Merge #1815

1815: Support correct `$crate` expansion in macros r=uHOOCCOOHu a=uHOOCCOOHu

This PR makes normal use cases of `$crate` from macros work as expected.

It makes more macros from `std` work. Type inference works well with `panic`, `unimplemented`, `format`, and maybe more.
Sadly that `vec![1, 2, 3]` still not works, but it is not longer an issue about macro.

Screenshot:
![Screenshot_20190927_022136](https://user-images.githubusercontent.com/14816024/65714465-b4568f80-e0cd-11e9-8043-dd44c2ae8040.png)




Co-authored-by: uHOOCCOOHu <[email protected]>

1 files changed, 4 insertions, 5 deletions

diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 8e07fc186..2e4a489a0 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -609,7 +609,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         for (i, &subpat) in subpats.iter().enumerate() {
             let expected_ty = def
-                .and_then(|d| d.field(self.db, &Name::tuple_field_name(i)))
+                .and_then(|d| d.field(self.db, &Name::new_tuple_field(i)))
                 .map_or(Ty::Unknown, |field| field.ty(self.db))
                 .subst(&substs);
             let expected_ty = self.normalize_associated_types_in(expected_ty);
@@ -1374,10 +1374,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 )
                 .find_map(|derefed_ty| match canonicalized.decanonicalize_ty(derefed_ty.value) {
                     Ty::Apply(a_ty) => match a_ty.ctor {
-                        TypeCtor::Tuple { .. } => {
-                            let i = name.to_string().parse::<usize>().ok();
-                            i.and_then(|i| a_ty.parameters.0.get(i).cloned())
-                        }
+                        TypeCtor::Tuple { .. } => name
+                            .as_tuple_index()
+                            .and_then(|idx| a_ty.parameters.0.get(idx).cloned()),
                         TypeCtor::Adt(Adt::Struct(s)) => s.field(self.db, name).map(|field| {
                             self.write_field_resolution(tgt_expr, field);
                             field.ty(self.db).subst(&a_ty.parameters)