[ty] Inlay hint call argument location (#20349)

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ty_ide/src/goto.rs

@@ -855,7 +855,7 @@ fn convert_resolved_definitions_to_targets(
             }
             ty_python_semantic::ResolvedDefinition::FileWithRange(file_range) => {
                 // For file ranges, navigate to the specific range within the file
-                crate::NavigationTarget::new(file_range.file(), file_range.range())
+                crate::NavigationTarget::from(file_range)
             }
         })
         .collect()

crates/ty_ide/src/lib.rs

@@ -132,6 +132,20 @@ impl NavigationTarget {
     pub fn full_range(&self) -> TextRange {
         self.full_range
     }
+
+    pub fn full_file_range(&self) -> FileRange {
+        FileRange::new(self.file, self.full_range)
+    }
+}
+
+impl From<FileRange> for NavigationTarget {
+    fn from(value: FileRange) -> Self {
+        Self {
+            file: value.file(),
+            focus_range: value.range(),
+            full_range: value.range(),
+        }
+    }
 }
 
 /// Specifies the kind of reference operation.

crates/ty_python_semantic/src/types/ide_support.rs

@@ -958,6 +958,22 @@ pub struct CallSignatureDetails<'db> {
     pub argument_to_parameter_mapping: Vec<MatchedArgument<'db>>,
 }
 
+impl CallSignatureDetails<'_> {
+    fn get_definition_parameter_range(&self, db: &dyn Db, name: &str) -> Option<FileRange> {
+        let definition = self.signature.definition()?;
+        let file = definition.file(db);
+        let module_ref = parsed_module(db, file).load(db);
+
+        let parameters = match definition.kind(db) {
+            DefinitionKind::Function(node) => &node.node(&module_ref).parameters,
+            // TODO: lambda functions
+            _ => return None,
+        };
+
+        Some(FileRange::new(file, parameters.find(name)?.name().range))
+    }
+}
+
 /// Extract signature details from a function call expression.
 /// This function analyzes the callable being invoked and returns zero or more
 /// `CallSignatureDetails` objects, each representing one possible signature
@@ -1153,15 +1169,16 @@ pub fn find_active_signature_from_details(
 }
 
 #[derive(Default)]
-pub struct InlayHintFunctionArgumentDetails {
-    pub argument_names: HashMap<usize, String>,
+pub struct InlayHintCallArgumentDetails {
+    /// The position of the arguments mapped to their name and the range of the argument definition in the signature.
+    pub argument_names: HashMap<usize, (String, Option<FileRange>)>,
 }
 
-pub fn inlay_hint_function_argument_details<'db>(
+pub fn inlay_hint_call_argument_details<'db>(
     db: &'db dyn Db,
     model: &SemanticModel<'db>,
     call_expr: &ast::ExprCall,
-) -> Option<InlayHintFunctionArgumentDetails> {
+) -> Option<InlayHintCallArgumentDetails> {
     let signature_details = call_signature_details(db, model, call_expr);
 
     if signature_details.is_empty() {
@@ -1173,6 +1190,7 @@ pub fn inlay_hint_function_argument_details<'db>(
     let call_signature_details = signature_details.get(active_signature_index)?;
 
     let parameters = call_signature_details.signature.parameters();
+
     let mut argument_names = HashMap::new();
 
     for arg_index in 0..call_expr.arguments.args.len() {
@@ -1195,16 +1213,19 @@ pub fn inlay_hint_function_argument_details<'db>(
             continue;
         };
 
+        let parameter_label_offset =
+            call_signature_details.get_definition_parameter_range(db, param.name()?);
+
         // Only add hints for parameters that can be specified by name
         if !param.is_positional_only() && !param.is_variadic() && !param.is_keyword_variadic() {
             let Some(name) = param.name() else {
                 continue;
             };
-            argument_names.insert(arg_index, name.to_string());
+            argument_names.insert(arg_index, (name.to_string(), parameter_label_offset));
         }
     }
 
