Merge #701

701: Minor type inference tweaks r=flodiebold a=marcusklaas

Pass down expectation for reference expressions and type the guard in match expressions.

I wasn't able to add a test for the former addition because the type variable previously introduced would always resolve to the right type in the things I tried!

Co-authored-by: Marcus Klaas de Vries <mail@marcusklaas.nl>

crates/ra_hir/src/expr.rs

@@ -219,7 +219,7 @@ pub use ra_syntax::ast::BinOp as BinaryOp;
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct MatchArm {
     pub pats: Vec<PatId>,
-    // guard: Option<ExprId>, // TODO
+    pub guard: Option<ExprId>,
     pub expr: ExprId,
 }
 
@@ -515,10 +515,12 @@ impl ExprCollector {
                         MatchArm {
                             pats: vec![pat],
                             expr: then_branch,
+                            guard: None,
                         },
                         MatchArm {
                             pats: vec![placeholder_pat],
                             expr: else_branch,
+                            guard: None,
                         },
                     ];
                     self.alloc_expr(
@@ -617,6 +619,10 @@ 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()
+                                .and_then(|guard| guard.expr())
+                                .map(|e| self.collect_expr(e)),
                         })
                         .collect()
                 } else {

crates/ra_hir/src/ty.rs

@@ -1488,7 +1488,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     for &pat in &arm.pats {
                         let _pat_ty = self.infer_pat(pat, &input_ty);
                     }
-                    // TODO type the guard
+                    if let Some(guard_expr) = arm.guard {
+                        self.infer_expr(guard_expr, &Expectation::has_type(Ty::Bool));
+                    }
                     self.infer_expr(arm.expr, &expected);
                 }
 
@@ -1561,9 +1563,17 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 cast_ty
             }
             Expr::Ref { expr, mutability } => {
-                // TODO pass the expectation down
-                let inner_ty = self.infer_expr(*expr, &Expectation::none());
+                let expectation = if let Ty::Ref(ref subty, expected_mutability) = expected.ty {
+                    if expected_mutability == Mutability::Mut && *mutability == Mutability::Shared {
+                        // TODO: throw type error - expected mut reference but found shared ref,
+                        // which cannot be coerced
+                    }
+                    Expectation::has_type((**subty).clone())
+                } else {
+                    Expectation::none()
+                };
                 // TODO reference coercions etc.
+                let inner_ty = self.infer_expr(*expr, &expectation);
                 Ty::Ref(Arc::new(inner_ty), *mutability)
             }
             Expr::UnaryOp { expr, op } => {

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

@@ -1,10 +1,10 @@
 ---
-created: "2019-01-22T14:44:59.880187500+00:00"
-creator: insta@0.4.0
+created: "2019-01-28T21:58:55.559331849+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
 ---
-[68; 262) '{     ...  d; }': ()
+[68; 289) '{     ...  d; }': ()
 [78; 79) 'e': E
 [82; 95) 'E::A { x: 3 }': E
 [92; 93) '3': usize
@@ -15,15 +15,18 @@ source: "crates\\ra_hir\\src\\ty\\tests.rs"
 [129; 148) 'E::A {..._var }': E
 [139; 146) 'new_var': usize
 [151; 152) 'e': E
-[159; 218) 'match ...     }': usize
+[159; 245) 'match ...     }': usize
 [165; 166) 'e': E
 [177; 187) 'E::A { x }': E
 [184; 185) 'x': usize
 [191; 192) 'x': usize
 [202; 206) 'E::B': E
-[210; 211) '1': usize
-[229; 248) 'ref d ...{ .. }': &E
-[237; 248) 'E::A { .. }': E
-[251; 252) 'e': E
-[258; 259) 'd': &E
+[210; 213) 'foo': bool
+[217; 218) '1': usize
+[228; 232) 'E::B': E
+[236; 238) '10': usize
+[256; 275) 'ref d ...{ .. }': &E
+[264; 275) 'E::A { .. }': E
+[278; 279) 'e': E
+[285; 286) 'd': &E
 

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

@@ -371,6 +371,7 @@ fn test(x: &str, y: isize) {
 
     let b = [a, ["b"]];
     let x: [u8; 0] = [];
+    let z: &[u8] = &[1, 2, 3];
 }
 "#,
     );
@@ -426,7 +427,8 @@ fn test() {
 
     match e {
         E::A { x } => x,
-        E::B => 1,
+        E::B if foo => 1,
+        E::B => 10,
     };
 
     let ref d @ E::A { .. } = e;