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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()
}
|