-    Some(InlayHintFunctionArgumentDetails { argument_names })
+    Some(InlayHintCallArgumentDetails { argument_names })
 }
 
 /// Find the text range of a specific parameter in function parameters by name.

crates/ty_server/src/server/api/requests/inlay_hints.rs

@@ -5,7 +5,8 @@ use lsp_types::{InlayHintParams, Url};
 use ty_ide::{InlayHintKind, InlayHintLabel, inlay_hints};
 use ty_project::ProjectDatabase;
 
-use crate::document::{RangeExt, TextSizeExt};
+use crate::PositionEncoding;
+use crate::document::{RangeExt, TextSizeExt, ToLink};
 use crate::server::api::traits::{
     BackgroundDocumentRequestHandler, RequestHandler, RetriableRequestHandler,
 };
@@ -57,7 +58,7 @@ impl BackgroundDocumentRequestHandler for InlayHintRequestHandler {
                         .position
                         .to_lsp_position(db, file, snapshot.encoding())?
                         .local_position(),
-                    label: inlay_hint_label(&hint.label),
+                    label: inlay_hint_label(&hint.label, db, snapshot.encoding()),
                     kind: Some(inlay_hint_kind(&hint.kind)),
                     tooltip: None,
                     padding_left: None,
@@ -81,12 +82,18 @@ fn inlay_hint_kind(inlay_hint_kind: &InlayHintKind) -> lsp_types::InlayHintKind
     }
 }
 
-fn inlay_hint_label(inlay_hint_label: &InlayHintLabel) -> lsp_types::InlayHintLabel {
+fn inlay_hint_label(
+    inlay_hint_label: &InlayHintLabel,
+    db: &ProjectDatabase,
+    encoding: PositionEncoding,
+) -> lsp_types::InlayHintLabel {
     let mut label_parts = Vec::new();
     for part in inlay_hint_label.parts() {
         label_parts.push(lsp_types::InlayHintLabelPart {
             value: part.text().into(),
-            location: None,
+            location: part
+                .target()
+                .and_then(|target| target.to_location(db, encoding)),
             tooltip: None,
             command: None,
         });

crates/ty_server/tests/e2e/inlay_hints.rs

@@ -59,7 +59,20 @@ y = foo(1)
         },
         "label": [
           {
-            "value": "a"
+            "value": "a",
+            "location": {
+              "uri": "file://<temp_dir>/src/foo.py",
+              "range": {
+                "start": {
+                  "line": 2,
+                  "character": 8
+                },
+                "end": {
+                  "line": 2,
+                  "character": 9
+                }
+              }
+            }
           },
           {
             "value": "="

crates/ty_wasm/src/lib.rs

@@ -19,7 +19,7 @@ use ty_ide::{
     InlayHintSettings, MarkupKind, RangedValue, document_highlights, goto_declaration,
     goto_definition, goto_references, goto_type_definition, hover, inlay_hints,
 };
-use ty_ide::{NavigationTargets, signature_help};
+use ty_ide::{NavigationTarget, NavigationTargets, signature_help};
 use ty_project::metadata::options::Options;
 use ty_project::metadata::value::ValueSource;
 use ty_project::watch::{ChangeEvent, ChangedKind, CreatedKind, DeletedKind};
@@ -469,7 +469,22 @@ impl Workspace {
         Ok(result
             .into_iter()
             .map(|hint| InlayHint {
-                markdown: hint.display().to_string(),
+                label: hint
+                    .label
+                    .into_parts()
+                    .into_iter()
+                    .map(|part| InlayHintLabelPart {
+                        location: part.target().map(|target| {
+                            location_link_from_navigation_target(
+                                target,
+                                &self.db,
+                                self.position_encoding,
+                                None,
+                            )
+                        }),
+                        label: part.into_text(),
+                    })
+                    .collect(),
                 position: Position::from_text_size(
                     hint.position,
                     &index,
@@ -639,19 +654,8 @@ fn map_targets_to_links(
 
