mirror of https://github.com/astral-sh/ruff
415 lines
14 KiB
Rust
415 lines
14 KiB
Rust
//! [`SemanticSyntaxChecker`] for AST-based syntax errors.
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//!
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//! This checker is not responsible for traversing the AST itself. Instead, its
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//! [`SemanticSyntaxChecker::visit_stmt`] and [`SemanticSyntaxChecker::visit_expr`] methods should
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//! be called in a parent `Visitor`'s `visit_stmt` and `visit_expr` methods, respectively.
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use std::fmt::Display;
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use ruff_python_ast::{
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self as ast,
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visitor::{walk_expr, Visitor},
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Expr, IrrefutablePatternKind, PythonVersion, Stmt, StmtExpr, StmtImportFrom,
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};
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use ruff_text_size::{Ranged, TextRange};
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#[derive(Debug)]
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pub struct SemanticSyntaxChecker {
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/// The checker has traversed past the `__future__` import boundary.
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///
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/// For example, the checker could be visiting `x` in:
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///
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/// ```python
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/// from __future__ import annotations
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///
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/// import os
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///
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/// x: int = 1
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/// ```
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///
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/// Python considers it a syntax error to import from `__future__` after any other
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/// non-`__future__`-importing statements.
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seen_futures_boundary: bool,
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}
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impl SemanticSyntaxChecker {
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pub fn new() -> Self {
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Self {
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seen_futures_boundary: false,
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}
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}
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}
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impl SemanticSyntaxChecker {
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fn add_error<Ctx: SemanticSyntaxContext>(
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context: &Ctx,
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kind: SemanticSyntaxErrorKind,
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range: TextRange,
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) {
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context.report_semantic_error(SemanticSyntaxError {
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kind,
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range,
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python_version: context.python_version(),
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});
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}
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fn check_stmt<Ctx: SemanticSyntaxContext>(&mut self, stmt: &ast::Stmt, ctx: &Ctx) {
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match stmt {
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Stmt::ImportFrom(StmtImportFrom { range, module, .. }) => {
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if self.seen_futures_boundary && matches!(module.as_deref(), Some("__future__")) {
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Self::add_error(ctx, SemanticSyntaxErrorKind::LateFutureImport, *range);
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}
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}
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Stmt::Match(match_stmt) => {
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Self::irrefutable_match_case(match_stmt, ctx);
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}
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Stmt::FunctionDef(ast::StmtFunctionDef { type_params, .. })
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| Stmt::ClassDef(ast::StmtClassDef { type_params, .. })
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| Stmt::TypeAlias(ast::StmtTypeAlias { type_params, .. }) => {
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if let Some(type_params) = type_params {
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Self::duplicate_type_parameter_name(type_params, ctx);
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}
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}
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_ => {}
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}
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}
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fn duplicate_type_parameter_name<Ctx: SemanticSyntaxContext>(
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type_params: &ast::TypeParams,
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ctx: &Ctx,
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) {
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if type_params.len() < 2 {
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return;
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}
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for (i, type_param) in type_params.iter().enumerate() {
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if type_params
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.iter()
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.take(i)
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.any(|t| t.name().id == type_param.name().id)
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{
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// test_ok non_duplicate_type_parameter_names
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// type Alias[T] = list[T]
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// def f[T](t: T): ...
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// class C[T]: ...
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// class C[T, U, V]: ...
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// type Alias[T, U: str, V: (str, bytes), *Ts, **P, D = default] = ...
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// test_err duplicate_type_parameter_names
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// type Alias[T, T] = ...
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// def f[T, T](t: T): ...
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// class C[T, T]: ...
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// type Alias[T, U: str, V: (str, bytes), *Ts, **P, T = default] = ...
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// def f[T, T, T](): ... # two errors
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// def f[T, *T](): ... # star is still duplicate
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// def f[T, **T](): ... # as is double star
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Self::add_error(
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ctx,
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SemanticSyntaxErrorKind::DuplicateTypeParameter,
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type_param.range(),
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);
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}
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}
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}
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fn irrefutable_match_case<Ctx: SemanticSyntaxContext>(stmt: &ast::StmtMatch, ctx: &Ctx) {
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// test_ok irrefutable_case_pattern_at_end
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// match x:
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// case 2: ...
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// case var: ...
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// match x:
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// case 2: ...
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// case _: ...
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// match x:
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// case var if True: ... # don't try to refute a guarded pattern
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// case 2: ...
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// test_err irrefutable_case_pattern
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// match x:
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// case var: ... # capture pattern
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// case 2: ...
