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Suggest using a qualified path in patterns with inconsistent bindings #63406

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Aug 12, 2019
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Suggest using a qualified path in patterns with inconsistent bindings #63406

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53a6304
Suggest using a qualified path in patterns with inconsistent bindings
jakubadamw Aug 9, 2019
30db4eb
Apply suggestions from code review
jakubadamw Aug 9, 2019
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21 changes: 16 additions & 5 deletions src/librustc_resolve/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use syntax_pos::{BytePos, Span, MultiSpan};

use crate::resolve_imports::{ImportDirective, ImportDirectiveSubclass, ImportResolver};
use crate::{path_names_to_string, KNOWN_TOOLS};
use crate::{CrateLint, LegacyScope, Module, ModuleOrUniformRoot};
use crate::{BindingError, CrateLint, LegacyScope, Module, ModuleOrUniformRoot};
use crate::{PathResult, ParentScope, ResolutionError, Resolver, Scope, ScopeSet, Segment};

type Res = def::Res<ast::NodeId>;
Expand Down Expand Up @@ -207,21 +207,32 @@ impl<'a> Resolver<'a> {
err
}
ResolutionError::VariableNotBoundInPattern(binding_error) => {
let target_sp = binding_error.target.iter().cloned().collect::<Vec<_>>();
let BindingError { name, target, origin, could_be_path } = binding_error;

let target_sp = target.iter().copied().collect::<Vec<_>>();
let origin_sp = origin.iter().copied().collect::<Vec<_>>();

let msp = MultiSpan::from_spans(target_sp.clone());
let msg = format!("variable `{}` is not bound in all patterns", binding_error.name);
let msg = format!("variable `{}` is not bound in all patterns", name);
let mut err = self.session.struct_span_err_with_code(
msp,
&msg,
DiagnosticId::Error("E0408".into()),
);
for sp in target_sp {
err.span_label(sp, format!("pattern doesn't bind `{}`", binding_error.name));
err.span_label(sp, format!("pattern doesn't bind `{}`", name));
}
let origin_sp = binding_error.origin.iter().cloned();
for sp in origin_sp {
err.span_label(sp, "variable not in all patterns");
}
if *could_be_path {
let help_msg = format!(
"if you meant to match on a variant or a `const` item, consider \
making the path in the pattern qualified: `?::{}`",
name,
);
err.span_help(span, &help_msg);
}
err
}
ResolutionError::VariableBoundWithDifferentMode(variable_name,
Expand Down
86 changes: 38 additions & 48 deletions src/librustc_resolve/late.rs
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Expand Up @@ -1136,65 +1136,53 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
// Checks that all of the arms in an or-pattern have exactly the
// same set of bindings, with the same binding modes for each.
fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) {
if pats.is_empty() {
return;
}

let mut missing_vars = FxHashMap::default();
let mut inconsistent_vars = FxHashMap::default();
for (i, p) in pats.iter().enumerate() {
let map_i = self.binding_mode_map(&p);

for (j, q) in pats.iter().enumerate() {
if i == j {
continue;
}

let map_j = self.binding_mode_map(&q);
for (&key, &binding_i) in &map_i {
if map_j.is_empty() { // Account for missing bindings when
let binding_error = missing_vars // `map_j` has none.
.entry(key.name)
.or_insert(BindingError {
name: key.name,
origin: BTreeSet::new(),
target: BTreeSet::new(),
});
binding_error.origin.insert(binding_i.span);
binding_error.target.insert(q.span);
}
for (&key_j, &binding_j) in &map_j {
match map_i.get(&key_j) {
None => { // missing binding
let binding_error = missing_vars
.entry(key_j.name)
.or_insert(BindingError {
name: key_j.name,
origin: BTreeSet::new(),
target: BTreeSet::new(),
});
binding_error.origin.insert(binding_j.span);
binding_error.target.insert(p.span);
}
Some(binding_i) => { // check consistent binding
if binding_i.binding_mode != binding_j.binding_mode {
inconsistent_vars
.entry(key.name)
.or_insert((binding_j.span, binding_i.span));
}
for pat_outer in pats.iter() {
let map_outer = self.binding_mode_map(&pat_outer);

for pat_inner in pats.iter().filter(|pat| pat.id != pat_outer.id) {
let map_inner = self.binding_mode_map(&pat_inner);

for (&key_inner, &binding_inner) in map_inner.iter() {
match map_outer.get(&key_inner) {
None => { // missing binding
let binding_error = missing_vars
.entry(key_inner.name)
.or_insert(BindingError {
name: key_inner.name,
origin: BTreeSet::new(),
target: BTreeSet::new(),
could_be_path:
key_inner.name.as_str().starts_with(char::is_uppercase)
});
binding_error.origin.insert(binding_inner.span);
binding_error.target.insert(pat_outer.span);
}
Some(binding_outer) => { // check consistent binding
if binding_outer.binding_mode != binding_inner.binding_mode {
inconsistent_vars
.entry(key_inner.name)
.or_insert((binding_inner.span, binding_outer.span));
}
}
}
}
}
}
let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();

let mut missing_vars = missing_vars.iter_mut().collect::<Vec<_>>();
missing_vars.sort();
for (_, v) in missing_vars {
for (name, mut v) in missing_vars {
if inconsistent_vars.contains_key(name) {
v.could_be_path = false;
}
self.r.report_error(
*v.origin.iter().next().unwrap(), ResolutionError::VariableNotBoundInPattern(v)
);
*v.origin.iter().next().unwrap(),
ResolutionError::VariableNotBoundInPattern(v));
}

