[pylint] Implement Pylint typevar-name-mismatch (C0132)

crates/ruff/resources/test/fixtures/pylint/type_param_name_mismatch.py

@@ -0,0 +1,56 @@
+from typing import TypeVar, ParamSpec, NewType, TypeVarTuple
+
+# Errors.
+
+X = TypeVar("T")
+X = TypeVar(name="T")
+
+Y = ParamSpec("T")
+Y = ParamSpec(name="T")
+
+Z = NewType("T", int)
+Z = NewType(name="T", tp=int)
+
+Ws = TypeVarTuple("Ts")
+Ws = TypeVarTuple(name="Ts")
+
+# Non-errors.
+
+T = TypeVar("T")
+T = TypeVar(name="T")
+
+T = ParamSpec("T")
+T = ParamSpec(name="T")
+
+T = NewType("T", int)
+T = NewType(name="T", tp=int)
+
+Ts = TypeVarTuple("Ts")
+Ts = TypeVarTuple(name="Ts")
+
+# Errors, but not covered by this rule.
+
+# Non-string literal name.
+T = TypeVar(some_str)
+T = TypeVar(name=some_str)
+T = TypeVar(1)
+T = TypeVar(name=1)
+T = ParamSpec(some_str)
+T = ParamSpec(name=some_str)
+T = ParamSpec(1)
+T = ParamSpec(name=1)
+T = NewType(some_str, int)
+T = NewType(name=some_str, tp=int)
+T = NewType(1, int)
+T = NewType(name=1, tp=int)
+Ts = TypeVarTuple(some_str)
+Ts = TypeVarTuple(name=some_str)
+Ts = TypeVarTuple(1)
+Ts = TypeVarTuple(name=1)
+
+# No names provided.
+T = TypeVar()
+T = ParamSpec()
+T = NewType()
+T = NewType(tp=int)
+Ts = TypeVarTuple()

crates/ruff/src/checkers/ast/mod.rs

@@ -1655,6 +1655,9 @@ where
                         self.diagnostics.push(diagnostic);
                     }
                 }
+                if self.settings.rules.enabled(Rule::TypeParamNameMismatch) {
+                    pylint::rules::type_param_name_mismatch(self, value, targets);
+                }
                 if self.is_stub {
                     if self.any_enabled(&[
                         Rule::UnprefixedTypeParam,

crates/ruff/src/codes.rs

@@ -156,6 +156,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pyflakes, "901") => (RuleGroup::Unspecified, rules::pyflakes::rules::RaiseNotImplemented),
 
         // pylint
+        (Pylint, "C0132") => (RuleGroup::Unspecified, rules::pylint::rules::TypeParamNameMismatch),
         (Pylint, "C0205") => (RuleGroup::Unspecified, rules::pylint::rules::SingleStringSlots),
         (Pylint, "C0414") => (RuleGroup::Unspecified, rules::pylint::rules::UselessImportAlias),
         (Pylint, "C1901") => (RuleGroup::Nursery, rules::pylint::rules::CompareToEmptyString),

crates/ruff/src/rules/pylint/mod.rs

@@ -85,6 +85,7 @@ mod tests {
         Path::new("too_many_return_statements.py")
     )]
     #[test_case(Rule::TooManyStatements, Path::new("too_many_statements.py"))]
+    #[test_case(Rule::TypeParamNameMismatch, Path::new("type_param_name_mismatch.py"))]
     #[test_case(
         Rule::UnexpectedSpecialMethodSignature,
         Path::new("unexpected_special_method_signature.py")

crates/ruff/src/rules/pylint/rules/mod.rs

@@ -37,6 +37,7 @@ pub(crate) use too_many_arguments::*;
 pub(crate) use too_many_branches::*;
 pub(crate) use too_many_return_statements::*;
 pub(crate) use too_many_statements::*;
+pub(crate) use type_param_name_mismatch::*;
 pub(crate) use unexpected_special_method_signature::*;
 pub(crate) use unnecessary_direct_lambda_call::*;
 pub(crate) use useless_else_on_loop::*;
@@ -84,6 +85,7 @@ mod too_many_arguments;
 mod too_many_branches;
 mod too_many_return_statements;
 mod too_many_statements;
+mod type_param_name_mismatch;
 mod unexpected_special_method_signature;
 mod unnecessary_direct_lambda_call;
 mod useless_else_on_loop;

