Total Diagnostics 1063 1064 +1 ⏫
Precision 86.60% 86.61% +0.01% ⏫ (✅)
Recall 81.47% 81.56% +0.09% ⏫ (✅)
Passing Files 69/132 70/132 +1 ⏫ (✅)

Test file breakdown

1 file altered
File True Positives False Positives False Negatives Status
typeddicts_alt_syntax.py 7 (+1) ✅ 0 0 (-1) ✅ ✅ Newly Passing 🎉
Total (all files) 867 (+1) ✅ 134 196 (-1) ✅ 70/132

True positives added (1)

1 diagnostic
Test case Diff

typeddicts_alt_syntax.py:31

 
+error[invalid-argument-type] The name of a `TypedDict` (`WrongName`) must match the name of the variable it is assigned to (`BadTypedDict3`)

@charliermarsh charliermarsh marked this pull request as ready for review March 30, 2026 00:36
@astral-sh-bot astral-sh-bot bot requested a review from oconnor663 March 30, 2026 00:36
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astral-sh-bot bot commented Mar 30, 2026 •
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Memory usage report

Memory usage unchanged ✅

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astral-sh-bot bot commented Mar 30, 2026

ecosystem-analyzer results

No diagnostic changes detected ✅

Full report with detailed diff (timing results)

sharkdp
sharkdp approved these changes Mar 30, 2026
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crates/ty_python_semantic/src/types/infer/builder/typed_dict.rs Outdated

let name = if let Some(literal) = name_type.as_string_literal() {
Name::new(literal.value(db))
let name = literal.value(db).to_string();
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Minor

Suggested change
let name = literal.value(db).to_string();
let name = literal.value(db);

@sharkdp sharkdp enabled auto-merge (squash) March 30, 2026 07:17
@sharkdp sharkdp merged commit e765eb0 into main Mar 30, 2026
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@sharkdp sharkdp deleted the charlie/ty-name branch March 30, 2026 07:22
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AlexWaygood commented Mar 30, 2026 •
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On main (following this PR), we now emit an error for this:

from typing import TypedDict

X = TypedDict("Y", {})

but not for this, which seems just as questionable if (per the typing conformance suite) you think it's important for a type checker to enforce that the TypedDict name must exactly match the variable it's assigned to:

from typing import TypedDict

def f(x: str):
    Y = TypedDict(x, {})

(I still feel like this would be better as a bespoke warning-level diagnostic rather than having it use invalid-argument-type. It's just a lint, really; it honestly doesn't need to be enforced for correctness reasons. Though our similar error for NewType definitions is also an error-level diagnostic, so maybe it doesn't matter that much.)

@charliermarsh charliermarsh mentioned this pull request Mar 31, 2026
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carljm added a commit that referenced this pull request Mar 31, 2026
@carljm
Merge branch 'main' into charlie/metaclass
20affc9 
* main: (35 commits)
  Store definition indexes as u32 (#24307)
  Avoid re-using symbol in RUF024 fix (#24316)
  [ty] Add materialization to `Divergent` type (#24255)
  [ty] Make `Divergent` a top-level type variant (#24252)
  [ty] Fix nested global and nonlocal lookups through forwarding scopes (#24279)
  Fetch the cargo-dist binary directly instead of using the installer (#24258)
  [ty] Fix panic on `list[Annotated[()]]` (#24303)
  Don't measure the AST deallocation time in parser benchmarks (#24301)
  Enable CodSpeed's memory benchmarks for simulation benchmarks (#24298)
  Upgrade imara-diff to 0.2.0 (#24299)
  [ty] Represent `InitVar` as a special form internally, not a class (#24248)
  `RUF067`: Allow dunder-named assignments in non-strict mode
  [`pyupgrade`] UP018 should detect more unnecessarily wrapped literals (UP018) (#24093)
  [ty] Remove unused `system.glob` method (#24300)
  [ty] Reject functional TypedDict with mismatched name (#24295)
  Update Rust crate arc-swap to v1.9.0 (#24292)
  [ty] Remove unused `@Todo(Functional TypedDicts)` (#24297)
  Update CodSpeedHQ/action action to v4.12.1 (#24290)
  Update taiki-e/install-action action to v2.69.6 (#24293)
  Update Rust crate toml to v1.0.7 (#24289)
  ...
charliermarsh added a commit that referenced this pull request Mar 31, 2026
@charliermarsh
[ty] Emit diagnostic for functional TypedDict with non-literal name (#…
eb76688 
…24331)

## Summary

See:
#24295 (comment).
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@sharkdp sharkdp sharkdp approved these changes

@carljm carljm Awaiting requested review from carljm carljm is a code owner

@AlexWaygood AlexWaygood Awaiting requested review from AlexWaygood AlexWaygood is a code owner

@dcreager dcreager Awaiting requested review from dcreager dcreager is a code owner

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