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[ty] Correctly handle calls to functions marked as returning Never / NoReturn (#18333)
## Summary `ty` does not understand that calls to functions which have been annotated as having a return type of `Never` / `NoReturn` are terminal. This PR fixes that, by adding new reachability constraints when call expressions are seen. If the call expression evaluates to `Never`, the code following it will be considered to be unreachable. Note that, for adding these constraints, we only consider call expressions at the statement level, and that too only inside function scopes. This is because otherwise, the number of such constraints becomes too high, and evaluating them later on during type inference results in a major performance degradation. Fixes https://github.com/astral-sh/ty/issues/180 ## Test Plan New mdtests. ## Ecosystem changes This PR removes the following false-positives: - "Function can implicitly return `None`, which is not assignable to ...". - "Name `foo` used when possibly not defind" - because the branch in which it is not defined has a `NoReturn` call, or when `foo` was imported in a `try`, and the except had a `NoReturn` call. --------- Co-authored-by: David Peter <mail@david-peter.de>
This commit is contained in:
Abhijeet Prasad Bodas
GitHub
parent
a33cff2b12
commit
f4bd74ab6a
10 changed files with 437 additions and 72 deletions
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@ -3,7 +3,7 @@ source: crates/ty_test/src/lib.rs
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expression: snapshot
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---
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---
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mdtest name: assert_never.md - `assert_never` - Basic functionality
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mdtest name: assert_never.md - `assert_never` - Basic functionality - Diagnostics
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mdtest path: crates/ty_python_semantic/resources/mdtest/directives/assert_never.md
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---
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@ -15,35 +15,47 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/directives/assert_never.
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1 | from typing_extensions import assert_never, Never, Any
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2 | from ty_extensions import Unknown
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3 |
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4 | def _(never: Never, any_: Any, unknown: Unknown, flag: bool):
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5 | assert_never(never) # fine
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4 | def _():
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5 | assert_never(0) # error: [type-assertion-failure]
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6 |
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7 | assert_never(0) # error: [type-assertion-failure]
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7 | def _():
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8 | assert_never("") # error: [type-assertion-failure]
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9 | assert_never(None) # error: [type-assertion-failure]
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10 | assert_never([]) # error: [type-assertion-failure]
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11 | assert_never({}) # error: [type-assertion-failure]
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12 | assert_never(()) # error: [type-assertion-failure]
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13 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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14 |
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15 | assert_never(any_) # error: [type-assertion-failure]
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16 | assert_never(unknown) # error: [type-assertion-failure]
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9 |
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10 | def _():
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11 | assert_never(None) # error: [type-assertion-failure]
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12 |
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13 | def _():
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14 | assert_never([]) # error: [type-assertion-failure]
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15 |
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16 | def _():
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17 | assert_never({}) # error: [type-assertion-failure]
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18 |
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19 | def _():
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20 | assert_never(()) # error: [type-assertion-failure]
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21 |
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22 | def _(flag: bool, never: Never):
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23 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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24 |
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25 | def _(any_: Any):
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26 | assert_never(any_) # error: [type-assertion-failure]
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27 |
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28 | def _(unknown: Unknown):
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29 | assert_never(unknown) # error: [type-assertion-failure]
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```
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# Diagnostics
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:7:5
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--> src/mdtest_snippet.py:5:5
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5 | assert_never(never) # fine
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6 |
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7 | assert_never(0) # error: [type-assertion-failure]
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4 | def _():
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5 | assert_never(0) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^-^
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| Inferred type of argument is `Literal[0]`
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8 | assert_never("") # error: [type-assertion-failure]
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9 | assert_never(None) # error: [type-assertion-failure]
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6 |
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7 | def _():
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info: `Never` and `Literal[0]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -54,13 +66,13 @@ info: rule `type-assertion-failure` is enabled by default
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:8:5
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7 | assert_never(0) # error: [type-assertion-failure]
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7 | def _():
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8 | assert_never("") # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^--^
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| Inferred type of argument is `Literal[""]`
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9 | assert_never(None) # error: [type-assertion-failure]
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10 | assert_never([]) # error: [type-assertion-failure]
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9 |
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10 | def _():
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info: `Never` and `Literal[""]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -69,16 +81,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:9:5
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--> src/mdtest_snippet.py:11:5
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7 | assert_never(0) # error: [type-assertion-failure]
