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fix false positive for enum with no variants

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This commit is contained in:
Josh Mcguigan 2020-04-14 16:06:57 -07:00
parent c82e7696e6
commit 360bdf653b
3 changed files with 51 additions and 3 deletions
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42
crates/ra_hir_ty/src/_match.rs
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@ -194,9 +194,10 @@ use smallvec::{smallvec, SmallVec};
use crate::{
db::HirDatabase,
expr::{Body, Expr, Literal, Pat, PatId},
InferenceResult,
ApplicationTy, InferenceResult, Ty, TypeCtor,
};
use hir_def::{adt::VariantData, EnumVariantId, VariantId};
use hir_def::{adt::VariantData, AdtId, EnumVariantId, VariantId};
use ra_arena::Idx;
#[derive(Debug, Clone, Copy)]
/// Either a pattern from the source code being analyzed, represented as
@ -512,6 +513,7 @@ pub enum Usefulness {
}
pub struct MatchCheckCtx<'a> {
pub match_expr: Idx<Expr>,
pub body: Arc<Body>,
pub infer: Arc<InferenceResult>,
pub db: &'a dyn HirDatabase,
@ -530,6 +532,16 @@ pub(crate) fn is_useful(
matrix: &Matrix,
v: &PatStack,
) -> MatchCheckResult<Usefulness> {
// Handle the special case of enums with no variants. In that case, no match
// arm is useful.
if let Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(AdtId::EnumId(enum_id)), .. }) =
cx.infer[cx.match_expr].strip_references()
{
if cx.db.enum_data(*enum_id).variants.is_empty() {
return Ok(Usefulness::NotUseful);
}
}
if v.is_empty() {
let result = if matrix.is_empty() { Usefulness::Useful } else { Usefulness::NotUseful };
@ -1618,6 +1630,32 @@ mod tests {
check_no_diagnostic(content);
}
#[test]
fn enum_never() {
let content = r"
enum Never {}
fn test_fn(never: Never) {
match never {}
}
";
check_no_diagnostic(content);
}
#[test]
fn enum_never_ref() {
let content = r"
enum Never {}
fn test_fn(never: &Never) {
match never {}
}
";
check_no_diagnostic(content);
}
}
#[cfg(test)]