43 lines
1.4 KiB
Rust
43 lines
1.4 KiB
Rust
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use rustc_ast::LitKind;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::LateContext;
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use rustc_middle::ty::{self, UintTy};
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use if_chain::if_chain;
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use crate::utils::{snippet_with_applicability, span_lint_and_then};
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use super::CHAR_LIT_AS_U8;
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pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::Cast(e, _) = &expr.kind;
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if let ExprKind::Lit(l) = &e.kind;
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if let LitKind::Char(c) = l.node;
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if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(expr).kind();
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then {
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let mut applicability = Applicability::MachineApplicable;
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let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
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span_lint_and_then(
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cx,
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CHAR_LIT_AS_U8,
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expr.span,
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"casting a character literal to `u8` truncates",
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|diag| {
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diag.note("`char` is four bytes wide, but `u8` is a single byte");
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if c.is_ascii() {
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diag.span_suggestion(
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expr.span,
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"use a byte literal instead",
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format!("b{}", snippet),
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applicability,
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);
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}
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});
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}
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}
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}
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