8000 Suggest `_` and `..` if a pattern has too few fields by camelid · Pull Request #80017 · rust-lang/rust · GitHub
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Suggest _ and .. if a pattern has too few fields #80017

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Merged
merged 9 commits into from
Jan 14, 2021
Merged

Suggest _ and .. if a pattern has too few fields #80017

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16692ab
Suggest `_` and `..` if a pattern has too few fields
camelid Dec 13, 2020
5fe61a7
Simplify code
camelid Dec 19, 2020
f3d9df5
Suggest `Variant(..)` if all of the mentioned fields are `_`
camelid Dec 19, 2020
a5e8e6e
Pluralize 'parenthesis' correctly
camelid Dec 19, 2020
fe82cc3
Specialize `..` help message for all fields vs. the rest
camelid Dec 19, 2020
9959d6d
Only suggest `..` if more than one field is missing
camelid Dec 20, 2020
1bce775
Add a test case with lots of whitespace
camelid Jan 13, 2021
d7307a7
Always show suggestions in their own subwindows
camelid Jan 13, 2021
e8c8793
Include `..` suggestion if fields are all wildcards
camelid Jan 13, 2021
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Always show suggestions in their own subwindows
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@camelid
camelid committed Jan 13, 2021
commit d7307a71f5e1893f7bd69ff160ce38dc97b5d195
6 changes: 3 additions & 3 deletions compiler/rustc_typeck/src/check/pat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1061,7 +1061,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
wildcard_sugg = String::from(", ") + &wildcard_sugg;
}

err.span_suggestion_short(
err.span_suggestion_verbose(
after_fields_span,
"use `_` to explicitly ignore each field",
wildcard_sugg,
Expand All @@ -1071,14 +1071,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Only suggest `..` if more than one field is missing.
if fields.len() - subpats.len() > 1 {
if subpats.is_empty() || all_wildcards {
err.span_suggestion_short(
err.span_suggestion_verbose(
all_fields_span,
"use `..` to ignore all fields",
String::from(".."),
Applicability::MaybeIncorrect,
);
} else {
err.span_suggestion_short(
err.span_suggestion_verbose(
after_fields_span,
"use `..` to ignore the rest of the fields",
String::from(", .."),
Expand Down
20 changes: 12 additions & 8 deletions src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.stderr
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Expand Up @@ -30,10 +30,12 @@ LL | struct TupleStruct<S, T>(S, T);
| ------------------------------- tuple struct defined here
...
LL | TupleStruct(_) = TupleStruct(1, 2);
| ^^^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | TupleStruct(_, _) = TupleStruct(1, 2);
| ^^^
Comment on lines +34 to +38
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These two cases should also be suggesting .. as an alternative, no?

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Well, if someone is already explicitly listing out wildcards, should we suggest that they use ..? On the other hand, someone may not know that .. is an option and would rather that over listing out wildcards manually. So I think overall I agree with you that we should be giving it as an alternative :)

I'll change it, but for other things we can always adjust the behavior later; I'm hoping to have this PR finished soon.

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Sounds reasonable, I don't foresee any big changes. I think that the code itself looks good but want to nail down the exact behavior we want.

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So is the behavior you're suggesting that we also suggest S(..) if it's currently of the form S(_, _, _)?

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@estebank estebank Jan 13, 2021 •
edited
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Yes, I think that if it is currently S(_, _) and we suggest S(_, _, _) we should also suggest S(..). Having said that, if you find that it will be too much work, only create a follow-up ticket and r=me.


error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
--> $DIR/tuple_struct_destructure_fail.rs:34:5
Expand All @@ -51,10 +53,12 @@ LL | SingleVariant(S, T)
| ------------------- tuple variant defined here
...
LL | Enum::SingleVariant(_) = Enum::SingleVariant(1, 2);
| ^^^^^^^^^^^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^^^^^^^^^^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | Enum::SingleVariant(_, _) = Enum::SingleVariant(1, 2);
| ^^^

