From 49e89772f63e10ebeb3c8720bd0b0ef8244f6c4a Mon Sep 17 00:00:00 2001
From: Jeremy Kolb <kjeremy@gmail.com>
Date: Sun, 27 Oct 2019 21:26:12 -0400
Subject: Preliminary enum variant support

---
 crates/ra_ide_api/src/call_info.rs                 | 32 ++++++++++++++++++-
 .../ra_ide_api/src/display/function_signature.rs   | 37 +++++++++++++++++++++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/crates/ra_ide_api/src/call_info.rs b/crates/ra_ide_api/src/call_info.rs
index 29ae2f552..e6bdaae6a 100644
--- a/crates/ra_ide_api/src/call_info.rs
+++ b/crates/ra_ide_api/src/call_info.rs
@@ -29,7 +29,7 @@ pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Option<Cal
                     (CallInfo::with_fn(db, it), it.data(db).has_self_param())
                 }
                 hir::CallableDef::Struct(it) => (CallInfo::with_struct(db, it), false),
-                hir::CallableDef::EnumVariant(_it) => return None,
+                hir::CallableDef::EnumVariant(it) => (CallInfo::with_enum_variant(db, it), false),
             }
         }
         FnCallNode::MethodCallExpr(expr) => {
@@ -129,6 +129,12 @@ impl CallInfo {
         CallInfo { signature, active_parameter: None }
     }
 
+    fn with_enum_variant(db: &RootDatabase, variant: hir::EnumVariant) -> Self {
+        let signature = FunctionSignature::from_enum_variant(db, variant);
+
+        CallInfo { signature, active_parameter: None }
+    }
+
     fn parameters(&self) -> &[String] {
         &self.signature.parameters
     }
@@ -485,4 +491,28 @@ fn main() {
         assert_eq!(info.doc().map(|it| it.into()), Some("A cool tuple struct".to_string()));
         assert_eq!(info.active_parameter, Some(1));
     }
+
+    #[test]
+    fn works_for_enum_variants() {
+        let info = call_info(
+            r#"
+enum E {
+    /// A Variant
+    A(i32),
+    /// Another
+    B,
+    /// And C
+    C(a: i32, b: i32)
+}
+
+fn main() {
+    let a = E::A(<|>);
+}
+            "#,
+        );
+
+        assert_eq!(info.label(), "E::A(0: i32)");
+        assert_eq!(info.doc().map(|it| it.into()), Some("A Variant".to_string()));
+        assert_eq!(info.active_parameter, Some(0));
+    }
 }
diff --git a/crates/ra_ide_api/src/display/function_signature.rs b/crates/ra_ide_api/src/display/function_signature.rs
index 6555f8619..6b169b3ae 100644
--- a/crates/ra_ide_api/src/display/function_signature.rs
+++ b/crates/ra_ide_api/src/display/function_signature.rs
@@ -16,6 +16,7 @@ use crate::{
 pub enum SigKind {
     Function,
     Struct,
+    EnumVariant,
 }
 
 /// Contains information about a function signature
@@ -70,13 +71,46 @@ impl FunctionSignature {
             visibility: node.visibility().map(|n| n.syntax().text().to_string()),
             name: node.name().map(|n| n.text().to_string()),
             ret_type: node.name().map(|n| n.text().to_string()),
-            parameters: /*param_list(node)*/ params,
+            parameters: params,
             generic_parameters: generic_parameters(&node),
             where_predicates: where_predicates(&node),
             doc: None,
         }
         .with_doc_opt(doc)
     }
+
+    pub(crate) fn from_enum_variant(db: &db::RootDatabase, variant: hir::EnumVariant) -> Self {
+        let doc = variant.docs(db);
+
+        let parent_name = match variant.parent_enum(db).name(db) {
+            Some(name) => name.to_string(),
+            None => "missing".into(),
+        };
+
+        let name = format!("{}::{}", parent_name, variant.name(db).unwrap());
+
+        let params = variant
+            .fields(db)
+            .into_iter()
+            .map(|field: hir::StructField| {
+                let name = field.name(db);
+                let ty = field.ty(db);
+                format!("{}: {}", name, ty.display(db))
+            })
+            .collect();
+
+        FunctionSignature {
+            kind: SigKind::EnumVariant,
+            visibility: None,
+            name: Some(name),
+            ret_type: None,
+            parameters: params,
+            generic_parameters: vec![],
+            where_predicates: vec![],
+            doc: None,
+        }
+        .with_doc_opt(doc)
+    }
 }
 
 impl From<&'_ ast::FnDef> for FunctionSignature {
@@ -120,6 +154,7 @@ impl Display for FunctionSignature {
             match self.kind {
                 SigKind::Function => write!(f, "fn {}", name)?,
                 SigKind::Struct => write!(f, "struct {}", name)?,
+                SigKind::EnumVariant => write!(f, "{}", name)?,
             }
         }
 
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