     targets
         .into_iter()
-        .map(|target| LocationLink {
-            path: target.file().path(db).to_string(),
-            full_range: Range::from_file_range(
-                db,
-                FileRange::new(target.file(), target.full_range()),
-                position_encoding,
-            ),
-            selection_range: Some(Range::from_file_range(
-                db,
-                FileRange::new(target.file(), target.focus_range()),
-                position_encoding,
-            )),
-            origin_selection_range: Some(source_range),
+        .map(|target| {
+            location_link_from_navigation_target(&target, db, position_encoding, Some(source_range))
         })
         .collect()
 }
@@ -905,6 +909,7 @@ impl From<PositionEncoding> for ruff_source_file::PositionEncoding {
 }
 
 #[wasm_bindgen]
+#[derive(Clone)]
 pub struct LocationLink {
     /// The target file path
     #[wasm_bindgen(getter_with_clone)]
@@ -918,6 +923,24 @@ pub struct LocationLink {
     pub origin_selection_range: Option<Range>,
 }
 
+fn location_link_from_navigation_target(
+    target: &NavigationTarget,
+    db: &dyn Db,
+    position_encoding: PositionEncoding,
+    source_range: Option<Range>,
+) -> LocationLink {
+    LocationLink {
+        path: target.file().path(db).to_string(),
+        full_range: Range::from_file_range(db, target.full_file_range(), position_encoding),
+        selection_range: Some(Range::from_file_range(
+            db,
+            FileRange::new(target.file(), target.focus_range()),
+            position_encoding,
+        )),
+        origin_selection_range: source_range,
+    }
+}
+
 #[wasm_bindgen]
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Hover {
@@ -1032,16 +1055,25 @@ impl From<ty_ide::InlayHintKind> for InlayHintKind {
 }
 
 #[wasm_bindgen]
-#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InlayHint {
     #[wasm_bindgen(getter_with_clone)]
-    pub markdown: String,
+    pub label: Vec<InlayHintLabelPart>,
 
     pub position: Position,
 
     pub kind: InlayHintKind,
 }
 
+#[wasm_bindgen]
+#[derive(Clone)]
+pub struct InlayHintLabelPart {
+    #[wasm_bindgen(getter_with_clone)]
+    pub label: String,
+
+    #[wasm_bindgen(getter_with_clone)]
+    pub location: Option<LocationLink>,
+}
+
 #[wasm_bindgen]
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct SemanticToken {

playground/ty/src/Editor/Editor.tsx

@@ -28,6 +28,7 @@ import {
   DocumentHighlight,
   DocumentHighlightKind,
   InlayHintKind,
+  LocationLink,
   TextEdit,
 } from "ty_wasm";
 import { FileId, ReadonlyFiles } from "../Playground";
@@ -445,7 +446,10 @@ class PlaygroundServer
     return {
       dispose: () => {},
       hints: inlayHints.map((hint) => ({
-        label: hint.markdown,
+        label: hint.label.map((part) => ({
+          label: part.label,
+          // As of 2025-09-23, location isn't supported by Monaco which is why we don't set it
+        })),
         position: {
           lineNumber: hint.position.line,
           column: hint.position.column,
@@ -763,8 +767,7 @@ class PlaygroundServer
     return null;
   }
 
-  private mapNavigationTargets(links: any[]): languages.LocationLink[] {
-    const result = links.map((link) => {
+  private mapNavigationTarget(link: LocationLink): languages.LocationLink {
     const uri = Uri.parse(link.path);
 
     // Pre-create models to ensure peek definition works
@@ -811,9 +814,12 @@ class PlaygroundServer
       targetSelectionRange: targetSelection,
       originSelectionRange: originSelection,
     } as languages.LocationLink;
-    });
+  }
 
-    return result;
+  private mapNavigationTargets(
+    links: LocationLink[],
+  ): languages.LocationLink[] {
+    return links.map((link) => this.mapNavigationTarget(link));
   }
 
   dispose() {