let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
inconsistent_vars.sort();
for (name, v) in inconsistent_vars {
Expand Down Expand Up @@ -1222,7 +1210,9 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
self.resolve_pattern(pat, source, &mut bindings_list);
}
// This has to happen *after* we determine which pat_idents are variants
self.check_consistent_bindings(pats);
if pats.len() > 1 {
self.check_consistent_bindings(pats);
}
}

fn resolve_block(&mut self, block: &Block) {
Expand Down
1 change: 1 addition & 0 deletions src/librustc_resolve/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,7 @@ struct BindingError {
name: Name,
origin: BTreeSet<Span>,
target: BTreeSet<Span>,
could_be_path: bool
}

impl PartialOrd for BindingError {
Expand Down
31 changes: 30 additions & 1 deletion src/test/ui/resolve/resolve-inconsistent-names.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,36 @@
#![allow(non_camel_case_types)]

enum E { A, B, c }

mod m {
const CONST1: usize = 10;
const Const2: usize = 20;
}

fn main() {
let y = 1;
match y {
a | b => {} //~ ERROR variable `a` is not bound in all patterns
//~^ ERROR variable `b` is not bound in all patterns
//~| ERROR variable `b` is not bound in all patterns
}

let x = (E::A, E::B);
match x {
(A, B) | (ref B, c) | (c, A) => ()
//~^ ERROR variable `A` is not bound in all patterns
//~| ERROR variable `B` is not bound in all patterns
//~| ERROR variable `B` is bound in inconsistent ways
//~| ERROR mismatched types
//~| ERROR variable `c` is not bound in all patterns
//~| HELP consider making the path in the pattern qualified: `?::A`
}

let z = (10, 20);
match z {
(CONST1, _) | (_, Const2) => ()
//~^ ERROR variable `CONST1` is not bound in all patterns
//~| HELP consider making the path in the pattern qualified: `?::CONST1`
//~| ERROR variable `Const2` is not bound in all patterns
//~| HELP consider making the path in the pattern qualified: `?::Const2`
}
}
87 changes: 83 additions & 4 deletions src/test/ui/resolve/resolve-inconsistent-names.stderr
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@@ -1,19 +1,98 @@
error[E0408]: variable `a` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:4:12
--> $DIR/resolve-inconsistent-names.rs:13:12
|
LL | a | b => {}
| - ^ pattern doesn't bind `a`
| |
| variable not in all patterns

error[E0408]: variable `b` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:4:8
--> $DIR/resolve-inconsistent-names.rs:13:8
|
LL | a | b => {}
| ^ - variable not in all patterns
| |
| pattern doesn't bind `b`

error: aborting due to 2 previous errors
error[E0408]: variable `A` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:19:18
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| - ^^^^^^^^^^ - variable not in all patterns
| | |
| | pattern doesn't bind `A`
| variable not in all patterns
|
help: if you meant to match on a variant or a `const` item, consider making the path in the pattern qualified: `?::A`
--> $DIR/resolve-inconsistent-names.rs:19:10
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| ^

error[E0408]: variable `B` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:19:31
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| - - ^^^^^^ pattern doesn't bind `B`
| | |
| | variable not in all patterns
| variable not in all patterns

error[E0408]: variable `c` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:19:9
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| ^^^^^^ - - variable not in all patterns
| | |
| | variable not in all patterns
| pattern doesn't bind `c`

error[E0409]: variable `B` is bound in inconsistent ways within the same match arm
--> $DIR/resolve-inconsistent-names.rs:19:23
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| - ^ bound in different ways
| |
| first binding

error[E0408]: variable `CONST1` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:30:23
|
LL | (CONST1, _) | (_, Const2) => ()
| ------ ^^^^^^^^^^^ pattern doesn't bind `CONST1`
| |
| variable not in all patterns
|
help: if you meant to match on a variant or a `const` item, consider making the path in the pattern qualified: `?::CONST1`
--> $DIR/resolve-inconsistent-names.rs:30:10
|
LL | (CONST1, _) | (_, Const2) => ()
| ^^^^^^

error[E0408]: variable `Const2` is not bound in all patterns
--> $DIR/resolve-inconsistent-names.rs:30:9
|
LL | (CONST1, _) | (_, Const2) => ()
| ^^^^^^^^^^^ ------ variable not in all patterns
| |
| pattern doesn't bind `Const2`
|
help: if you meant to match on a variant or a `const` item, consider making the path in the pattern qualified: `?::Const2`
--> $DIR/resolve-inconsistent-names.rs:30:27
|
LL | (CONST1, _) | (_, Const2) => ()
| ^^^^^^

error[E0308]: mismatched types
--> $DIR/resolve-inconsistent-names.rs:19:19
|
LL | (A, B) | (ref B, c) | (c, A) => ()
| ^^^^^ expected enum `E`, found &E
|
= note: expected type `E`
found type `&E`

error: aborting due to 9 previous errors

For more information about this error, try `rustc --explain E0408`.
Some errors have detailed explanations: E0308, E0408, E0409.
For more information about an error, try `rustc --explain E0308`.