Add test for passing on ref expectations

crates/ra_hir/src/expr.rs

@@ -615,10 +615,10 @@ impl ExprCollector {
                         .map(|arm| MatchArm {
                             pats: arm.pats().map(|p| self.collect_pat(p)).collect(),
                             expr: self.collect_expr_opt(arm.expr()),
-                            guard: arm.guard().map(|guard| {
-                                let e = guard.expr().expect("every guard should have an expr");
-                                self.collect_expr(e)
-                            }),
+                            guard: arm
+                                .guard()
+                                .and_then(|guard| guard.expr())
+                                .map(|e| self.collect_expr(e)),
                         })
                         .collect()
                 } else {

crates/ra_hir/src/ty/snapshots/tests__infer_array.snap

@@ -1,12 +1,12 @@
 ---
-created: "2019-01-22T14:44:59.880187500+00:00"
-creator: insta@0.4.0
+created: "2019-01-30T20:08:05.185312835+00:00"
+creator: insta@0.5.2
 expression: "&result"
-source: "crates\\ra_hir\\src\\ty\\tests.rs"
+source: crates/ra_hir/src/ty/tests.rs
 ---
 [9; 10) 'x': &str
 [18; 19) 'y': isize
-[28; 293) '{     ... []; }': ()
+[28; 324) '{     ... 3]; }': ()
 [38; 39) 'a': [&str]
 [42; 45) '[x]': [&str]
 [43; 44) 'x': &str
@@ -56,4 +56,10 @@ source: "crates\\ra_hir\\src\\ty\\tests.rs"
 [260; 263) '"b"': &str
 [275; 276) 'x': [u8]
 [288; 290) '[]': [u8]
+[300; 301) 'z': &[u8]
+[311; 321) '&[1, 2, 3]': &[u8]
+[312; 321) '[1, 2, 3]': [u8]
+[313; 314) '1': u8
+[316; 317) '2': u8
+[319; 320) '3': u8
 

crates/ra_hir/src/ty/tests.rs

@@ -366,6 +366,7 @@ fn test(x: &str, y: isize) {
 
     let b = [a, ["b"]];
     let x: [u8; 0] = [];
+    let z: &[u8] = &[1, 2, 3];
 }
 "#,
     );