crates/ruff/src/rules/pylint/rules/type_param_name_mismatch.rs

@@ -0,0 +1,166 @@
+use std::fmt;
+
+use rustpython_parser::ast::{self, Constant, Expr, Ranged};
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for `TypeVar`, `TypeVarTuple`, `ParamSpec`, and `NewType`
+/// definitions in which the name of the type parameter does not match the name
+/// of the variable to which it is assigned.
+///
+/// ## Why is this bad?
+/// When defining a `TypeVar` or a related type parameter, Python allows you to
+/// provide a name for the type parameter. According to [PEP 484], the name
+/// provided to the `TypeVar` constructor must be equal to the name of the
+/// variable to which it is assigned.
+///
+/// ## Example
+/// ```python
+/// from typing import TypeVar
+///
+/// T = TypeVar("U")
+/// ```
+///
+/// Use instead:
+/// ```python
+/// from typing import TypeVar
+///
+/// T = TypeVar("T")
+/// ```
+///
+/// ## References
+/// - [Python documentation: `typing` — Support for type hints](https://docs.python.org/3/library/typing.html)
+/// - [PEP 484 – Type Hints: Generics](https://peps.python.org/pep-0484/#generics)
+///
+/// [PEP 484]:https://peps.python.org/pep-0484/#generics
+#[violation]
+pub struct TypeParamNameMismatch {
+    kind: VarKind,
+    var_name: String,
+    param_name: String,
+}
+
+impl Violation for TypeParamNameMismatch {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let TypeParamNameMismatch {
+            kind,
+            var_name,
+            param_name,
+        } = self;
+        format!("`{kind}` name `{param_name}` does not match assigned variable name `{var_name}`")
+    }
+}
+
+/// PLC0132
+pub(crate) fn type_param_name_mismatch(checker: &mut Checker, value: &Expr, targets: &[Expr]) {
+    let [target] = targets else {
+        return;
+    };
+
+    let Expr::Name(ast::ExprName { id: var_name, .. }) = &target else {
+        return;
+    };
+
+    let Some(param_name) = param_name(value) else {
+        return;
+    };
+
+    if var_name == param_name {
+        return;
+    }
+
+    let Expr::Call(ast::ExprCall { func, .. }) = value else {
+        return;
+    };
+
+    let Some(kind) = checker
+        .semantic()
+        .resolve_call_path(func)
+        .and_then(|call_path| {
+            if checker
+                .semantic()
+                .match_typing_call_path(&call_path, "ParamSpec")
+            {
+                Some(VarKind::ParamSpec)
+            } else if checker
+                .semantic()
+                .match_typing_call_path(&call_path, "TypeVar")
+            {
+                Some(VarKind::TypeVar)
+            } else if checker
+                .semantic()
+                .match_typing_call_path(&call_path, "TypeVarTuple")
+            {
+                Some(VarKind::TypeVarTuple)
+            } else if checker
+                .semantic()
+                .match_typing_call_path(&call_path, "NewType")
+            {
+                Some(VarKind::NewType)
+            } else {
+                None
+            }
+        })
+    else {
+        return;
+    };
+
+    checker.diagnostics.push(Diagnostic::new(
+        TypeParamNameMismatch {
+            kind,
+            var_name: var_name.to_string(),
+            param_name: param_name.to_string(),
+        },
+        value.range(),
+    ));
+}
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum VarKind {
+    TypeVar,
+    ParamSpec,
+    TypeVarTuple,
+    NewType,
+}
+
+impl fmt::Display for VarKind {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            VarKind::TypeVar => fmt.write_str("TypeVar"),
+            VarKind::ParamSpec => fmt.write_str("ParamSpec"),
+            VarKind::TypeVarTuple => fmt.write_str("TypeVarTuple"),
+            VarKind::NewType => fmt.write_str("NewType"),
+        }
+    }
+}
+
+/// Returns the value of the `name` parameter to, e.g., a `TypeVar` constructor.
+fn param_name(value: &Expr) -> Option<&str> {
+    // Handle both `TypeVar("T")` and `TypeVar(name="T")`.
+    let call = value.as_call_expr()?;
+    let name_param = call
+        .keywords
+        .iter()
+        .find(|keyword| {
+            keyword
+                .arg
+                .as_ref()
+                .map_or(false, |keyword| keyword.as_str() == "name")
+        })
+        .map(|keyword| &keyword.value)
+        .or_else(|| call.args.get(0))?;
+    if let Expr::Constant(ast::ExprConstant {
+        value: Constant::Str(name),
+        ..
+    }) = &name_param
+    {
+        Some(name)
+    } else {
+        None
+    }
+}

