Merge #3169

3169: Show record field names in Enum completion r=flodiebold a=adamrk

Adresses https://github.com/rust-analyzer/rust-analyzer/issues/2947.
Previously the details shown when autocompleting an Enum variant would look like the variant was a tuple even if it was a record:
![2020-02-16-15:59:32_crop](https://user-images.githubusercontent.com/16367467/74607233-64f21980-50d7-11ea-99db-e973e29c71d7.png)

This change will show the names of the fields for a record and use curly braces instead of parentheses:
![2020-02-16-15:33:00_crop](https://user-images.githubusercontent.com/16367467/74607251-8ce17d00-50d7-11ea-9d4d-38d198a4aec0.png)

This required exposing the type `adt::StructKind` from `ra_hir` and adding a function 
```
kind(self, db: &impl HirDatabase) -> StructKind
```
in the `impl` of `EnumVariant`. 

There was also a previously existing function `is_unit(self, db: &impl HirDatabase) -> bool` for `EnumVariant` which I removed because it seemed redundant after adding `kind`.

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

1 files changed, 5 insertions, 4 deletions

diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index 6a2aded02..c2a3703fa 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -9,6 +9,7 @@ use std::iter;
 use std::sync::Arc;
 
 use hir_def::{
+    adt::StructKind,
     builtin_type::BuiltinType,
     generics::{TypeParamProvenance, WherePredicate, WherePredicateTarget},
     path::{GenericArg, Path, PathSegment, PathSegments},
@@ -805,8 +806,8 @@ fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> PolyFn
 /// Build the type of a tuple struct constructor.
 fn type_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> Binders<Ty> {
     let struct_data = db.struct_data(def.into());
-    if struct_data.variant_data.is_unit() {
-        return type_for_adt(db, def.into()); // Unit struct
+    if let StructKind::Unit = struct_data.variant_data.kind() {
+        return type_for_adt(db, def.into());
     }
     let generics = generics(db, def.into());
     let substs = Substs::bound_vars(&generics);
@@ -830,8 +831,8 @@ fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId
 fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId) -> Binders<Ty> {
     let enum_data = db.enum_data(def.parent);
     let var_data = &enum_data.variants[def.local_id].variant_data;
-    if var_data.is_unit() {
-        return type_for_adt(db, def.parent.into()); // Unit variant
+    if let StructKind::Unit = var_data.kind() {
+        return type_for_adt(db, def.parent.into());
     }
     let generics = generics(db, def.parent.into());
     let substs = Substs::bound_vars(&generics);