From d0e282f6b1a8c698212f7f76de2ff122e36e17a2 Mon Sep 17 00:00:00 2001
From: Josh Mcguigan <joshmcg88@gmail.com>
Date: Sun, 1 Mar 2020 07:08:05 -0800
Subject: handle arbitrary length slices

---
 crates/ra_hir_ty/src/infer/pat.rs      |  8 +++++---
 crates/ra_hir_ty/src/tests/patterns.rs | 33 ++++++++++++++++++++++++---------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/crates/ra_hir_ty/src/infer/pat.rs b/crates/ra_hir_ty/src/infer/pat.rs
index b991720ff..3fe1a4abb 100644
--- a/crates/ra_hir_ty/src/infer/pat.rs
+++ b/crates/ra_hir_ty/src/infer/pat.rs
@@ -188,10 +188,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Pat::Slice { prefix, slice, suffix } => {
                 if let Ty::Apply(ApplicationTy { ctor: TypeCtor::Slice, parameters }) = expected {
                     match (prefix.as_slice(), slice, suffix.as_slice()) {
-                        ([prefix_pat_id], None, []) => {
-                            let ty = self.infer_pat(*prefix_pat_id, &parameters.0[0], default_bm);
+                        (prefix_pat_ids, None, []) => {
+                            for pat_id in prefix_pat_ids {
+                                self.infer_pat(*pat_id, parameters.as_single(), default_bm);
+                            }
 
-                            Ty::apply_one(TypeCtor::Slice, ty)
+                            Ty::apply_one(TypeCtor::Slice, parameters.as_single().clone())
                         },
                         _ => Ty::Unknown,
                     }
diff --git a/crates/ra_hir_ty/src/tests/patterns.rs b/crates/ra_hir_ty/src/tests/patterns.rs
index fdc9dd180..6a9413521 100644
--- a/crates/ra_hir_ty/src/tests/patterns.rs
+++ b/crates/ra_hir_ty/src/tests/patterns.rs
@@ -143,28 +143,43 @@ fn infer_pattern_match_slice() {
 fn test() {
     let slice: &[f64] = &[0.0];
     match slice {
+        &[] => {},
         &[a] => {
             a;
+        },
+        &[b, c] => {
+            b;
+            c;
         }
         _ => {}
     }
 }
 "#),
     @r###"
-    [11; 129) '{     ...   } }': ()
+    [11; 210) '{     ...   } }': ()
     [21; 26) 'slice': &[f64]
     [37; 43) '&[0.0]': &[f64; _]
     [38; 43) '[0.0]': [f64; _]
     [39; 42) '0.0': f64
-    [49; 127) 'match ...     }': ()
+    [49; 208) 'match ...     }': ()
     [55; 60) 'slice': &[f64]
-    [71; 75) '&[a]': &[f64]
-    [72; 75) '[a]': [f64]
-    [73; 74) 'a': f64
-    [79; 105) '{     ...     }': ()
-    [93; 94) 'a': f64
-    [114; 115) '_': &[f64]
-    [119; 121) '{}': ()
+    [71; 74) '&[]': &[f64]
+    [72; 74) '[]': [f64]
+    [78; 80) '{}': ()
+    [90; 94) '&[a]': &[f64]
+    [91; 94) '[a]': [f64]
+    [92; 93) 'a': f64
+    [98; 124) '{     ...     }': ()
+    [112; 113) 'a': f64
+    [134; 141) '&[b, c]': &[f64]
+    [135; 141) '[b, c]': [f64]
+    [136; 137) 'b': f64
+    [139; 140) 'c': f64
+    [145; 186) '{     ...     }': ()
+    [159; 160) 'b': f64
+    [174; 175) 'c': f64
+    [195; 196) '_': &[f64]
+    [200; 202) '{}': ()
     "###
     );
 }
-- 
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