1 files changed, 87 insertions, 0 deletions

diff --git a/crates/ra_ide_api/src/completion/complete_pattern.rs b/crates/ra_ide_api/src/completion/complete_pattern.rs
new file mode 100644
index 000000000..3cf79c080
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_pattern.rs
@@ -0,0 +1,87 @@
+use crate::completion::{CompletionContext, Completions};
+
+/// Completes constats and paths in patterns.
+pub(super) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
+    if !ctx.is_pat_binding {
+        return;
+    }
+    // TODO: ideally, we should look at the type we are matching against and
+    // suggest variants + auto-imports
+    let names = ctx.resolver.all_names(ctx.db);
+    for (name, res) in names.into_iter() {
+        let r = res.as_ref();
+        let def = match r.take_types().or(r.take_values()) {
+            Some(hir::Resolution::Def(def)) => def,
+            _ => continue,
+        };
+        match def {
+            hir::ModuleDef::Enum(..)
+            | hir::ModuleDef::EnumVariant(..)
+            | hir::ModuleDef::Const(..)
+            | hir::ModuleDef::Module(..) => (),
+            _ => continue,
+        }
+        acc.add_resolution(ctx, name.to_string(), &res)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use insta::assert_debug_snapshot_matches;
+    use crate::completion::{CompletionItem, CompletionKind, do_completion};
+
+    fn complete(code: &str) -> Vec<CompletionItem> {
+        do_completion(code, CompletionKind::Reference)
+    }
+
+    #[test]
+    fn completes_enum_variants_and_modules() {
+        let completions = complete(
+            r"
+            enum E { X }
+            use self::E::X;
+            const Z: E = E::X;
+            mod m {}
+
+            static FOO: E = E::X;
+            struct Bar { f: u32 }
+
+            fn foo() {
+               match E::X {
+                   <|>
+               }
+            }
+            ",
+        );
+        assert_debug_snapshot_matches!(completions, @r###"[
+    CompletionItem {
+        label: "E",
+        source_range: [246; 246),
+        delete: [246; 246),
+        insert: "E",
+        kind: Enum
+    },
+    CompletionItem {
+        label: "X",
+        source_range: [246; 246),
+        delete: [246; 246),
+        insert: "X",
+        kind: EnumVariant
+    },
+    CompletionItem {
+        label: "Z",
+        source_range: [246; 246),
+        delete: [246; 246),
+        insert: "Z",
+        kind: Const
+    },
+    CompletionItem {
+        label: "m",
+        source_range: [246; 246),
+        delete: [246; 246),
+        insert: "m",
+        kind: Module
+    }
+]"###);
+    }
+}