From 8cb139090f969c9e8f8eecf9ffe3cd89624526d5 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Tue, 28 Apr 2020 22:45:46 +0200
Subject: [PATCH] Complete union fields after dot

---
 crates/ra_hir/src/code_model.rs              | 27 +++++++-------
 crates/ra_ide/src/completion/complete_dot.rs | 38 ++++++++++++++++++++
 2 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index fb788736d8..3fb4195718 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -1157,18 +1157,21 @@ impl Type {
 
     pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
         if let Ty::Apply(a_ty) = &self.ty.value {
-            if let TypeCtor::Adt(AdtId::StructId(s)) = a_ty.ctor {
-                let var_def = s.into();
-                return db
-                    .field_types(var_def)
-                    .iter()
-                    .map(|(local_id, ty)| {
-                        let def = Field { parent: var_def.into(), id: local_id };
-                        let ty = ty.clone().subst(&a_ty.parameters);
-                        (def, self.derived(ty))
-                    })
-                    .collect();
-            }
+            let variant_id = match a_ty.ctor {
+                TypeCtor::Adt(AdtId::StructId(s)) => s.into(),
+                TypeCtor::Adt(AdtId::UnionId(u)) => u.into(),
+                _ => return Vec::new(),
+            };
+
+            return db
+                .field_types(variant_id)
+                .iter()
+                .map(|(local_id, ty)| {
+                    let def = Field { parent: variant_id.into(), id: local_id };
+                    let ty = ty.clone().subst(&a_ty.parameters);
+                    (def, self.derived(ty))
+                })
+                .collect();
         };
         Vec::new()
     }
diff --git a/crates/ra_ide/src/completion/complete_dot.rs b/crates/ra_ide/src/completion/complete_dot.rs
index 814354ffa6..05f825c6fe 100644
--- a/crates/ra_ide/src/completion/complete_dot.rs
+++ b/crates/ra_ide/src/completion/complete_dot.rs
@@ -249,6 +249,44 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_union_field_completion() {
+        assert_debug_snapshot!(
+            do_ref_completion(
+                r"
+            union Un {
+                field: u8,
+                other: u16,
+            }
+
+            fn foo(u: Un) {
+                u.<|>
+            }
+            ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "field",
+                source_range: 140..140,
+                delete: 140..140,
+                insert: "field",
+                kind: Field,
+                detail: "u8",
+            },
+            CompletionItem {
+                label: "other",
+                source_range: 140..140,
+                delete: 140..140,
+                insert: "other",
+                kind: Field,
+                detail: "u16",
+            },
+        ]
+        "###
+        );
+    }
+
     #[test]
     fn test_method_completion() {
         assert_debug_snapshot!(