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Auto merge of #4418 - euclio:byte-lit-suggestion, r=flip1995

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use a structured suggestion for char-lit-as-u8

changelog: use a structured suggestion for char-lit-as-u8
This commit is contained in:
bors 2019-09-04 13:33:47 +00:00
commit 9d2772207e
7 changed files with 89 additions and 25 deletions
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46
clippy_lints/src/types.rs
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@ -15,7 +15,7 @@ use rustc::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
use rustc_errors::Applicability;
use rustc_target::spec::abi::Abi;
use rustc_typeck::hir_ty_to_ty;
use syntax::ast::{FloatTy, IntTy, UintTy};
use syntax::ast::{FloatTy, IntTy, LitIntType, LitKind, UintTy};
use syntax::errors::DiagnosticBuilder;
use syntax::source_map::Span;
use syntax::symbol::sym;
@ -1122,7 +1122,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
if let ExprKind::Lit(ref lit) = ex.node {
use syntax::ast::{LitIntType, LitKind};
if let LitKind::Int(n, _) = lit.node {
if cast_to.is_floating_point() {
let from_nbits = 128 - n.leading_zeros();
@ -1487,29 +1486,40 @@ declare_clippy_lint! {
/// ```
pub CHAR_LIT_AS_U8,
complexity,
"casting a character literal to u8"
"casting a character literal to u8 truncates"
}
declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
use syntax::ast::LitKind;
if_chain! {
if !expr.span.from_expansion();
if let ExprKind::Cast(e, _) = &expr.node;
if let ExprKind::Lit(l) = &e.node;
if let LitKind::Char(c) = l.node;
if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty;
then {
let mut applicability = Applicability::MachineApplicable;
let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
if let ExprKind::Cast(ref e, _) = expr.node {
if let ExprKind::Lit(ref l) = e.node {
if let LitKind::Char(_) = l.node {
if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !expr.span.from_expansion() {
let msg = "casting character literal to u8. `char`s \
are 4 bytes wide in rust, so casting to u8 \
truncates them";
let help = format!(
"Consider using a byte literal instead:\nb{}",
snippet(cx, e.span, "'x'")
);
span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
}
}
span_lint_and_then(
cx,
CHAR_LIT_AS_U8,
expr.span,
"casting a character literal to `u8` truncates",
|db| {
db.note("`char` is four bytes wide, but `u8` is a single byte");
if c.is_ascii() {
db.span_suggestion(
expr.span,
"use a byte literal instead",
format!("b{}", snippet),
applicability,
);
}
});
}
}
}

2
src/lintlist/mod.rs
View File

@ -171,7 +171,7 @@ pub const ALL_LINTS: [Lint; 313] = [
Lint {
name: "char_lit_as_u8",
group: "complexity",
desc: "casting a character literal to u8",
desc: "casting a character literal to u8 truncates",
deprecation: None,
module: "types",
},

4
tests/ui/char_lit_as_u8.rs
View File

@ -1,5 +1,5 @@
#![warn(clippy::char_lit_as_u8)]
#![allow(unused_variables)]
fn main() {
let c = 'a' as u8;
let _ = '❤' as u8; // no suggestion, since a byte literal won't work.
}

7
tests/ui/char_lit_as_u8.stderr
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@ -1,12 +1,11 @@
error: casting character literal to u8. `char`s are 4 bytes wide in rust, so casting to u8 truncates them
error: casting a character literal to `u8` truncates
--> $DIR/char_lit_as_u8.rs:4:13
|
LL | let c = 'a' as u8;
LL | let _ = '❤' as u8; // no suggestion, since a byte literal won't work.
| ^^^^^^^^^
|
= note: `-D clippy::char-lit-as-u8` implied by `-D warnings`
= help: Consider using a byte literal instead:
b'a'
= note: `char` is four bytes wide, but `u8` is a single byte
error: aborting due to previous error

10
tests/ui/char_lit_as_u8_suggestions.fixed Normal file
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@ -0,0 +1,10 @@
// run-rustfix
#![warn(clippy::char_lit_as_u8)]
fn main() {
let _ = b'a';
let _ = b'\n';
let _ = b'\0';
let _ = b'\x01';
}

10
tests/ui/char_lit_as_u8_suggestions.rs Normal file
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@ -0,0 +1,10 @@
// run-rustfix
#![warn(clippy::char_lit_as_u8)]
fn main() {
let _ = 'a' as u8;
let _ = '\n' as u8;
let _ = '\0' as u8;
let _ = '\x01' as u8;
}

35
tests/ui/char_lit_as_u8_suggestions.stderr Normal file
View File

@ -0,0 +1,35 @@
error: casting a character literal to `u8` truncates
--> $DIR/char_lit_as_u8_suggestions.rs:6:13
|
LL | let _ = 'a' as u8;
| ^^^^^^^^^ help: use a byte literal instead: `b'a'`
|
= note: `-D clippy::char-lit-as-u8` implied by `-D warnings`
= note: `char` is four bytes wide, but `u8` is a single byte
error: casting a character literal to `u8` truncates
--> $DIR/char_lit_as_u8_suggestions.rs:7:13
|
LL | let _ = '/n' as u8;
| ^^^^^^^^^^ help: use a byte literal instead: `b'/n'`
|
= note: `char` is four bytes wide, but `u8` is a single byte
error: casting a character literal to `u8` truncates
--> $DIR/char_lit_as_u8_suggestions.rs:8:13
|
LL | let _ = '/0' as u8;
| ^^^^^^^^^^ help: use a byte literal instead: `b'/0'`
|
= note: `char` is four bytes wide, but `u8` is a single byte
error: casting a character literal to `u8` truncates
--> $DIR/char_lit_as_u8_suggestions.rs:9:13
|
LL | let _ = '/x01' as u8;
| ^^^^^^^^^^^^ help: use a byte literal instead: `b'/x01'`
|
= note: `char` is four bytes wide, but `u8` is a single byte
error: aborting due to 4 previous errors