diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/bool_to_int_with_if.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/bool_to_int_with_if.rs | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/bool_to_int_with_if.rs b/src/tools/clippy/clippy_lints/src/bool_to_int_with_if.rs new file mode 100644 index 000000000..a4b8cbb0d --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/bool_to_int_with_if.rs @@ -0,0 +1,125 @@ +use rustc_ast::{ExprPrecedence, LitKind}; +use rustc_hir::{Block, ExprKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; + +use clippy_utils::{diagnostics::span_lint_and_then, is_else_clause, source::snippet_block_with_applicability}; +use rustc_errors::Applicability; + +declare_clippy_lint! { + /// ### What it does + /// Instead of using an if statement to convert a bool to an int, + /// this lint suggests using a `from()` function or an `as` coercion. + /// + /// ### Why is this bad? + /// Coercion or `from()` is idiomatic way to convert bool to a number. + /// Both methods are guaranteed to return 1 for true, and 0 for false. + /// + /// See https://doc.rust-lang.org/std/primitive.bool.html#impl-From%3Cbool%3E + /// + /// ### Example + /// ```rust + /// # let condition = false; + /// if condition { + /// 1_i64 + /// } else { + /// 0 + /// }; + /// ``` + /// Use instead: + /// ```rust + /// # let condition = false; + /// i64::from(condition); + /// ``` + /// or + /// ```rust + /// # let condition = false; + /// condition as i64; + /// ``` + #[clippy::version = "1.65.0"] + pub BOOL_TO_INT_WITH_IF, + style, + "using if to convert bool to int" +} +declare_lint_pass!(BoolToIntWithIf => [BOOL_TO_INT_WITH_IF]); + +impl<'tcx> LateLintPass<'tcx> for BoolToIntWithIf { + fn check_expr(&mut self, ctx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) { + if !expr.span.from_expansion() { + check_if_else(ctx, expr); + } + } +} + +fn check_if_else<'tcx>(ctx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) { + if let ExprKind::If(check, then, Some(else_)) = expr.kind + && let Some(then_lit) = int_literal(then) + && let Some(else_lit) = int_literal(else_) + && check_int_literal_equals_val(then_lit, 1) + && check_int_literal_equals_val(else_lit, 0) + { + let mut applicability = Applicability::MachineApplicable; + let snippet = snippet_block_with_applicability(ctx, check.span, "..", None, &mut applicability); + let snippet_with_braces = { + let need_parens = should_have_parentheses(check); + let (left_paren, right_paren) = if need_parens {("(", ")")} else {("", "")}; + format!("{left_paren}{snippet}{right_paren}") + }; + + let ty = ctx.typeck_results().expr_ty(then_lit); // then and else must be of same type + + let suggestion = { + let wrap_in_curly = is_else_clause(ctx.tcx, expr); + let (left_curly, right_curly) = if wrap_in_curly {("{", "}")} else {("", "")}; + format!( + "{left_curly}{ty}::from({snippet}){right_curly}" + ) + }; // when used in else clause if statement should be wrapped in curly braces + + span_lint_and_then(ctx, + BOOL_TO_INT_WITH_IF, + expr.span, + "boolean to int conversion using if", + |diag| { + diag.span_suggestion( + expr.span, + "replace with from", + suggestion, + applicability, + ); + diag.note(format!("`{snippet_with_braces} as {ty}` or `{snippet_with_braces}.into()` can also be valid options")); + }); + }; +} + +// If block contains only a int literal expression, return literal expression +fn int_literal<'tcx>(expr: &'tcx rustc_hir::Expr<'tcx>) -> Option<&'tcx rustc_hir::Expr<'tcx>> { + if let ExprKind::Block(block, _) = expr.kind + && let Block { + stmts: [], // Shouldn't lint if statements with side effects + expr: Some(expr), + .. + } = block + && let ExprKind::Lit(lit) = &expr.kind + && let LitKind::Int(_, _) = lit.node + { + Some(expr) + } else { + None + } +} + +fn check_int_literal_equals_val<'tcx>(expr: &'tcx rustc_hir::Expr<'tcx>, expected_value: u128) -> bool { + if let ExprKind::Lit(lit) = &expr.kind + && let LitKind::Int(val, _) = lit.node + && val == expected_value + { + true + } else { + false + } +} + +fn should_have_parentheses<'tcx>(check: &'tcx rustc_hir::Expr<'tcx>) -> bool { + check.precedence().order() < ExprPrecedence::Cast.order() +} |