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Unused variable suggestions on all patterns.

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This commit extends existing suggestions to prefix unused variable
bindings in match arms with an underscore so that it applies to all
patterns in a match arm.
This commit is contained in:
David Wood 2019-01-25 16:56:27 +01:00
parent c32515566f
commit 5f021e0023
No known key found for this signature in database
GPG key ID: 01760B4F9F53F154
17 changed files with 179 additions and 59 deletions
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84
src/librustc/middle/liveness.rs
View file

@ -105,7 +105,7 @@ use lint;
use errors::Applicability;
use util::nodemap::{NodeMap, HirIdMap, HirIdSet};
use std::collections::VecDeque;
use std::collections::{BTreeMap, VecDeque};
use std::{fmt, u32};
use std::io::prelude::*;
use std::io;
@ -1446,7 +1446,7 @@ fn check_local<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, local: &'tcx hir::Local)
None => {
this.pat_bindings(&local.pat, |this, ln, var, sp, id| {
let span = local.pat.simple_ident().map_or(sp, |ident| ident.span);
this.warn_about_unused(span, id, ln, var);
this.warn_about_unused(vec![span], id, ln, var);
})
}
}
@ -1455,12 +1455,29 @@ fn check_local<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, local: &'tcx hir::Local)
}
fn check_arm<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, arm: &'tcx hir::Arm) {
// only consider the first pattern; any later patterns must have
// the same bindings, and we also consider the first pattern to be
// the "authoritative" set of ids
this.arm_pats_bindings(arm.pats.first().map(|p| &**p), |this, ln, var, sp, id| {
this.warn_about_unused(sp, id, ln, var);
});
// Only consider the variable from the first pattern; any later patterns must have
// the same bindings, and we also consider the first pattern to be the "authoritative" set of
// ids. However, we should take the spans of variables with the same name from the later
// patterns so the suggestions to prefix with underscores will apply to those too.
let mut vars: BTreeMap<String, (LiveNode, Variable, HirId, Vec<Span>)> = Default::default();
for pat in &arm.pats {
this.arm_pats_bindings(Some(&*pat), |this, ln, var, sp, id| {
let name = this.ir.variable_name(var);
vars.entry(name)
.and_modify(|(.., spans)| {
spans.push(sp);
})
.or_insert_with(|| {
(ln, var, id, vec![sp])
});
});
}
for (_, (ln, var, id, spans)) in vars {
this.warn_about_unused(spans, id, ln, var);
}
intravisit::walk_arm(this, arm);
}
@ -1551,7 +1568,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
let var = self.variable(hir_id, sp);
// Ignore unused self.
if ident.name != keywords::SelfLower.name() {
if !self.warn_about_unused(sp, hir_id, entry_ln, var) {
if !self.warn_about_unused(vec![sp], hir_id, entry_ln, var) {
if self.live_on_entry(entry_ln, var).is_none() {
self.report_dead_assign(hir_id, sp, var, true);
}
@ -1563,14 +1580,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
fn warn_about_unused_or_dead_vars_in_pat(&mut self, pat: &hir::Pat) {
self.pat_bindings(pat, |this, ln, var, sp, id| {
if !this.warn_about_unused(sp, id, ln, var) {
if !this.warn_about_unused(vec![sp], id, ln, var) {
this.warn_about_dead_assign(sp, id, ln, var);
}
})
}
fn warn_about_unused(&self,
sp: Span,
spans: Vec<Span>,
hir_id: HirId,
ln: LiveNode,
var: Variable)
@ -1587,33 +1604,36 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
self.assigned_on_exit(ln, var).is_some()
};
let suggest_underscore_msg = format!("consider using `_{}` instead", name);
if is_assigned {
self.ir.tcx
.lint_hir_note(lint::builtin::UNUSED_VARIABLES, hir_id, sp,
&format!("variable `{}` is assigned to, but never used",
name),
&suggest_underscore_msg);
self.ir.tcx.lint_hir_note(
lint::builtin::UNUSED_VARIABLES,
hir_id,
spans.clone(),
&format!("variable `{}` is assigned to, but never used", name),
&format!("consider using `_{}` instead", name),
);
} else if name != "self" {
let msg = format!("unused variable: `{}`", name);
let mut err = self.ir.tcx
.struct_span_lint_hir(lint::builtin::UNUSED_VARIABLES, hir_id, sp, &msg);
let mut err = self.ir.tcx.struct_span_lint_hir(
lint::builtin::UNUSED_VARIABLES,
hir_id,
spans.clone(),
&format!("unused variable: `{}`", name),
);
if self.ir.variable_is_shorthand(var) {
err.span_suggestion(
sp,
err.multipart_suggestion(
"try ignoring the field",
format!("{}: _", name),
Applicability::MachineApplicable,
spans.iter().map(|span| (*span, format!("{}: _", name))).collect(),
Applicability::MachineApplicable
);
} else {
err.span_suggestion_short(
sp,
&suggest_underscore_msg,
format!("_{}", name),
err.multipart_suggestion(
"consider prefixing with an underscore",
spans.iter().map(|span| (*span, format!("_{}", name))).collect(),
Applicability::MachineApplicable,
);
}
err.emit()
}
}
@ -1623,11 +1643,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
}
}
fn warn_about_dead_assign(&self,
sp: Span,
hir_id: HirId,
ln: LiveNode,
var: Variable) {
fn warn_about_dead_assign(&self, sp: Span, hir_id: HirId, ln: LiveNode, var: Variable) {
if self.live_on_exit(ln, var).is_none() {
self.report_dead_assign(hir_id, sp, var, false);
}

