show local variable types in completion

crates/ra_hir/src/source_binder.rs

@@ -256,6 +256,14 @@ impl SourceAnalyzer {
         Some(self.infer.as_ref()?[pat_id].clone())
     }
 
+    pub fn type_of_pat_by_id(
+        &self,
+        _db: &impl HirDatabase,
+        pat_id: expr::PatId,
+    ) -> Option<crate::Ty> {
+        Some(self.infer.as_ref()?[pat_id].clone())
+    }
+
     pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
         let expr_id = self.body_source_map.as_ref()?.node_expr(&call.clone().into())?;
         self.infer.as_ref()?.method_resolution(expr_id)

crates/ra_ide_api/src/completion/presentation.rs

@@ -1,5 +1,5 @@
 //! This modules takes care of rendering various defenitions as completion items.
-use hir::{Docs, HasSource, HirDisplay, PerNs, Resolution};
+use hir::{Docs, HasSource, HirDisplay, PerNs, Resolution, Ty};
 use join_to_string::join;
 use ra_syntax::ast::NameOwner;
 use test_utils::tested_by;
@@ -80,10 +80,18 @@ impl Completions {
                 None,
             ),
         };
-        CompletionItem::new(completion_kind, ctx.source_range(), local_name)
+
-            .kind(kind)
+        let mut completion_item =
-            .set_documentation(docs)
+            CompletionItem::new(completion_kind, ctx.source_range(), local_name);
-            .add_to(self)
+        if let Resolution::LocalBinding(pat_id) = def {
+            let ty = ctx
+                .analyzer
+                .type_of_pat_by_id(ctx.db, pat_id.clone())
+                .filter(|t| t != &Ty::Unknown)
+                .map(|t| t.display(ctx.db).to_string());
+            completion_item = completion_item.set_detail(ty);
+        };
+        completion_item.kind(kind).set_documentation(docs).add_to(self)
     }
 
     pub(crate) fn add_function(&mut self, ctx: &CompletionContext, func: hir::Function) {

crates/ra_ide_api/src/completion/snapshots/completion_item__bindings_from_if_let.snap

@@ -1,5 +1,5 @@
 ---
-created: "2019-05-23T22:23:35.122168608Z"
+created: "2019-07-23T16:11:48.828805910Z"
 creator: insta@0.8.1
 source: crates/ra_ide_api/src/completion/completion_item.rs
 expression: kind_completions
@@ -18,6 +18,7 @@ expression: kind_completions
         delete: [214; 214),
         insert: "b",
         kind: Binding,
+        detail: "i32",
     },
     CompletionItem {
         label: "quux",

crates/ra_ide_api/src/completion/snapshots/completion_item__bindings_from_let.snap

@@ -1,5 +1,5 @@
 ---
-created: "2019-05-23T22:23:35.122797188Z"
+created: "2019-07-23T16:11:48.828811567Z"
 creator: insta@0.8.1
 source: crates/ra_ide_api/src/completion/completion_item.rs
 expression: kind_completions
@@ -19,6 +19,7 @@ expression: kind_completions
         delete: [79; 79),
         insert: "x",
         kind: Binding,
+        detail: "i32",
     },
     CompletionItem {
         label: "y",
@@ -26,5 +27,6 @@ expression: kind_completions
         delete: [79; 79),
         insert: "y",
         kind: Binding,
+        detail: "i32",
     },
 ]

crates/ra_ide_api/src/completion/snapshots/completion_item__dont_show_both_completions_for_shadowing.snap

@@ -1,5 +1,5 @@
 ---
-created: "2019-05-23T22:23:35.142044205Z"
+created: "2019-07-23T16:11:48.860949870Z"
 creator: insta@0.8.1
 source: crates/ra_ide_api/src/completion/completion_item.rs
 expression: kind_completions
@@ -11,6 +11,7 @@ expression: kind_completions
         delete: [126; 126),
         insert: "bar",
         kind: Binding,
+        detail: "i32",
     },
     CompletionItem {
         label: "foo",

crates/ra_ide_api/src/completion/snapshots/completion_item__self_in_methods.snap

@@ -1,5 +1,5 @@
 ---
-created: "2019-05-23T22:23:35.141900902Z"
+created: "2019-07-23T16:11:48.859812318Z"
 creator: insta@0.8.1
 source: crates/ra_ide_api/src/completion/completion_item.rs
 expression: kind_completions
@@ -18,5 +18,6 @@ expression: kind_completions
         delete: [25; 25),
         insert: "self",
         kind: Binding,
+        detail: "&{unknown}",
     },
 ]