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Auto merge of #4883 - krishna-veerareddy:issue-4818-cast-sign-loss-false-positive, r=flip1995 

Fix false positive with cast_sign_loss lint

`cast_sign_loss` lint incorrectly suggests that the result of `checked_abs`, `rem_euclid` and `checked_rem_euclid` cannot be casted to an unsigned integer without loss.

Fixes #4818 #4764 #4743

changelog: Fix false positives in `cast_sign_loss` lint
This commit is contained in:
bors 2019-12-12 00:34:59 +00:00
parent 221bf650f6 c0fb74baf5
commit d82debbd01
2 changed files with 64 additions and 10 deletions
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29
clippy_lints/src/types.rs
View File

@ -26,8 +26,9 @@ use crate::consts::{constant, Constant};
use crate::utils::paths;
use crate::utils::{
clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
match_path, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt, snippet_with_applicability,
snippet_with_macro_callsite, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
match_path, method_chain_args, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt,
snippet_with_applicability, snippet_with_macro_callsite, span_help_and_lint, span_lint, span_lint_and_sugg,
span_lint_and_then, unsext,
};
declare_clippy_lint! {
@ -1021,14 +1022,22 @@ fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_fro
}
}
// don't lint for the result of `abs`
// `abs` is an inherent impl of `i{N}`, so a method call with ident `abs` will always
// resolve to that spesific method
if_chain! {
if let ExprKind::MethodCall(ref path, _, _) = op.kind;
if path.ident.name.as_str() == "abs";
then {
return
// don't lint for the result of methods that always return non-negative values
if let ExprKind::MethodCall(ref path, _, _) = op.kind {
let mut method_name = path.ident.name.as_str();
let whitelisted_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
if_chain! {
if method_name == "unwrap";
if let Some(arglist) = method_chain_args(op, &["unwrap"]);
if let ExprKind::MethodCall(ref inner_path, _, _) = &arglist[0][0].kind;
then {
method_name = inner_path.ident.name.as_str();
}
}
if whitelisted_methods.iter().any(|&name| method_name == name) {
return;
}
}

45
tests/ui/cast.rs
View File

@ -42,9 +42,54 @@ fn main() {
i32::max_value() as u32;
i64::max_value() as u64;
i128::max_value() as u128;
(-1i8).abs() as u8;
(-1i16).abs() as u16;
(-1i32).abs() as u32;
(-1i64).abs() as u64;
(-1isize).abs() as usize;
(-1i8).checked_abs().unwrap() as u8;
(-1i16).checked_abs().unwrap() as u16;
(-1i32).checked_abs().unwrap() as u32;
(-1i64).checked_abs().unwrap() as u64;
(-1isize).checked_abs().unwrap() as usize;
(-1i8).rem_euclid(1i8) as u8;
(-1i8).rem_euclid(1i8) as u16;
(-1i16).rem_euclid(1i16) as u16;
(-1i16).rem_euclid(1i16) as u32;
(-1i32).rem_euclid(1i32) as u32;
(-1i32).rem_euclid(1i32) as u64;
(-1i64).rem_euclid(1i64) as u64;
(-1i64).rem_euclid(1i64) as u128;
(-1isize).rem_euclid(1isize) as usize;
(1i8).rem_euclid(-1i8) as u8;
(1i8).rem_euclid(-1i8) as u16;
(1i16).rem_euclid(-1i16) as u16;
(1i16).rem_euclid(-1i16) as u32;
(1i32).rem_euclid(-1i32) as u32;
(1i32).rem_euclid(-1i32) as u64;
(1i64).rem_euclid(-1i64) as u64;
(1i64).rem_euclid(-1i64) as u128;
(1isize).rem_euclid(-1isize) as usize;
(-1i8).checked_rem_euclid(1i8).unwrap() as u8;
(-1i8).checked_rem_euclid(1i8).unwrap() as u16;
(-1i16).checked_rem_euclid(1i16).unwrap() as u16;
(-1i16).checked_rem_euclid(1i16).unwrap() as u32;
(-1i32).checked_rem_euclid(1i32).unwrap() as u32;
(-1i32).checked_rem_euclid(1i32).unwrap() as u64;
(-1i64).checked_rem_euclid(1i64).unwrap() as u64;
(-1i64).checked_rem_euclid(1i64).unwrap() as u128;
(-1isize).checked_rem_euclid(1isize).unwrap() as usize;
(1i8).checked_rem_euclid(-1i8).unwrap() as u8;
(1i8).checked_rem_euclid(-1i8).unwrap() as u16;
(1i16).checked_rem_euclid(-1i16).unwrap() as u16;
(1i16).checked_rem_euclid(-1i16).unwrap() as u32;
(1i32).checked_rem_euclid(-1i32).unwrap() as u32;
(1i32).checked_rem_euclid(-1i32).unwrap() as u64;
(1i64).checked_rem_euclid(-1i64).unwrap() as u64;
(1i64).checked_rem_euclid(-1i64).unwrap() as u128;
(1isize).checked_rem_euclid(-1isize).unwrap() as usize;
}