4
src/test/ui/issues/issue-17999.stderr
View file

@ -2,7 +2,7 @@ error: unused variable: `x`
--> $DIR/issue-17999.rs:5:13
|
LL | let x = (); //~ ERROR: unused variable: `x`
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
|
note: lint level defined here
--> $DIR/issue-17999.rs:1:9
@ -14,7 +14,7 @@ error: unused variable: `a`
--> $DIR/issue-17999.rs:7:13
|
LL | a => {} //~ ERROR: unused variable: `a`
| ^ help: consider using `_a` instead
| ^ help: consider prefixing with an underscore: `_a`
error: aborting due to 2 previous errors

2
src/test/ui/issues/issue-22599.stderr
View file

@ -2,7 +2,7 @@ error: unused variable: `a`
--> $DIR/issue-22599.rs:8:19
|
LL | v = match 0 { a => 0 }; //~ ERROR: unused variable: `a`
| ^ help: consider using `_a` instead
| ^ help: consider prefixing with an underscore: `_a`
|
note: lint level defined here
--> $DIR/issue-22599.rs:1:9

44
src/test/ui/issues/issue-56685.rs Normal file
View file

@ -0,0 +1,44 @@
#![allow(dead_code)]
#![deny(unused_variables)]
// This test aims to check that unused variable suggestions update bindings in all
// match arms.
fn main() {
enum E {
A(i32,),
B(i32,),
}
match E::A(1) {
E::A(x) | E::B(x) => {}
//~^ ERROR unused variable: `x`
}
enum F {
A(i32, i32,),
B(i32, i32,),
C(i32, i32,),
}
let _ = match F::A(1, 2) {
F::A(x, y) | F::B(x, y) => { y },
//~^ ERROR unused variable: `x`
F::C(a, b) => { 3 }
//~^ ERROR unused variable: `a`
//~^^ ERROR unused variable: `b`
};
let _ = if let F::A(x, y) | F::B(x, y) = F::A(1, 2) {
//~^ ERROR unused variable: `x`
y
} else {
3
};
while let F::A(x, y) | F::B(x, y) = F::A(1, 2) {
//~^ ERROR unused variable: `x`
let _ = y;
break;
}
}

