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Add comments to obscure code, remove unnesecary parameter from closure

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This commit is contained in:
Bryysen 2022-08-07 22:28:16 +02:00
parent 4ee2fe308b
commit 399796d2b3
1 changed files with 18 additions and 6 deletions
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24
compiler/rustc_typeck/src/check/check.rs
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@ -1499,16 +1499,18 @@ fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, vs: &'tcx [hir::Variant<'tcx>], def_id: L
check_transparent(tcx, sp, def);
}
/// Part of enum check, errors if two or more discriminants are equal
fn detect_discriminant_duplicate<'tcx>(
tcx: TyCtxt<'tcx>,
mut discrs: Vec<(VariantIdx, Discr<'tcx>)>,
vs: &'tcx [hir::Variant<'tcx>],
self_span: Span,
) {
let report = |var: &hir::Variant<'_>,
dis: Discr<'tcx>,
// Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate
let report = |dis: Discr<'tcx>,
idx: usize,
err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>| {
let var = &vs[idx];
let (span, display_discr) = match var.disr_expr {
Some(ref expr) => {
// In the case the discriminant is both a duplicate and overflowed, let the user know
@ -1517,11 +1519,16 @@ fn detect_discriminant_duplicate<'tcx>(
&& *lit_value != dis.val
{
(tcx.hir().span(expr.hir_id), format!("`{dis}` (overflowed from `{lit_value}`)"))
// Otherwise, format the value as-is
} else {
(tcx.hir().span(expr.hir_id), format!("`{dis}`"))
}
}
None => {
// At this point we know this discriminant is a duplicate, and was not explicitly
// assigned by the user. Here we iterate backwards to fetch the hir for the last
// explictly assigned discriminant, and letting the user know that this was the
// increment startpoint, and how many steps from there leading to the duplicate
if let Some((n, hir::Variant { span, ident, .. })) =
vs[..idx].iter().rev().enumerate().find(|v| v.1.disr_expr.is_some())
{
@ -1542,16 +1549,20 @@ fn detect_discriminant_duplicate<'tcx>(
err.span_label(span, format!("{display_discr} assigned here"));
};
// Here we are looping through the discriminant vec, comparing each discriminant to oneanother.
// When a duplicate is detected, we instatiate an error and add a spanned note pointing to both
// initial and duplicate value. The duplicate discriminant is then discarded from the vec by swapping
// it with the last element and decrementing the vec.len by 1 (which is why we have to evaluate
// `discrs.len()` anew every iteration, and why this could be tricky to do in a functional style as
// we are mutating `discrs` on the fly).
let mut i = 0;
while i < discrs.len() {
let hir_var_i_idx = discrs[i].0.index();
let hir_var_i = &vs[hir_var_i_idx];
let mut error: Option<DiagnosticBuilder<'_, _>> = None;
let mut o = i + 1;
while o < discrs.len() {
let hir_var_o_idx = discrs[o].0.index();
let hir_var_o = &vs[hir_var_o_idx];
if discrs[i].1.val == discrs[o].1.val {
let err = error.get_or_insert_with(|| {
@ -1563,13 +1574,14 @@ fn detect_discriminant_duplicate<'tcx>(
discrs[i].1,
);
report(hir_var_i, discrs[i].1, hir_var_i_idx, &mut ret);
report(discrs[i].1, hir_var_i_idx, &mut ret);
ret
});
report(hir_var_o, discrs[o].1, hir_var_o_idx, err);
report(discrs[o].1, hir_var_o_idx, err);
// Safe to unwrap here, as we wouldn't reach this point if `discrs` was empty
discrs[o] = *discrs.last().unwrap();
discrs.pop();
} else {