66 lines
2.0 KiB
Rust
66 lines
2.0 KiB
Rust
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use clippy_utils::diagnostics::span_lint;
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use rustc_ast::ast::{Expr, ExprKind, Stmt, StmtKind};
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use rustc_lint::{EarlyContext, EarlyLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for nested assignments.
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///
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/// ### Why is this bad?
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/// While this is in most cases already a type mismatch,
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/// the result of an assignment being `()` can throw off people coming from languages like python or C,
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/// where such assignments return a copy of the assigned value.
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///
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/// ### Example
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/// ```rust
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///# let (a, b);
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/// a = b = 42;
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/// ```
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/// Use instead:
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/// ```rust
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///# let (a, b);
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/// b = 42;
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/// a = b;
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/// ```
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#[clippy::version = "1.65.0"]
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pub MULTI_ASSIGNMENTS,
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suspicious,
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"instead of using `a = b = c;` use `a = c; b = c;`"
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}
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declare_lint_pass!(MultiAssignments => [MULTI_ASSIGNMENTS]);
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fn strip_paren_blocks(expr: &Expr) -> &Expr {
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match &expr.kind {
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ExprKind::Paren(e) => strip_paren_blocks(e),
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ExprKind::Block(b, _) => {
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if let [
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Stmt {
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kind: StmtKind::Expr(e),
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..
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},
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] = &b.stmts[..]
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{
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strip_paren_blocks(e)
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} else {
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expr
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}
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},
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_ => expr,
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}
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}
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impl EarlyLintPass for MultiAssignments {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if let ExprKind::Assign(target, source, _) = &expr.kind {
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if let ExprKind::Assign(_target, _source, _) = &strip_paren_blocks(target).kind {
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span_lint(cx, MULTI_ASSIGNMENTS, expr.span, "assignments don't nest intuitively");
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};
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if let ExprKind::Assign(_target, _source, _) = &strip_paren_blocks(source).kind {
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span_lint(cx, MULTI_ASSIGNMENTS, expr.span, "assignments don't nest intuitively");
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}
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};
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}
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}
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