60
src/test/ui/issues/issue-56685.stderr Normal file
View file

@ -0,0 +1,60 @@
error: unused variable: `x`
--> $DIR/issue-56685.rs:14:14
|
LL | E::A(x) | E::B(x) => {}
| ^ ^
|
note: lint level defined here
--> $DIR/issue-56685.rs:2:9
|
LL | #![deny(unused_variables)]
| ^^^^^^^^^^^^^^^^
help: consider prefixing with an underscore
|
LL | E::A(_x) | E::B(_x) => {}
| ^^ ^^
error: unused variable: `x`
--> $DIR/issue-56685.rs:25:14
|
LL | F::A(x, y) | F::B(x, y) => { y },
| ^ ^
help: consider prefixing with an underscore
|
LL | F::A(_x, y) | F::B(_x, y) => { y },
| ^^ ^^
error: unused variable: `a`
--> $DIR/issue-56685.rs:27:14
|
LL | F::C(a, b) => { 3 }
| ^ help: consider prefixing with an underscore: `_a`
error: unused variable: `b`
--> $DIR/issue-56685.rs:27:17
|
LL | F::C(a, b) => { 3 }
| ^ help: consider prefixing with an underscore: `_b`
error: unused variable: `x`
--> $DIR/issue-56685.rs:32:25
|
LL | let _ = if let F::A(x, y) | F::B(x, y) = F::A(1, 2) {
| ^ ^
help: consider prefixing with an underscore
|
LL | let _ = if let F::A(_x, y) | F::B(_x, y) = F::A(1, 2) {
| ^^ ^^
error: unused variable: `x`
--> $DIR/issue-56685.rs:39:20
|
LL | while let F::A(x, y) | F::B(x, y) = F::A(1, 2) {
| ^ ^
help: consider prefixing with an underscore
|
LL | while let F::A(_x, y) | F::B(_x, y) = F::A(1, 2) {
| ^^ ^^
error: aborting due to 6 previous errors

8
src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr
View file

@ -2,7 +2,7 @@ warning: unused variable: `i_think_continually`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:26:9
|
LL | let i_think_continually = 2;
| ^^^^^^^^^^^^^^^^^^^ help: consider using `_i_think_continually` instead
| ^^^^^^^^^^^^^^^^^^^ help: consider prefixing with an underscore: `_i_think_continually`
|
note: lint level defined here
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:5:9
@ -15,19 +15,19 @@ warning: unused variable: `mut_unused_var`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:33:13
|
LL | let mut mut_unused_var = 1;
| ^^^^^^^^^^^^^^ help: consider using `_mut_unused_var` instead
| ^^^^^^^^^^^^^^ help: consider prefixing with an underscore: `_mut_unused_var`
warning: unused variable: `var`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:35:14
|
LL | let (mut var, unused_var) = (1, 2);
| ^^^ help: consider using `_var` instead
| ^^^ help: consider prefixing with an underscore: `_var`
warning: unused variable: `unused_var`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:35:19
|
LL | let (mut var, unused_var) = (1, 2);
| ^^^^^^^^^^ help: consider using `_unused_var` instead
| ^^^^^^^^^^ help: consider prefixing with an underscore: `_unused_var`
warning: unused variable: `corridors_of_light`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:26

2
src/test/ui/lint/lint-removed-allow.stderr
View file

@ -2,7 +2,7 @@ error: unused variable: `unused`
--> $DIR/lint-removed-allow.rs:8:17
|
LL | fn main() { let unused = (); } //~ ERROR unused
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-removed-allow.rs:7:8

2
src/test/ui/lint/lint-removed-cmdline.stderr
View file

@ -6,7 +6,7 @@ error: unused variable: `unused`
--> $DIR/lint-removed-cmdline.rs:12:17
|
LL | fn main() { let unused = (); }
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-removed-cmdline.rs:11:8

2
src/test/ui/lint/lint-removed.stderr
View file

@ -10,7 +10,7 @@ error: unused variable: `unused`
--> $DIR/lint-removed.rs:8:17
|
LL | fn main() { let unused = (); } //~ ERROR unused
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-removed.rs:7:8

2
src/test/ui/lint/lint-renamed-allow.stderr
View file

@ -2,7 +2,7 @@ error: unused variable: `unused`
--> $DIR/lint-renamed-allow.rs:8:17
|
LL | fn main() { let unused = (); } //~ ERROR unused
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-renamed-allow.rs:7:8