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// match x:
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// case _: ...
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// case 2: ... # wildcard pattern
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// match x:
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// case var1 as var2: ... # as pattern with irrefutable left-hand side
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// case 2: ...
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// match x:
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// case enum.variant | var: ... # or pattern with irrefutable part
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// case 2: ...
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for case in stmt
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.cases
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.iter()
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.rev()
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.skip(1)
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.filter_map(|case| match case.guard {
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Some(_) => None,
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None => case.pattern.irrefutable_pattern(),
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})
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{
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Self::add_error(
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ctx,
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SemanticSyntaxErrorKind::IrrefutableCasePattern(case.kind),
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case.range,
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);
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}
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}
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pub fn visit_stmt<Ctx: SemanticSyntaxContext>(&mut self, stmt: &ast::Stmt, ctx: &Ctx) {
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// update internal state
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match stmt {
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Stmt::Expr(StmtExpr { value, .. })
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if !ctx.seen_docstring_boundary() && value.is_string_literal_expr() => {}
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Stmt::ImportFrom(StmtImportFrom { module, .. }) => {
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// Allow __future__ imports until we see a non-__future__ import.
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if !matches!(module.as_deref(), Some("__future__")) {
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self.seen_futures_boundary = true;
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}
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}
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_ => {
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self.seen_futures_boundary = true;
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}
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}
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// check for errors
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self.check_stmt(stmt, ctx);
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}
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pub fn visit_expr<Ctx: SemanticSyntaxContext>(&mut self, expr: &Expr, ctx: &Ctx) {
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match expr {
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Expr::ListComp(ast::ExprListComp {
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elt, generators, ..
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})
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| Expr::SetComp(ast::ExprSetComp {
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elt, generators, ..
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})
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| Expr::Generator(ast::ExprGenerator {
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elt, generators, ..
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}) => Self::check_generator_expr(elt, generators, ctx),
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Expr::DictComp(ast::ExprDictComp {
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key,
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value,
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generators,
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..
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}) => {
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Self::check_generator_expr(key, generators, ctx);
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Self::check_generator_expr(value, generators, ctx);
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}
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_ => {}
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}
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}
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/// Add a [`SyntaxErrorKind::ReboundComprehensionVariable`] if `expr` rebinds an iteration
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/// variable in `generators`.
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fn check_generator_expr<Ctx: SemanticSyntaxContext>(
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expr: &Expr,
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comprehensions: &[ast::Comprehension],
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ctx: &Ctx,
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) {
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let rebound_variables = {
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let mut visitor = ReboundComprehensionVisitor {
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comprehensions,
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rebound_variables: Vec::new(),
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};
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visitor.visit_expr(expr);
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visitor.rebound_variables
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};
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// TODO(brent) with multiple diagnostic ranges, we could mark both the named expr (current)
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// and the name expr being rebound
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for range in rebound_variables {
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// test_err rebound_comprehension_variable
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// [(a := 0) for a in range(0)]
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// {(a := 0) for a in range(0)}
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// {(a := 0): val for a in range(0)}
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// {key: (a := 0) for a in range(0)}
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// ((a := 0) for a in range(0))
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// [[(a := 0)] for a in range(0)]
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// [(a := 0) for b in range (0) for a in range(0)]
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// [(a := 0) for a in range (0) for b in range(0)]
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// [((a := 0), (b := 1)) for a in range (0) for b in range(0)]
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// test_ok non_rebound_comprehension_variable
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// [a := 0 for x in range(0)]
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Self::add_error(
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ctx,
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SemanticSyntaxErrorKind::ReboundComprehensionVariable,
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range,
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);
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}
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}
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}
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impl Default for SemanticSyntaxChecker {
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fn default() -> Self {
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Self::new()
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}
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}
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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pub struct SemanticSyntaxError {
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pub kind: SemanticSyntaxErrorKind,
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pub range: TextRange,
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pub python_version: PythonVersion,
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}
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impl Display for SemanticSyntaxError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match &self.kind {
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SemanticSyntaxErrorKind::LateFutureImport => {
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f.write_str("__future__ imports must be at the top of the file")
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}
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SemanticSyntaxErrorKind::ReboundComprehensionVariable => {
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f.write_str("assignment expression cannot rebind comprehension variable")
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}
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SemanticSyntaxErrorKind::DuplicateTypeParameter => {
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f.write_str("duplicate type parameter")
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}
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SemanticSyntaxErrorKind::IrrefutableCasePattern(kind) => match kind {
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// These error messages are taken from CPython's syntax errors
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IrrefutablePatternKind::Name(name) => {
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write!(
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f,
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"name capture `{name}` makes remaining patterns unreachable"
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)
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}
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IrrefutablePatternKind::Wildcard => {
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f.write_str("wildcard makes remaining patterns unreachable")
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}
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},
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}
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}
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}
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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pub enum SemanticSyntaxErrorKind {
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/// Represents the use of a `__future__` import after the beginning of a file.
