3 files changed, 50 insertions, 1 deletions

diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 668d2fd72..8e830c8b8 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -362,6 +362,7 @@ fn on_request(
         .on::<req::References>(handlers::handle_references)?
         .on::<req::Formatting>(handlers::handle_formatting)?
         .on::<req::DocumentHighlightRequest>(handlers::handle_document_highlight)?
+        .on::<req::InlayHints>(handlers::handle_inlay_hints)?
         .finish();
     Ok(())
 }
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 68865b755..5bf950a53 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -21,7 +21,7 @@ use url_serde::Ser;
 use crate::{
     cargo_target_spec::{runnable_args, CargoTargetSpec},
     conv::{to_location, Conv, ConvWith, MapConvWith, TryConvWith, TryConvWithToVec},
-    req::{self, Decoration},
+    req::{self, Decoration, InlayHint, InlayHintsParams, InlayKind},
     world::WorldSnapshot,
     LspError, Result,
 };
@@ -874,3 +874,24 @@ fn to_diagnostic_severity(severity: Severity) -> DiagnosticSeverity {
         WeakWarning => DiagnosticSeverity::Hint,
     }
 }
+
+pub fn handle_inlay_hints(
+    world: WorldSnapshot,
+    params: InlayHintsParams,
+) -> Result<Vec<InlayHint>> {
+    let file_id = params.text_document.try_conv_with(&world)?;
+    let analysis = world.analysis();
+    let line_index = analysis.file_line_index(file_id);
+    Ok(analysis
+        .inlay_hints(file_id)?
+        .into_iter()
+        .map(|api_type| InlayHint {
+            label: api_type.label.to_string(),
+            range: api_type.range.conv_with(&line_index),
+            kind: match api_type.kind {
+                ra_ide_api::InlayKind::LetBindingType => InlayKind::LetBindingType,
+                ra_ide_api::InlayKind::ClosureParameterType => InlayKind::ClosureParameterType,
+            },
+        })
+        .collect())
+}
diff --git a/crates/ra_lsp_server/src/req.rs b/crates/ra_lsp_server/src/req.rs
index 8d39b04a7..916185f99 100644
--- a/crates/ra_lsp_server/src/req.rs
+++ b/crates/ra_lsp_server/src/req.rs
@@ -196,3 +196,30 @@ pub struct SourceChange {
     pub workspace_edit: WorkspaceEdit,
     pub cursor_position: Option<TextDocumentPositionParams>,
 }
+
+pub enum InlayHints {}
+
+impl Request for InlayHints {
+    type Params = InlayHintsParams;
+    type Result = Vec<InlayHint>;
+    const METHOD: &'static str = "rust-analyzer/inlayHints";
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct InlayHintsParams {
+    pub text_document: TextDocumentIdentifier,
+}
+
+#[derive(Debug, PartialEq, Eq, Deserialize, Serialize)]
+pub enum InlayKind {
+    LetBindingType,
+    ClosureParameterType,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct InlayHint {
+    pub range: Range,
+    pub kind: InlayKind,
+    pub label: String,
+}