crates/ruff/src/rules/pylint/snapshots/ruff__rules__pylint__tests__PLC0132_type_param_name_mismatch.py.snap

@@ -0,0 +1,76 @@
+---
+source: crates/ruff/src/rules/pylint/mod.rs
+---
+type_param_name_mismatch.py:5:5: PLC0132 `TypeVar` name `T` does not match assigned variable name `X`
+  |
+3 | # Errors.
+4 | 
+5 | X = TypeVar("T")
+  |     ^^^^^^^^^^^^ PLC0132
+6 | X = TypeVar(name="T")
+  |
+
+type_param_name_mismatch.py:6:5: PLC0132 `TypeVar` name `T` does not match assigned variable name `X`
+  |
+5 | X = TypeVar("T")
+6 | X = TypeVar(name="T")
+  |     ^^^^^^^^^^^^^^^^^ PLC0132
+7 | 
+8 | Y = ParamSpec("T")
+  |
+
+type_param_name_mismatch.py:8:5: PLC0132 `ParamSpec` name `T` does not match assigned variable name `Y`
+  |
+6 | X = TypeVar(name="T")
+7 | 
+8 | Y = ParamSpec("T")
+  |     ^^^^^^^^^^^^^^ PLC0132
+9 | Y = ParamSpec(name="T")
+  |
+
+type_param_name_mismatch.py:9:5: PLC0132 `ParamSpec` name `T` does not match assigned variable name `Y`
+   |
+ 8 | Y = ParamSpec("T")
+ 9 | Y = ParamSpec(name="T")
+   |     ^^^^^^^^^^^^^^^^^^^ PLC0132
+10 | 
+11 | Z = NewType("T", int)
+   |
+
+type_param_name_mismatch.py:11:5: PLC0132 `NewType` name `T` does not match assigned variable name `Z`
+   |
+ 9 | Y = ParamSpec(name="T")
+10 | 
+11 | Z = NewType("T", int)
+   |     ^^^^^^^^^^^^^^^^^ PLC0132
+12 | Z = NewType(name="T", tp=int)
+   |
+
+type_param_name_mismatch.py:12:5: PLC0132 `NewType` name `T` does not match assigned variable name `Z`
+   |
+11 | Z = NewType("T", int)
+12 | Z = NewType(name="T", tp=int)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ PLC0132
+13 | 
+14 | Ws = TypeVarTuple("Ts")
+   |
+
+type_param_name_mismatch.py:14:6: PLC0132 `TypeVarTuple` name `Ts` does not match assigned variable name `Ws`
+   |
+12 | Z = NewType(name="T", tp=int)
+13 | 
+14 | Ws = TypeVarTuple("Ts")
+   |      ^^^^^^^^^^^^^^^^^^ PLC0132
+15 | Ws = TypeVarTuple(name="Ts")
+   |
+
+type_param_name_mismatch.py:15:6: PLC0132 `TypeVarTuple` name `Ts` does not match assigned variable name `Ws`
+   |
+14 | Ws = TypeVarTuple("Ts")
+15 | Ws = TypeVarTuple(name="Ts")
+   |      ^^^^^^^^^^^^^^^^^^^^^^^ PLC0132
+16 | 
+17 | # Non-errors.
+   |
+
+