Implement reference / pointer types

- parse them
 - infer types of & and * expressions

crates/ra_syntax/src/ast.rs

@@ -394,3 +394,42 @@ impl<'a> EnumVariant<'a> {
         StructFlavor::from_node(self)
     }
 }
+
+impl<'a> PointerType<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl<'a> ReferenceType<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl<'a> RefExpr<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum PrefixOp {
+    /// The `*` operator for dereferencing
+    Deref,
+    /// The `!` operator for logical inversion
+    Not,
+    /// The `-` operator for negation
+    Neg,
+}
+
+impl<'a> PrefixExpr<'a> {
+    pub fn op(&self) -> Option<PrefixOp> {
+        match self.syntax().first_child()?.kind() {
+            STAR => Some(PrefixOp::Deref),
+            EXCL => Some(PrefixOp::Not),
+            MINUS => Some(PrefixOp::Neg),
+            _ => None,
+        }
+    }
+}