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///
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/// ## Examples
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///
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/// ```python
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/// from pathlib import Path
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///
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/// from __future__ import annotations
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/// ```
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///
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/// This corresponds to the [`late-future-import`] (`F404`) rule in ruff.
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///
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/// [`late-future-import`]: https://docs.astral.sh/ruff/rules/late-future-import/
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LateFutureImport,
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/// Represents the rebinding of the iteration variable of a list, set, or dict comprehension or
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/// a generator expression.
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///
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/// ## Examples
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///
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/// ```python
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/// [(a := 0) for a in range(0)]
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/// {(a := 0) for a in range(0)}
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/// {(a := 0): val for a in range(0)}
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/// {key: (a := 0) for a in range(0)}
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/// ((a := 0) for a in range(0))
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/// ```
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ReboundComprehensionVariable,
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/// Represents a duplicate type parameter name in a function definition, class definition, or
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/// type alias statement.
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///
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/// ## Examples
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///
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/// ```python
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/// type Alias[T, T] = ...
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/// def f[T, T](t: T): ...
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/// class C[T, T]: ...
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/// ```
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DuplicateTypeParameter,
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/// Represents an irrefutable `case` pattern before the last `case` in a `match` statement.
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///
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/// According to the [Python reference], "a match statement may have at most one irrefutable
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/// case block, and it must be last."
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///
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/// ## Examples
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///
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/// ```python
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/// match x:
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/// case value: ... # irrefutable capture pattern
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/// case other: ...
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///
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/// match x:
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/// case _: ... # irrefutable wildcard pattern
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/// case other: ...
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/// ```
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///
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/// [Python reference]: https://docs.python.org/3/reference/compound_stmts.html#irrefutable-case-blocks
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IrrefutableCasePattern(IrrefutablePatternKind),
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}
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/// Searches for the first named expression (`x := y`) rebinding one of the `iteration_variables` in
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/// a comprehension or generator expression.
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struct ReboundComprehensionVisitor<'a> {
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comprehensions: &'a [ast::Comprehension],
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rebound_variables: Vec<TextRange>,
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}
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impl Visitor<'_> for ReboundComprehensionVisitor<'_> {
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fn visit_expr(&mut self, expr: &Expr) {
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if let Expr::Named(ast::ExprNamed { target, .. }) = expr {
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if let Expr::Name(ast::ExprName { id, range, .. }) = &**target {
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if self.comprehensions.iter().any(|comp| {
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comp.target
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.as_name_expr()
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.is_some_and(|name| name.id == *id)
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}) {
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self.rebound_variables.push(*range);
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}
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};
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}
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walk_expr(self, expr);
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}
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}
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pub trait SemanticSyntaxContext {
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/// Returns `true` if a module's docstring boundary has been passed.
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fn seen_docstring_boundary(&self) -> bool;
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/// The target Python version for detecting backwards-incompatible syntax changes.
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fn python_version(&self) -> PythonVersion;
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fn report_semantic_error(&self, error: SemanticSyntaxError);
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}
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#[derive(Default)]
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pub struct SemanticSyntaxCheckerVisitor<Ctx> {
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checker: SemanticSyntaxChecker,
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context: Ctx,
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}
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impl<Ctx> SemanticSyntaxCheckerVisitor<Ctx> {
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pub fn new(context: Ctx) -> Self {
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Self {
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checker: SemanticSyntaxChecker::new(),
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context,
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}
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}
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pub fn into_context(self) -> Ctx {
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self.context
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}
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}
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impl<Ctx> Visitor<'_> for SemanticSyntaxCheckerVisitor<Ctx>
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where
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Ctx: SemanticSyntaxContext,
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{
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fn visit_stmt(&mut self, stmt: &'_ Stmt) {
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self.checker.visit_stmt(stmt, &self.context);
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ruff_python_ast::visitor::walk_stmt(self, stmt);
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}
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fn visit_expr(&mut self, expr: &'_ Expr) {
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self.checker.visit_expr(expr, &self.context);
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ruff_python_ast::visitor::walk_expr(self, expr);
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}
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}
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