Implement runtime-import-in-type-checking-block (TYP004) (#2146)

README.md

@@ -1202,6 +1202,7 @@ For more, see [flake8-type-checking](https://pypi.org/project/flake8-type-checki
 
 | Code | Name | Message | Fix |
 | ---- | ---- | ------- | --- |
+| TYP004 | runtime-import-in-type-checking-block | Move import `{}` out of type-checking block. Import is used for more than type hinting. |  |
 | TYP005 | empty-type-checking-block | Found empty type-checking block |  |
 
 ### tryceratops (TRY)

resources/test/fixtures/flake8_type_checking/TYP004_1.py

@@ -0,0 +1,5 @@
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from datetime import datetime
+x = datetime

resources/test/fixtures/flake8_type_checking/TYP004_2.py

@@ -0,0 +1,8 @@
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from datetime import date
+
+
+def example():
+    return date()

resources/test/fixtures/flake8_type_checking/TYP004_3.py

@@ -0,0 +1,6 @@
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import Any
+
+    CustomType = Any

resources/test/fixtures/flake8_type_checking/TYP004_4.py

@@ -0,0 +1,11 @@
+from typing import TYPE_CHECKING, Type
+
+if TYPE_CHECKING:
+    from typing import Any
+
+
+def example(*args: Any, **kwargs: Any):
+    return
+
+
+my_type: Type[Any] | Any

resources/test/fixtures/flake8_type_checking/TYP004_5.py

@@ -0,0 +1,8 @@
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import List, Sequence, Set
+
+
+def example(a: List[int], /, b: Sequence[int], *, c: Set[int]):
+    return

resources/test/fixtures/flake8_type_checking/TYP004_6.py

@@ -0,0 +1,10 @@
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from pandas import DataFrame
+
+
+def example():
+    from pandas import DataFrame
+
+    x = DataFrame

resources/test/fixtures/flake8_type_checking/TYP004_7.py

@@ -0,0 +1,10 @@
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import AsyncIterator, List
+
+
+class Example:
+    async def example(self) -> AsyncIterator[List[str]]:
+        yield 0

resources/test/fixtures/flake8_type_checking/TYP004_8.py

@@ -0,0 +1,7 @@
+from typing import TYPE_CHECKING
+from weakref import WeakKeyDictionary
+
+if TYPE_CHECKING:
+    from typing import Any
+
+d = WeakKeyDictionary["Any", "Any"]()

ruff.schema.json

@@ -1784,6 +1784,7 @@
         "TYP",
         "TYP0",
         "TYP00",
+        "TYP004",
         "TYP005",
         "UP",
         "UP0",

src/ast/types.rs

@@ -33,6 +33,10 @@ impl Range {
     pub fn from_located<T>(located: &Located<T>) -> Self {
         Range::new(located.location, located.end_location.unwrap())
     }
+
+    pub fn contains(&self, other: &Range) -> bool {
+        self.location <= other.location && self.end_location >= other.end_location
+    }
 }
 
 #[derive(Debug)]
@@ -130,8 +134,22 @@ pub struct Binding<'a> {
     /// The statement in which the [`Binding`] was defined.
     pub source: Option<RefEquality<'a, Stmt>>,
     /// Tuple of (scope index, range) indicating the scope and range at which
-    /// the binding was last used.
-    pub used: Option<(usize, Range)>,
+    /// the binding was last used in a runtime context.
+    pub runtime_usage: Option<(usize, Range)>,
+    /// Tuple of (scope index, range) indicating the scope and range at which
+    /// the binding was last used in a typing-time context.
+    pub typing_usage: Option<(usize, Range)>,
+    /// Tuple of (scope index, range) indicating the scope and range at which
+    /// the binding was last used in a synthetic context. This is used for
+    /// (e.g.) `__future__` imports, explicit re-exports, and other bindings
+    /// that should be considered used even if they're never referenced.
+    pub synthetic_usage: Option<(usize, Range)>,
+}
+
+#[derive(Copy, Clone)]
+pub enum UsageContext {
+    Runtime,
+    Typing,
 }
 
 // Pyflakes defines the following binding hierarchy (via inheritance):
@@ -152,6 +170,19 @@ pub struct Binding<'a> {
 //        FutureImportation
 
 impl<'a> Binding<'a> {
+    pub fn mark_used(&mut self, scope: usize, range: Range, context: UsageContext) {
+        match context {
+            UsageContext::Runtime => self.runtime_usage = Some((scope, range)),
+            UsageContext::Typing => self.typing_usage = Some((scope, range)),
+        }
+    }
+
+    pub fn used(&self) -> bool {
+        self.runtime_usage.is_some()
+            || self.synthetic_usage.is_some()
+            || self.typing_usage.is_some()
+    }
+
     pub fn is_definition(&self) -> bool {
         matches!(
             self.kind,