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Improve error message for uninhabited patterns

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Ayaz Hafiz 2022-09-19 10:55:02 -05:00
parent 147636f42b
commit 0f0e414272
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4 changed files with 64 additions and 40 deletions
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33
crates/compiler/can/src/exhaustive.rs
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@ -3,15 +3,11 @@ use crate::pattern::DestructType;
use roc_collections::all::HumanIndex;
use roc_error_macros::internal_error;
use roc_exhaustive::{
is_useful, Ctor, CtorName, Error, Guard, Literal, Pattern, RedundantReason, RenderAs, TagId,
Union,
is_useful, Ctor, CtorName, Error, Guard, Literal, Pattern, RenderAs, TagId, Union,
};
use roc_module::ident::{TagIdIntType, TagName};
use roc_module::symbol::ModuleId;
use roc_region::all::{Loc, Region};
use roc_types::subs::{
Content, FlatType, GetSubsSlice, RedundantMark, Subs, SubsFmtContent, Variable,
};
use roc_types::subs::{Content, FlatType, RedundantMark, Subs, SubsFmtContent, Variable};
use roc_types::types::AliasKind;
pub use roc_exhaustive::Context as ExhaustiveContext;
@ -342,28 +338,31 @@ fn to_nonredundant_rows(subs: &Subs, rows: SketchedRows) -> NonRedundantSummary
.map(|pattern| pattern.reify(subs))
.collect();
let is_redundant = if !is_inhabited_row(&next_row) {
Some(RedundantReason::Uninhabited)
let redundant_err = if !is_inhabited_row(&next_row) {
Some(Error::Unmatchable {
overall_region,
branch_region: region,
index: HumanIndex::zero_based(row_number),
})
} else if !(matches!(guard, Guard::HasGuard)
|| is_useful(checked_rows.clone(), next_row.clone()))
{
Some(RedundantReason::PreviouslyCovered)
Some(Error::Redundant {
overall_region,
branch_region: region,
index: HumanIndex::zero_based(row_number),
})
} else {
None
};
match is_redundant {
match redundant_err {
None => {
checked_rows.push(next_row);
}
Some(reason) => {
Some(err) => {
redundancies.push(redundant_mark);
errors.push(Error::Redundant {
overall_region,
branch_region: region,
index: HumanIndex::zero_based(row_number),
reason,
});
errors.push(err);
}
}
}