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//! Contains checks that must be run to validate matches before performing usefulness analysis.
use crate::constructor::Constructor::*;
use crate::pat_column::PatternColumn;
use crate::{MatchArm, PatCx};
/// Validate that deref patterns and normal constructors aren't used to match on the same place.
pub(crate) fn detect_mixed_deref_pat_ctors<'p, Cx: PatCx>(
cx: &Cx,
arms: &[MatchArm<'p, Cx>],
) -> Result<(), Cx::Error> {
let pat_column = PatternColumn::new(arms);
detect_mixed_deref_pat_ctors_inner(cx, &pat_column)
}
fn detect_mixed_deref_pat_ctors_inner<'p, Cx: PatCx>(
cx: &Cx,
column: &PatternColumn<'p, Cx>,
) -> Result<(), Cx::Error> {
let Some(ty) = column.head_ty() else {
return Ok(());
};
// Check for a mix of deref patterns and normal constructors.
let mut deref_pat = None;
let mut normal_pat = None;
for pat in column.iter() {
match pat.ctor() {
// The analysis can handle mixing deref patterns with wildcards and opaque patterns.
Wildcard | Opaque(_) => {}
DerefPattern(_) => deref_pat = Some(pat),
// Nothing else can be compared to deref patterns in `Constructor::is_covered_by`.
_ => normal_pat = Some(pat),
}
}
if let Some(deref_pat) = deref_pat
&& let Some(normal_pat) = normal_pat
{
return Err(cx.report_mixed_deref_pat_ctors(deref_pat, normal_pat));
}
// Specialize and recurse into the patterns' fields.
let set = column.analyze_ctors(cx, &ty)?;
for ctor in set.present {
for specialized_column in column.specialize(cx, &ty, &ctor).iter() {
detect_mixed_deref_pat_ctors_inner(cx, specialized_column)?;
}
}
Ok(())
}
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