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Display correct unused field suggestion for nested struct patterns #50327

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Apr 30, 2018
Merged

Display correct unused field suggestion for nested struct patterns #50327

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cc53db8
Correct unused field warning on &struct match
varkor Apr 29, 2018
8e8fe90
Correct unused field warning on box struct match
varkor Apr 29, 2018
2eb8343
Correct unused field warning on struct match container patterns
varkor Apr 30, 2018
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44 changes: 35 additions & 9 deletions src/librustc/middle/liveness.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,7 @@ use ty::{self, TyCtxt};
use lint;
use util::nodemap::{NodeMap, NodeSet};

use std::collections::VecDeque;
use std::{fmt, usize};
use std::io::prelude::*;
use std::io;
Expand Down Expand Up @@ -412,18 +413,43 @@ fn visit_local<'a, 'tcx>(ir: &mut IrMaps<'a, 'tcx>, local: &'tcx hir::Local) {
}

fn visit_arm<'a, 'tcx>(ir: &mut IrMaps<'a, 'tcx>, arm: &'tcx hir::Arm) {
for pat in &arm.pats {
// for struct patterns, take note of which fields used shorthand (`x` rather than `x: x`)
for mut pat in &arm.pats {
// For struct patterns, take note of which fields used shorthand
// (`x` rather than `x: x`).
//
// FIXME: according to the rust-lang-nursery/rustc-guide book, `NodeId`s are to be phased
// out in favor of `HirId`s; however, we need to match the signature of `each_binding`,
// which uses `NodeIds`.
// FIXME: according to the rust-lang-nursery/rustc-guide book, `NodeId`s are to be
// phased out in favor of `HirId`s; however, we need to match the signature of
// `each_binding`, which uses `NodeIds`.
let mut shorthand_field_ids = NodeSet();
if let hir::PatKind::Struct(_, ref fields, _) = pat.node {
for field in fields {
if field.node.is_shorthand {
shorthand_field_ids.insert(field.node.pat.id);
let mut pats = VecDeque::new();
pats.push_back(pat);
while let Some(pat) = pats.pop_front() {
use hir::PatKind::*;
match pat.node {
Binding(_, _, _, ref inner_pat) => {
pats.extend(inner_pat.iter());
}
Struct(_, ref fields, _) => {
for field in fields {
if field.node.is_shorthand {
shorthand_field_ids.insert(field.node.pat.id);
}
}
}
Ref(ref inner_pat, _) |
Box(ref inner_pat) => {
pats.push_back(inner_pat);
}
TupleStruct(_, ref inner_pats, _) |
Tuple(ref inner_pats, _) => {
pats.extend(inner_pats.iter());
}
Slice(ref pre_pats, ref inner_pat, ref post_pats) => {
pats.extend(pre_pats.iter());
pats.extend(inner_pat.iter());
pats.extend(post_pats.iter());
}
_ => {}
}
}

Expand Down
43 changes: 43 additions & 0 deletions src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@

// compile-pass

#![feature(box_syntax)]
#![feature(box_patterns)]
#![warn(unused)] // UI tests pass `-A unused` (#43896)

struct SoulHistory {
Expand All @@ -18,6 +20,13 @@ struct SoulHistory {
endless_and_singing: bool
}

#[derive(Clone, Copy)]
enum Large {
Suit { case: () }
}

struct Tuple(Large, ());

fn main() {
let i_think_continually = 2;
let who_from_the_womb_remembered = SoulHistory {
Expand All @@ -31,4 +40,38 @@ fn main() {
endless_and_singing: true } = who_from_the_womb_remembered {
hours_are_suns = false;
}

let bag = Large::Suit {
case: ()
};

// Plain struct
match bag {
Large::Suit { case } => {}
};

// Referenced struct
match &bag {
&Large::Suit { case } => {}
};

// Boxed struct
match box bag {
box Large::Suit { case } => {}
};

// Tuple with struct
match (bag,) {
(Large::Suit { case },) => {}
};

// Slice with struct
match [bag] {
[Large::Suit { case }] => {}
};

// Tuple struct with struct
match Tuple(bag, ()) {
Tuple(Large::Suit { case }, ()) => {}
};
}
48 changes: 42 additions & 6 deletions src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr
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Original file line number Diff line number Diff line change
@@ -1,40 +1,76 @@
warning: unused variable: `i_think_continually`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:22:9
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:31:9
|
LL | let i_think_continually = 2;
| ^^^^^^^^^^^^^^^^^^^ help: consider using `_i_think_continually` instead
|
note: lint level defined here
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:13:9
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:15:9
|
LL | #![warn(unused)] // UI tests pass `-A unused` (#43896)
| ^^^^^^
= note: #[warn(unused_variables)] implied by #[warn(unused)]

warning: unused variable: `corridors_of_light`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:29:26
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:38:26
|
LL | if let SoulHistory { corridors_of_light,
| ^^^^^^^^^^^^^^^^^^ help: try ignoring the field: `corridors_of_light: _`

warning: variable `hours_are_suns` is assigned to, but never used
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:30:26
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:39:26
|
LL | mut hours_are_suns,
| ^^^^^^^^^^^^^^^^^^
|
= note: consider using `_hours_are_suns` instead

warning: value assigned to `hours_are_suns` is never read
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:32:9
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:41:9
|
LL | hours_are_suns = false;
| ^^^^^^^^^^^^^^
|
note: lint level defined here
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:13:9
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:15:9
|
LL | #![warn(unused)] // UI tests pass `-A unused` (#43896)
| ^^^^^^
= note: #[warn(unused_assignments)] implied by #[warn(unused)]

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:50:23
|
LL | Large::Suit { case } => {}
| ^^^^ help: try ignoring the field: `case: _`

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:55:24
|
LL | &Large::Suit { case } => {}
| ^^^^ help: try ignoring the field: `case: _`

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:60:27
|
LL | box Large::Suit { case } => {}
| ^^^^ help: try ignoring the field: `case: _`

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:65:24
|
LL | (Large::Suit { case },) => {}
| ^^^^ help: try ignoring the field: `case: _`

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:70:24
|
LL | [Large::Suit { case }] => {}
| ^^^^ help: try ignoring the field: `case: _`

warning: unused variable: `case`
--> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:75:29
|
LL | Tuple(Large::Suit { case }, ()) => {}
| ^^^^ help: try ignoring the field: `case: _`