Merge #11445

11445: Upstream inlay hints r=lnicola a=lnicola

Closes https://github.com/rust-analyzer/rust-analyzer/issues/2797
Closes https://github.com/rust-analyzer/rust-analyzer/issues/3394 (since now resolve the hints for the range given only, not for the whole document. We don't actually resolve anything due to [hard requirement](https://github.com/rust-analyzer/rust-analyzer/pull/11445#issuecomment-1035227434) on label being immutable. Any further heavy actions could go to the `resolve` method that's now available via the official Code API for hints)

Based on `@SomeoneToIgnore's` branch, with a couple of updates:

 - I squashed, more or less successfully, the commits on that branch
 - downloading the `.d.ts` no longer works, but you can get it manually from https://raw.githubusercontent.com/microsoft/vscode/release/1.64/src/vscode-dts/vscode.proposed.inlayHints.d.ts
 - you might need to pass `--enable-proposed-api matklad.rust-analyzer`
 - if I'm reading the definition right, `InlayHintKind` needs to be serialized as a number, not string
 - this doesn't work anyway -- the client-side gets the hints, but they don't display

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Laurențiu Nicola <lnicola@dend.ro>

crates/rust-analyzer/src/caps.rs

@@ -115,6 +115,7 @@ pub fn server_capabilities(config: &Config) -> ServerCapabilities {
         experimental: Some(json!({
             "externalDocs": true,
             "hoverRange": true,
+            "inlayHints": true,
             "joinLines": true,
             "matchingBrace": true,
             "moveItem": true,

crates/rust-analyzer/src/handlers.rs

@@ -1318,11 +1318,22 @@ pub(crate) fn handle_inlay_hints(
     params: InlayHintsParams,
 ) -> Result<Vec<InlayHint>> {
     let _p = profile::span("handle_inlay_hints");
-    let file_id = from_proto::file_id(&snap, &params.text_document.uri)?;
+    let document_uri = &params.text_document.uri;
+    let file_id = from_proto::file_id(&snap, document_uri)?;
     let line_index = snap.file_line_index(file_id)?;
+    let range = params
+        .range
+        .map(|range| {
+            from_proto::file_range(
+                &snap,
+                TextDocumentIdentifier::new(document_uri.to_owned()),
+                range,
+            )
+        })
+        .transpose()?;
     Ok(snap
         .analysis
-        .inlay_hints(&snap.config.inlay_hints(), file_id)?
+        .inlay_hints(&snap.config.inlay_hints(), file_id, range)?
         .into_iter()
         .map(|it| to_proto::inlay_hint(&line_index, it))
         .collect())

crates/rust-analyzer/src/lsp_ext.rs

@@ -233,27 +233,34 @@ pub enum InlayHints {}
 impl Request for InlayHints {
     type Params = InlayHintsParams;
     type Result = Vec<InlayHint>;
-    const METHOD: &'static str = "rust-analyzer/inlayHints";
+    const METHOD: &'static str = "experimental/inlayHints";
 }
 
 #[derive(Serialize, Deserialize, Debug)]
 #[serde(rename_all = "camelCase")]
 pub struct InlayHintsParams {
     pub text_document: TextDocumentIdentifier,
+    pub range: Option<lsp_types::Range>,
 }
 
-#[derive(Debug, PartialEq, Eq, Deserialize, Serialize)]
-pub enum InlayKind {
-    TypeHint,
-    ParameterHint,
-    ChainingHint,
+#[derive(Eq, PartialEq, Debug, Copy, Clone, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct InlayHintKind(u8);
+
+impl InlayHintKind {
+    pub const TYPE: InlayHintKind = InlayHintKind(1);
+    pub const PARAMETER: InlayHintKind = InlayHintKind(2);
 }
 
 #[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
 pub struct InlayHint {
-    pub range: Range,
-    pub kind: InlayKind,
     pub label: String,
+    pub position: Position,
+    pub kind: Option<InlayHintKind>,
+    pub tooltip: Option<String>,
+    pub padding_left: Option<bool>,
+    pub padding_right: Option<bool>,
 }
 
 pub enum Ssr {}

crates/rust-analyzer/src/to_proto.rs

@@ -416,12 +416,18 @@ pub(crate) fn signature_help(
 pub(crate) fn inlay_hint(line_index: &LineIndex, inlay_hint: InlayHint) -> lsp_ext::InlayHint {
     lsp_ext::InlayHint {
         label: inlay_hint.label.to_string(),
-        range: range(line_index, inlay_hint.range),
-        kind: match inlay_hint.kind {
-            InlayKind::ParameterHint => lsp_ext::InlayKind::ParameterHint,
-            InlayKind::TypeHint => lsp_ext::InlayKind::TypeHint,
-            InlayKind::ChainingHint => lsp_ext::InlayKind::ChainingHint,
+        position: match inlay_hint.kind {
+            InlayKind::ParameterHint => position(line_index, inlay_hint.range.start()),
+            _ => position(line_index, inlay_hint.range.end()),
         },
+        kind: match inlay_hint.kind {
+            InlayKind::ParameterHint => Some(lsp_ext::InlayHintKind::PARAMETER),
+            InlayKind::TypeHint => Some(lsp_ext::InlayHintKind::TYPE),
+            InlayKind::ChainingHint => None,
+        },
+        tooltip: None,
+        padding_left: Some(true),
+        padding_right: Some(true),
     }
 }