From de6f430140a49e3ecf34dcb914326bb5b9789772 Mon Sep 17 00:00:00 2001
From: Dawer <7803845+iDawer@users.noreply.github.com>
Date: Thu, 6 May 2021 13:15:40 +0500
Subject: Fix panics on pattern_arena.borrow with ugly cloning

---
 .../hir_ty/src/diagnostics/pattern/deconstruct_pat.rs | 19 +++++++++----------
 crates/hir_ty/src/diagnostics/pattern/usefulness.rs   | 12 ++++++------
 2 files changed, 15 insertions(+), 16 deletions(-)

(limited to 'crates/hir_ty')

diff --git a/crates/hir_ty/src/diagnostics/pattern/deconstruct_pat.rs b/crates/hir_ty/src/diagnostics/pattern/deconstruct_pat.rs
index 479e0dc73..ddf6b1198 100644
--- a/crates/hir_ty/src/diagnostics/pattern/deconstruct_pat.rs
+++ b/crates/hir_ty/src/diagnostics/pattern/deconstruct_pat.rs
@@ -837,20 +837,19 @@ impl Fields {
         pat: PatId,
         cx: &MatchCheckCtx<'_>,
     ) -> Self {
-        // TODO: these alocations are so unfortunate (+1 for switching to references)
-        match cx.pattern_arena.borrow()[pat].kind.as_ref() {
+        // TODO: these alocations and clones are so unfortunate (+1 for switching to references)
+        let mut arena = cx.pattern_arena.borrow_mut();
+        match arena[pat].kind.as_ref() {
             PatKind::Deref { subpattern } => {
                 assert_eq!(self.len(), 1);
-                let subpattern = cx.pattern_arena.borrow_mut().alloc(subpattern.clone());
-                Fields::from_single_pattern(subpattern)
+                let subpattern = subpattern.clone();
+                Fields::from_single_pattern(arena.alloc(subpattern))
             }
             PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => {
-                let subpatterns = subpatterns.iter().map(|field_pat| {
-                    (
-                        field_pat.field,
-                        cx.pattern_arena.borrow_mut().alloc(field_pat.pattern.clone()),
-                    )
-                });
+                let subpatterns = subpatterns.clone();
+                let subpatterns = subpatterns
+                    .iter()
+                    .map(|field_pat| (field_pat.field, arena.alloc(field_pat.pattern.clone())));
                 self.replace_with_fieldpats(subpatterns)
             }
 
diff --git a/crates/hir_ty/src/diagnostics/pattern/usefulness.rs b/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
index 28b9e71f8..3bfb7afed 100644
--- a/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
+++ b/crates/hir_ty/src/diagnostics/pattern/usefulness.rs
@@ -94,12 +94,12 @@ impl PatIdExt for PatId {
     fn expand_or_pat(self, cx: &MatchCheckCtx<'_>) -> Vec<Self> {
         fn expand(pat: PatId, vec: &mut Vec<PatId>, mut pat_arena: &mut PatternArena) {
             if let PatKind::Or { pats } = pat_arena[pat].kind.as_ref() {
-                // for pat in pats {
-                //     // TODO(iDawer): Ugh, I want to go back to references (PatId -> &Pat)
-                //     let pat = pat_arena.alloc(pat.clone());
-                //     expand(pat, vec, pat_arena);
-                // }
-                todo!()
+                let pats = pats.clone();
+                for pat in pats {
+                    // TODO(iDawer): Ugh, I want to go back to references (PatId -> &Pat)
+                    let pat = pat_arena.alloc(pat.clone());
+                    expand(pat, vec, pat_arena);
+                }
             } else {
                 vec.push(pat)
             }
-- 
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