2
src/test/ui/lint/lint-renamed-cmdline.stderr
View file

@ -6,7 +6,7 @@ error: unused variable: `unused`
--> $DIR/lint-renamed-cmdline.rs:8:17
|
LL | fn main() { let unused = (); }
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-renamed-cmdline.rs:7:8

2
src/test/ui/lint/lint-renamed.stderr
View file

@ -10,7 +10,7 @@ error: unused variable: `unused`
--> $DIR/lint-renamed.rs:4:17
|
LL | fn main() { let unused = (); } //~ ERROR unused
| ^^^^^^ help: consider using `_unused` instead
| ^^^^^^ help: consider prefixing with an underscore: `_unused`
|
note: lint level defined here
--> $DIR/lint-renamed.rs:3:8

2
src/test/ui/lint/lint-uppercase-variables.stderr
View file

@ -8,7 +8,7 @@ warning: unused variable: `Foo`
--> $DIR/lint-uppercase-variables.rs:22:9
|
LL | Foo => {}
| ^^^ help: consider using `_Foo` instead
| ^^^ help: consider prefixing with an underscore: `_Foo`
|
note: lint level defined here
--> $DIR/lint-uppercase-variables.rs:1:9

16
src/test/ui/liveness/liveness-unused.stderr
View file

@ -15,7 +15,7 @@ error: unused variable: `x`
--> $DIR/liveness-unused.rs:8:7
|
LL | fn f1(x: isize) {
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
|
note: lint level defined here
--> $DIR/liveness-unused.rs:2:9
@ -27,19 +27,19 @@ error: unused variable: `x`
--> $DIR/liveness-unused.rs:12:8
|
LL | fn f1b(x: &mut isize) {
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: unused variable: `x`
--> $DIR/liveness-unused.rs:20:9
|
LL | let x: isize;
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: unused variable: `x`
--> $DIR/liveness-unused.rs:25:9
|
LL | let x = 3;
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: variable `x` is assigned to, but never used
--> $DIR/liveness-unused.rs:30:13
@ -74,25 +74,25 @@ error: unused variable: `i`
--> $DIR/liveness-unused.rs:59:12
|
LL | Some(i) => {
| ^ help: consider using `_i` instead
| ^ help: consider prefixing with an underscore: `_i`
error: unused variable: `x`
--> $DIR/liveness-unused.rs:79:9
|
LL | for x in 1..10 { }
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: unused variable: `x`
--> $DIR/liveness-unused.rs:84:10
|
LL | for (x, _) in [1, 2, 3].iter().enumerate() { }
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: unused variable: `x`
--> $DIR/liveness-unused.rs:89:13
|
LL | for (_, x) in [1, 2, 3].iter().enumerate() {
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
error: variable `x` is assigned to, but never used
--> $DIR/liveness-unused.rs:112:9

2
src/test/ui/never-assign-dead-code.stderr
View file

@ -21,7 +21,7 @@ warning: unused variable: `x`
--> $DIR/never-assign-dead-code.rs:9:9
|
LL | let x: ! = panic!("aah"); //~ WARN unused
| ^ help: consider using `_x` instead
| ^ help: consider prefixing with an underscore: `_x`
|
note: lint level defined here
--> $DIR/never-assign-dead-code.rs:5:9

2
src/test/ui/proc-macro/attributes-included.stderr
View file

@ -2,7 +2,7 @@ warning: unused variable: `a`
--> $DIR/attributes-included.rs:17:9
|
LL | let a: i32 = "foo"; //~ WARN: unused variable
| ^ help: consider using `_a` instead
| ^ help: consider prefixing with an underscore: `_a`
|
note: lint level defined here
--> $DIR/attributes-included.rs:4:9

2
src/test/ui/span/issue-24690.stderr
View file

@ -2,7 +2,7 @@ warning: unused variable: `theOtherTwo`
--> $DIR/issue-24690.rs:13:9
|
LL | let theOtherTwo = 2; //~ WARN should have a snake case name
| ^^^^^^^^^^^ help: consider using `_theOtherTwo` instead
| ^^^^^^^^^^^ help: consider prefixing with an underscore: `_theOtherTwo`
|
note: lint level defined here
--> $DIR/issue-24690.rs:8:9