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Suggest array indexing when tuple indexing on an array #54292

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Sep 21, 2018
Merged

Suggest array indexing when tuple indexing on an array #54292

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30556d5
Suggest array indexing when tuple indexing on an array.
memoryruins Sep 17, 2018
dff1bc1
Set diagnostic applicability based on array length
memoryruins Sep 18, 2018
73fdc81
Use expr's span
memoryruins Sep 18, 2018
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6 changes: 6 additions & 0 deletions src/librustc_typeck/check/mod.rs
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Expand Up @@ -3344,6 +3344,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
}
};
}
ty::Array(ty, _) if ty.is_numeric() => {
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I wonder if you can get the numeric value of field and check wether it is smaller than ty::Array(_, len). That would give us a great degree of confidence that the suggestion is correct, we could even switch between Applicability levels given that... 🤔

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Is there any reason to limit this suggestion to only [{integer}; _] and [{float}; _]? I'm not against it, as being conservative in suggestions is not bad, I just want to hear what was your reasoning.

let base = self.tcx.hir.node_to_pretty_string(base.id);
let msg = format!("attempting to use tuple indexing on an array; try");
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Let's change the wording to something along the lines of instead of using tuple indexing use array indexing.

let suggestion = format!("{}[{}]", base, field);
err.span_suggestion(field.span, &msg, suggestion);
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Please use span_suggestion_with_applicability and Applicability::MaybeIncorrect.

},
ty::RawPtr(..) => {
let base = self.tcx.hir.node_to_pretty_string(base.id);
let msg = format!("`{}` is a native pointer; try dereferencing it", base);
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9 changes: 9 additions & 0 deletions src/test/ui/issues/issue-53712.rs
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@@ -0,0 +1,9 @@
// issue #53712: make the error generated by using tuple indexing on an array more specific

fn main() {
let arr = [10, 20, 30, 40, 50];
arr.0;
//~^ ERROR no field `0` on type `[{integer}; 5]` [E0609]
//~| HELP attempting to use tuple indexing on an array; try
//~| SUGGESTION arr[0]
}
9 changes: 9 additions & 0 deletions src/test/ui/issues/issue-53712.stderr
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@@ -0,0 +1,9 @@
error[E0609]: no field `0` on type `[{integer}; 5]`
--> $DIR/issue-53712.rs:5:9
|
LL | arr.0;
| ^ help: attempting to use tuple indexing on an array; try: `arr[0]`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0609`.