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8 | assert_never("") # error: [type-assertion-failure]
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9 | assert_never(None) # error: [type-assertion-failure]
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10 | def _():
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11 | assert_never(None) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^----^
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| Inferred type of argument is `None`
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10 | assert_never([]) # error: [type-assertion-failure]
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11 | assert_never({}) # error: [type-assertion-failure]
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12 |
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13 | def _():
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info: `Never` and `None` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -87,16 +98,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:10:5
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--> src/mdtest_snippet.py:14:5
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8 | assert_never("") # error: [type-assertion-failure]
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9 | assert_never(None) # error: [type-assertion-failure]
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10 | assert_never([]) # error: [type-assertion-failure]
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13 | def _():
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14 | assert_never([]) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^--^
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| Inferred type of argument is `list[Unknown]`
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11 | assert_never({}) # error: [type-assertion-failure]
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12 | assert_never(()) # error: [type-assertion-failure]
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15 |
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16 | def _():
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info: `Never` and `list[Unknown]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -105,16 +115,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:11:5
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--> src/mdtest_snippet.py:17:5
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9 | assert_never(None) # error: [type-assertion-failure]
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10 | assert_never([]) # error: [type-assertion-failure]
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11 | assert_never({}) # error: [type-assertion-failure]
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16 | def _():
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17 | assert_never({}) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^--^
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| Inferred type of argument is `dict[Unknown, Unknown]`
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12 | assert_never(()) # error: [type-assertion-failure]
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13 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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18 |
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19 | def _():
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info: `Never` and `dict[Unknown, Unknown]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -123,15 +132,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:12:5
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--> src/mdtest_snippet.py:20:5
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10 | assert_never([]) # error: [type-assertion-failure]
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11 | assert_never({}) # error: [type-assertion-failure]
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12 | assert_never(()) # error: [type-assertion-failure]
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19 | def _():
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20 | assert_never(()) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^--^
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| Inferred type of argument is `tuple[()]`
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13 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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21 |
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22 | def _(flag: bool, never: Never):
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info: `Never` and `tuple[()]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -140,16 +149,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:13:5
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--> src/mdtest_snippet.py:23:5
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11 | assert_never({}) # error: [type-assertion-failure]
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12 | assert_never(()) # error: [type-assertion-failure]
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13 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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22 | def _(flag: bool, never: Never):
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23 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^--------------------^
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| Inferred type of argument is `Literal[1]`
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14 |
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15 | assert_never(any_) # error: [type-assertion-failure]
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24 |
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25 | def _(any_: Any):
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info: `Never` and `Literal[1]` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -158,15 +166,15 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:15:5
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--> src/mdtest_snippet.py:26:5
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13 | assert_never(1 if flag else never) # error: [type-assertion-failure]
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14 |
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15 | assert_never(any_) # error: [type-assertion-failure]
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25 | def _(any_: Any):
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26 | assert_never(any_) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^----^
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| Inferred type of argument is `Any`
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16 | assert_never(unknown) # error: [type-assertion-failure]
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27 |
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28 | def _(unknown: Unknown):
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info: `Never` and `Any` are not equivalent types
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info: rule `type-assertion-failure` is enabled by default
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@ -175,10 +183,10 @@ info: rule `type-assertion-failure` is enabled by default
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```
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error[type-assertion-failure]: Argument does not have asserted type `Never`
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--> src/mdtest_snippet.py:16:5
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--> src/mdtest_snippet.py:29:5
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15 | assert_never(any_) # error: [type-assertion-failure]
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16 | assert_never(unknown) # error: [type-assertion-failure]
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28 | def _(unknown: Unknown):
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29 | assert_never(unknown) # error: [type-assertion-failure]
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| ^^^^^^^^^^^^^-------^
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| |
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| Inferred type of argument is `Unknown`
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