error[E0070]: invalid left-hand side of assignment
--> $DIR/tuple_struct_destructure_fail.rs:40:12
Expand Down
8000
10 changes: 6 additions & 4 deletions src/test/ui/error-codes/E0023.stderr
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Expand Up @@ -5,10 +5,12 @@ LL | Apple(String, String),
| --------------------- tuple variant defined here
...
LL | Fruit::Apple(a) => {},
| ^^^^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^^^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | Fruit::Apple(a, _) => {},
| ^^^

error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
--> $DIR/E0023.rs:12:9
Expand Down
10 changes: 6 additions & 4 deletions src/test/ui/issues/issue-67037-pat-tup-scrut-ty-diff-less-fields.stderr
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Expand Up @@ -16,10 +16,12 @@ LL | struct P<T>(T); // 1 type parameter wanted
| --------------- tuple struct defined here
...
LL | let P() = U {};
| ^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 1 field, found 0
| ^^^ expected 1 field, found 0
|
help: use `_` to explicitly ignore each field
|
LL | let P(_) = U {};
| ^

error: aborting due to 2 previous errors

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10 changes: 6 additions & 4 deletions src/test/ui/issues/issue-72574-2.stderr
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Expand Up @@ -25,10 +25,12 @@ LL | struct Binder(i32, i32, i32);
| ----------------------------- tuple struct defined here
...
LL | Binder(_a, _x @ ..) => {}
| ^^^^^^^^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 3 fields, found 2
| ^^^^^^^^^^^^^^^^^^^ expected 3 fields, found 2
|
help: use `_` to explicitly ignore each field
|
LL | Binder(_a, _x @ .., _) => {}
| ^^^

error: aborting due to 3 previous errors

Expand Down
10 changes: 6 additions & 4 deletions src/test/ui/match/match-pattern-field-mismatch.stderr
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Expand Up @@ -5,10 +5,12 @@ LL | Rgb(usize, usize, usize),
| ------------------------ tuple variant defined here
...
LL | Color::Rgb(_, _) => { }
| ^^^^^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 3 fields, found 2
| ^^^^^^^^^^^^^^^^ expected 3 fields, found 2
|
help: use `_` to explicitly ignore each field
|
LL | Color::Rgb(_, _, _) => { }
| ^^^

error: aborting due to previous error

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10 changes: 6 additions & 4 deletions src/test/ui/pattern/issue-74539.stderr
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Expand Up @@ -25,10 +25,12 @@ LL | A(u8, u8),
| --------- tuple variant defined here
...
LL | E::A(x @ ..) => {
| ^^^^^^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | E::A(x @ .., _) => {
| ^^^

error: aborting due to 3 previous errors

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40 changes: 24 additions & 16 deletions src/test/ui/pattern/pat-tuple-underfield.stderr
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Expand Up @@ -14,10 +14,12 @@ LL | struct S(i32, f32);
| ------------------- tuple struct defined here
...
LL | S(x) => {}
| ^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | S(x, _) => {}
| ^^^

error[E0023]: this pattern has 1 field, but the corresponding tuple struct has 2 fields
--> $DIR/pat-tuple-underfield.rs:14:9
Expand All @@ -26,10 +28,12 @@ LL | struct S(i32, f32);
| ------------------- tuple struct defined here
...
LL | S(_) => {}
| ^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | S(_, _) => {}
| ^^^

error[E0023]: this pattern has 0 fields, but the corresponding tuple struct has 2 fields
--> $DIR/pat-tuple-underfield.rs:19:9
Expand All @@ -56,10 +60,12 @@ LL | S(i32, f32),
| ----------- tuple variant defined here
...
LL | E::S(x) => {}
| ^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | E::S(x, _) => {}
| ^^^

error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
--> $DIR/pat-tuple-underfield.rs:31:9
Expand All @@ -68,10 +74,12 @@ LL | S(i32, f32),
| ----------- tuple variant defined here
...
LL | E::S(_) => {}
| ^^^^^^-
| | |
| | help: use `_` to explicitly ignore each field
| expected 2 fields, found 1
| ^^^^^^^ expected 2 fields, found 1
|
help: use `_` to explicitly ignore each field
|
LL | E::S(_, _) => {}
| ^^^

error[E0023]: this pattern has 0 fields, but the corresponding tuple variant has 2 fields
--> $DIR/pat-tuple-underfield.rs:36:9
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0