Merge #1103

1103: Array inference r=flodiebold a=Lapz

Fixes the final item in #394. The only problem is that infering the repeat cause some types to be infered twices.
i.e 
```rust
fn test() {
    let y = unknown;
    [y, &y];
}
```

results in the following diff:

```diff
[11; 48) '{     ...&y]; }': ()
[21; 22) 'y': &{unknown}
[25; 32) 'unknown': &{unknown}
-[38; 45) '[y, &y]': [&&{unknown}]
+[38; 45) '[y, &y]': [&&{unknown};usize]
[39; 40) 'y': &{unknown}
+[39; 40) 'y': &{unknown}
[42; 44) '&y': &&{unknown}
[43; 44) 'y': &{unknown}
```

Should the code produce two inference results for 'y' and if not could any tell me what needs to change.

Co-authored-by: Lenard Pratt <[email protected]>

2 files changed, 24 insertions, 2 deletions

diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index a06a6375d..c2ab19d97 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -17,8 +17,8 @@ pub use self::{
     generated::*,
     traits::*,
     tokens::*,
-    extensions::{PathSegmentKind, StructKind, FieldKind, SelfParamKind},
-    expr_extensions::{ElseBranch, PrefixOp, BinOp, LiteralKind},
+    extensions::{PathSegmentKind, StructKind,FieldKind, SelfParamKind},
+    expr_extensions::{ElseBranch, PrefixOp, BinOp, LiteralKind,ArrayExprKind},
 };
 
 /// The main trait to go from untyped `SyntaxNode`  to a typed ast. The
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
index 1d8313810..9484c3b9b 100644
--- a/crates/ra_syntax/src/ast/expr_extensions.rs
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -193,6 +193,28 @@ impl ast::BinExpr {
     }
 }
 
+pub enum ArrayExprKind<'a> {
+    Repeat { initializer: Option<&'a ast::Expr>, repeat: Option<&'a ast::Expr> },
+    ElementList(AstChildren<'a, ast::Expr>),
+}
+
+impl ast::ArrayExpr {
+    pub fn kind(&self) -> ArrayExprKind {
+        if self.is_repeat() {
+            ArrayExprKind::Repeat {
+                initializer: children(self).nth(0),
+                repeat: children(self).nth(1),
+            }
+        } else {
+            ArrayExprKind::ElementList(children(self))
+        }
+    }
+
+    fn is_repeat(&self) -> bool {
+        self.syntax().children_with_tokens().any(|it| it.kind() == SEMI)
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum LiteralKind {
     String,