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Better binding name on Err for note

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This commit is contained in:
ThibsG 2020-01-10 10:56:09 +01:00
parent f79c47f28d
commit e5c9073f9c
2 changed files with 37 additions and 27 deletions
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62
clippy_lints/src/matches.rs
View File

@ -17,6 +17,7 @@ use rustc_hir::*;
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
use rustc_span::symbol::Ident;
use std::cmp::Ordering;
use std::collections::Bound;
use syntax::ast::{self, LitKind};
@ -470,18 +471,13 @@ fn is_wild<'tcx>(pat: &impl std::ops::Deref<Target = Pat<'tcx>>) -> bool {
}
}
fn is_unused_underscored<'tcx>(patkind: &'tcx PatKind<'_>, body: &'tcx Expr<'_>) -> bool {
match patkind {
PatKind::Binding(.., ident, None) if ident.as_str().starts_with('_') => {
let mut visitor = UsedVisitor {
var: ident.name,
used: false,
};
walk_expr(&mut visitor, body);
!visitor.used
},
_ => false,
}
fn is_unused<'tcx>(ident: &'tcx Ident, body: &'tcx Expr<'_>) -> bool {
let mut visitor = UsedVisitor {
var: ident.name,
used: false,
};
walk_expr(&mut visitor, body);
!visitor.used
}
struct UsedVisitor {
@ -511,20 +507,34 @@ fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>])
for arm in arms {
if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
let path_str = print::to_string(print::NO_ANN, |s| s.print_qpath(path, false));
if_chain! {
if path_str == "Err";
if inner.iter().any(is_wild) || inner.iter().any(|pat| is_unused_underscored(&pat.kind, arm.body));
if let ExprKind::Block(ref block, _) = arm.body.kind;
if is_panic_block(block);
then {
// `Err(_)` arm with `panic!` found
span_note_and_lint(cx,
MATCH_WILD_ERR_ARM,
arm.pat.span,
"`Err(_)` will match all errors, maybe not a good idea",
arm.pat.span,
"to remove this warning, match each error separately \
or use `unreachable!` macro");
if path_str == "Err" {
let mut matching_wild = inner.iter().any(is_wild);
let mut ident_bind_name = String::from("_");
if !matching_wild {
// Looking for unused bindings (i.e.: `_e`)
inner.iter().for_each(|pat| {
if let PatKind::Binding(.., ident, None) = &pat.kind {
if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
ident_bind_name = (&ident.name.as_str()).to_string();
matching_wild = true;
}
}
});
}
if_chain! {
if matching_wild;
if let ExprKind::Block(ref block, _) = arm.body.kind;
if is_panic_block(block);
then {
// `Err(_)` or `Err(_e)` arm with `panic!` found
span_note_and_lint(cx,
MATCH_WILD_ERR_ARM,
arm.pat.span,
&format!("`Err({})` will match all errors, maybe not a good idea", &ident_bind_name),
arm.pat.span,
"to remove this warning, match each error separately \
or use `unreachable!` macro");
}
}
}
}

2
tests/ui/matches.stderr
View File

@ -78,7 +78,7 @@ LL | Ok(3) => println!("ok"),
| ^^^^^
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: `Err(_)` will match all errors, maybe not a good idea
error: `Err(_e)` will match all errors, maybe not a good idea
--> $DIR/matches.rs:34:9
|
LL | Err(_e) => panic!(),