Merge #475

475: Show types of fields in completion r=matklad a=matklad

![image](https://user-images.githubusercontent.com/1711539/50910524-0f146200-143f-11e9-84d6-0ba80761cd89.png)

r? @flodiebold 


Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

crates/ra_ide_api/src/completion/complete_dot.rs

@@ -28,13 +28,13 @@ fn complete_fields(acc: &mut Completions, ctx: &CompletionContext, receiver: Ty)
             Ty::Adt { def_id, .. } => {
                 match def_id.resolve(ctx.db)? {
                     Def::Struct(s) => {
-                        let variant_data = s.variant_data(ctx.db)?;
-                        for field in variant_data.fields() {
+                        for field in s.fields(ctx.db)? {
                             CompletionItem::new(
                                 CompletionKind::Reference,
                                 field.name().to_string(),
                             )
                             .kind(CompletionItemKind::Field)
+                            .set_detail(field.ty(ctx.db)?.map(|ty| ty.to_string()))
                             .add_to(acc);
                         }
                     }
@@ -72,7 +72,7 @@ mod tests {
                a.<|>
             }
             ",
-            r#"the_field"#,
+            r#"the_field "u32""#,
         );
     }
 
@@ -80,14 +80,14 @@ mod tests {
     fn test_struct_field_completion_self() {
         check_ref_completion(
             r"
-            struct A { the_field: u32 }
+            struct A { the_field: (u32,) }
             impl A {
                 fn foo(self) {
                     self.<|>
                 }
             }
             ",
-            r#"the_field"#,
+            r#"the_field "(u32,)""#,
         );
     }
 
@@ -95,14 +95,14 @@ mod tests {
     fn test_struct_field_completion_autoderef() {
         check_ref_completion(
             r"
-            struct A { the_field: u32 }
+            struct A { the_field: (u32, i32) }
             impl A {
                 fn foo(&self) {
                     self.<|>
                 }
             }
             ",
-            r#"the_field"#,
+            r#"the_field "(u32, i32)""#,
         );
     }
 

crates/ra_ide_api/src/completion/completion_item.rs

@@ -11,6 +11,7 @@ pub struct CompletionItem {
     /// completion.
     completion_kind: CompletionKind,
     label: String,
+    detail: Option<String>,
     lookup: Option<String>,
     snippet: Option<String>,
     kind: Option<CompletionItemKind>,
@@ -51,6 +52,7 @@ impl CompletionItem {
         Builder {
             completion_kind,
             label,
+            detail: None,
             lookup: None,
             snippet: None,
             kind: None,
@@ -60,6 +62,10 @@ impl CompletionItem {
     pub fn label(&self) -> &str {
         &self.label
     }
+    /// Short one-line additional information, like a type
+    pub fn detail(&self) -> Option<&str> {
+        self.detail.as_ref().map(|it| it.as_str())
+    }
     /// What string is used for filtering.
     pub fn lookup(&self) -> &str {
         self.lookup
@@ -87,6 +93,7 @@ impl CompletionItem {
 pub(crate) struct Builder {
     completion_kind: CompletionKind,
     label: String,
+    detail: Option<String>,
     lookup: Option<String>,
     snippet: Option<String>,
     kind: Option<CompletionItemKind>,
@@ -100,6 +107,7 @@ impl Builder {
     pub(crate) fn build(self) -> CompletionItem {
         CompletionItem {
             label: self.label,
+            detail: self.detail,
             lookup: self.lookup,
             snippet: self.snippet,
             kind: self.kind,
@@ -118,6 +126,14 @@ impl Builder {
         self.kind = Some(kind);
         self
     }
+    #[allow(unused)]
+    pub(crate) fn detail(self, detail: impl Into<String>) -> Builder {
+        self.set_detail(Some(detail))
+    }
+    pub(crate) fn set_detail(mut self, detail: Option<impl Into<String>>) -> Builder {
+        self.detail = detail.map(Into::into);
+        self
+    }
     pub(super) fn from_resolution(
         mut self,
         ctx: &CompletionContext,
@@ -227,6 +243,9 @@ impl Completions {
                 } else {
                     res.push_str(&c.label);
                 }
+                if let Some(detail) = &c.detail {
+                    res.push_str(&format!(" {:?}", detail));
+                }
                 if let Some(snippet) = &c.snippet {
                     res.push_str(&format!(" {:?}", snippet));
                 }