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[ty] Minor improvements to assert_type diagnostics #21811

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Merged
AlexWaygood merged 1 commit into from
Dec 5, 2025
Merged

[ty] Minor improvements to assert_type diagnostics #21811

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3 changes: 2 additions & 1 deletion crates/ty_python_semantic/resources/mdtest/directives/assert_type.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,10 +7,11 @@
```py
from typing_extensions import assert_type

def _(x: int):
def _(x: int, y: bool):
assert_type(x, int) # fine
assert_type(x, str) # error: [type-assertion-failure]
assert_type(assert_type(x, int), int)
assert_type(y, int) # error: [type-assertion-failure]
```

## Narrowing
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24 changes: 21 additions & 3 deletions ...resources/mdtest/snapshots/assert_type.md_-_`assert_type`_-_Basic_(c507788da2659ec9).snap
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Expand Up @@ -14,10 +14,11 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/directives/assert_type.m
```
1 | from typing_extensions import assert_type
2 |
3 | def _(x: int):
3 | def _(x: int, y: bool):
4 | assert_type(x, int) # fine
5 | assert_type(x, str) # error: [type-assertion-failure]
6 | assert_type(assert_type(x, int), int)
7 | assert_type(y, int) # error: [type-assertion-failure]
```

# Diagnostics
Expand All @@ -26,15 +27,32 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/directives/assert_type.m
error[type-assertion-failure]: Argument does not have asserted type `str`
--> src/mdtest_snippet.py:5:5
|
3 | def _(x: int):
3 | def _(x: int, y: bool):
4 | assert_type(x, int) # fine
5 | assert_type(x, str) # error: [type-assertion-failure]
| ^^^^^^^^^^^^-^^^^^^
| |
| Inferred type of argument is `int`
| Inferred type is `int`
6 | assert_type(assert_type(x, int), int)
7 | assert_type(y, int) # error: [type-assertion-failure]
|
info: `str` and `int` are not equivalent types
info: rule `type-assertion-failure` is enabled by default

```

```
error[type-assertion-failure]: Argument does not have asserted type `int`
--> src/mdtest_snippet.py:7:5
|
5 | assert_type(x, str) # error: [type-assertion-failure]
6 | assert_type(assert_type(x, int), int)
7 | assert_type(y, int) # error: [type-assertion-failure]
| ^^^^^^^^^^^^-^^^^^^
| |
| Inferred type is `bool`
|
info: `bool` is a subtype of `int`, but they are not equivalent
info: rule `type-assertion-failure` is enabled by default

```
23 changes: 14 additions & 9 deletions crates/ty_python_semantic/src/types/function.rs
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Expand Up @@ -1483,17 +1483,22 @@ impl KnownFunction {

diagnostic.annotate(
Annotation::secondary(context.span(&call_expression.arguments.args[0]))
.message(format_args!(
"Inferred type of argument is `{}`",
actual_ty.display(db),
)),
.message(format_args!("Inferred type is `{}`", actual_ty.display(db),)),
);

diagnostic.info(format_args!(
"`{asserted_type}` and `{inferred_type}` are not equivalent types",
asserted_type = asserted_ty.display(db),
inferred_type = actual_ty.display(db),
));
if actual_ty.is_subtype_of(db, *asserted_ty) {
diagnostic.info(format_args!(
"`{inferred_type}` is a subtype of `{asserted_type}`, but they are not equivalent",
asserted_type = asserted_ty.display(db),
inferred_type = actual_ty.display(db),
));
} else {
diagnostic.info(format_args!(
"`{asserted_type}` and `{inferred_type}` are not equivalent types",
asserted_type = asserted_ty.display(db),
inferred_type = actual_ty.display(db),
));
}

diagnostic.set_concise_message(format_args!(
"Type `{}` does not match asserted type `{}`",
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