bjoernager/rust
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Rollup merge of #82287 - r00ster91:field_name_and, r=petrochenkov

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Make "missing field" error message more natural

```rust
struct A {
    x: i32,
    y: i32,
    z: i32,
}

fn main() {
    A { };
}
```
```
error[E0063]: missing fields `x`, `y`, `z` in initializer of `A`
 --> src/main.rs:8:5
  |
8 |     A { };
  |     ^ missing `x`, `y`, `z`
```
This error is now:
```
error[E0063]: missing fields `x`, `y` and `z` in initializer of `A`
 --> src/main.rs:8:5
  |
8 |     A { };
  |     ^ missing `x`, `y` and `z`
```
I thought it looked nicer and more natural this way. Also, if there is >3 fields missing, there is an "and" as well ("missing \`x\`, \`y\`, \`z\` *and* 1 other field"), but for <=3 there is not. As such it improves consistency too.

As for the implementation, originally I ended up with a chunky `push_str` algorithm but then I figured I could just do the formatting manually since it's just 3 field names at maximum. It is comparatively readable.

As a sidenote, one thing I was wondering about is, isn't there more cases where you have a list of things like field names? Maybe this whole thing can at some point later be made into a more general function to be used in multiple areas.
This commit is contained in:
Yuki Okushi 2021-02-22 18:26:07 +09:00 • committed by GitHub
commit 20c1fa1770
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9 changed files with 29 additions and 26 deletions
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31
compiler/rustc_typeck/src/check/expr.rs
View file

@ -1348,7 +1348,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
span: Span,
remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
) {
let tcx = self.tcx;
let len = remaining_fields.len();
let mut displayable_field_names =
@ -1356,25 +1355,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
displayable_field_names.sort();
let truncated_fields_error = if len <= 3 {
String::new()
} else {
format!(" and {} other field{}", (len - 3), if len - 3 == 1 { "" } else { "s" })
let mut truncated_fields_error = String::new();
let remaining_fields_names = match &displayable_field_names[..] {
[field1] => format!("`{}`", field1),
[field1, field2] => format!("`{}` and `{}`", field1, field2),
[field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
_ => {
truncated_fields_error =
format!(" and {} other field{}", len - 3, pluralize!(len - 3));
displayable_field_names
.iter()
.take(3)
.map(|n| format!("`{}`", n))
.collect::<Vec<_>>()
.join(", ")
}
};
let remaining_fields_names = displayable_field_names
.iter()
.take(3)
.map(|n| format!("`{}`", n))
.collect::<Vec<_>>()
.join(", ");
struct_span_err!(
tcx.sess,
self.tcx.sess,
span,
E0063,
"missing field{} {}{} in initializer of `{}`",
pluralize!(remaining_fields.len()),
pluralize!(len),
remaining_fields_names,
truncated_fields_error,
adt_ty