Added const bodies and static body to the ast

and added inference the inference test

reduce code duplication

crates/ra_syntax/src/ast/generated.rs

@@ -629,7 +629,11 @@ impl ast::TypeParamsOwner for ConstDef {}
 impl ast::AttrsOwner for ConstDef {}
 impl ast::DocCommentsOwner for ConstDef {}
 impl ast::TypeAscriptionOwner for ConstDef {}
-impl ConstDef {}
+impl ConstDef {
+    pub fn body(&self) -> Option<&Expr> {
+        super::child_opt(self)
+    }
+}
 
 // ContinueExpr
 #[derive(Debug, PartialEq, Eq, Hash)]
@@ -657,7 +661,6 @@ impl ToOwned for ContinueExpr {
 }
 
 
-
 impl ContinueExpr {}
 
 // DynTraitType
@@ -3808,7 +3811,11 @@ impl ast::TypeParamsOwner for StaticDef {}
 impl ast::AttrsOwner for StaticDef {}
 impl ast::DocCommentsOwner for StaticDef {}
 impl ast::TypeAscriptionOwner for StaticDef {}
-impl StaticDef {}
+impl StaticDef {
+    pub fn body(&self) -> Option<&Expr> {
+        super::child_opt(self)
+    }
+}
 
 // Stmt
 #[derive(Debug, PartialEq, Eq, Hash)]

crates/ra_syntax/src/grammar.ron

@@ -313,7 +313,7 @@ Grammar(
                 "DocCommentsOwner",
                 "TypeAscriptionOwner",
             ],
-            options: ["body","Block"],
+            options: [ ["body","Expr"]],
         ),
         "StaticDef": (
             traits: [
@@ -324,7 +324,7 @@ Grammar(
                 "DocCommentsOwner",
                 "TypeAscriptionOwner",
             ],
-            options: ["body","Block"],
+            options: [ ["body","Expr"]],
         ),
         "TypeAliasDef": (
             traits: [