feat: LSP inlay hints for let and global (#5510)

# Description

## Problem

Resolves #5513

## Summary

Shows type hints for `let` and `global`. Note that right now they will
always show for `let` and `global` that don't have an explicit type.
Eventually it would be nice to have a configuration to toggle them, but
the noise they introduce isn't that much so we could do that in a
separate PR (also paving the way for configuring other types of inlay
hints, like parameter names or names next to closing braces).


https://github.com/user-attachments/assets/4b743873-e1bf-430b-8632-4020ea53fbd8

## Additional Context

If you try it, hovering over types might not work well because of #5515,
so you could merge that branch into this one before testing things.

## Documentation

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>

compiler/noirc_errors/src/position.rs

@@ -90,6 +90,10 @@ impl Span {
         self.start() <= other.start() && self.end() >= other.end()
     }
 
+    pub fn intersects(&self, other: &Span) -> bool {
+        self.end() > other.start() && self.start() < other.end()
+    }
+
     pub fn is_smaller(&self, other: &Span) -> bool {
         let self_distance = self.end() - self.start();
         let other_distance = other.end() - other.start();

tooling/lsp/Cargo.toml

@@ -13,6 +13,7 @@ license.workspace = true
 acvm.workspace = true
 codespan-lsp.workspace = true
 lsp-types.workspace = true
+lsp_types_0_88_0 = { package = "lsp-types", version = "0.88.0" }
 nargo.workspace = true
 nargo_fmt.workspace = true
 nargo_toml.workspace = true

tooling/lsp/src/lib.rs

@@ -21,7 +21,7 @@ use async_lsp::{
 use fm::{codespan_files as files, FileManager};
 use fxhash::FxHashSet;
 use lsp_types::{
-    request::{HoverRequest, PrepareRenameRequest, References, Rename},
+    request::{HoverRequest, InlayHintRequest, PrepareRenameRequest, References, Rename},
     CodeLens,
 };
 use nargo::{
@@ -46,9 +46,9 @@ use notifications::{
 };
 use requests::{
     on_code_lens_request, on_formatting, on_goto_declaration_request, on_goto_definition_request,
-    on_goto_type_definition_request, on_hover_request, on_initialize, on_prepare_rename_request,
-    on_profile_run_request, on_references_request, on_rename_request, on_shutdown,
-    on_test_run_request, on_tests_request,
+    on_goto_type_definition_request, on_hover_request, on_initialize, on_inlay_hint_request,
+    on_prepare_rename_request, on_profile_run_request, on_references_request, on_rename_request,
+    on_shutdown, on_test_run_request, on_tests_request,
 };
 use serde_json::Value as JsonValue;
 use thiserror::Error;
@@ -130,6 +130,7 @@ impl NargoLspService {
             .request::<PrepareRenameRequest, _>(on_prepare_rename_request)
             .request::<Rename, _>(on_rename_request)
             .request::<HoverRequest, _>(on_hover_request)
+            .request::<InlayHintRequest, _>(on_inlay_hint_request)
             .notification::<notification::Initialized>(on_initialized)
             .notification::<notification::DidChangeConfiguration>(on_did_change_configuration)
             .notification::<notification::DidOpenTextDocument>(on_did_open_text_document)

tooling/lsp/src/requests/goto_definition.rs

@@ -32,6 +32,11 @@ fn on_goto_definition_inner(
     process_request(state, params.text_document_position_params, |args| {
         args.interner
             .get_definition_location_from(args.location, return_type_location_instead)
+            .or_else(|| {
+                args.interner
+                    .reference_at_location(args.location)
+                    .map(|reference| args.interner.reference_location(reference))
+            })
             .and_then(|found_location| {
                 let file_id = found_location.file;
                 let definition_position =
@@ -202,4 +207,32 @@ mod goto_definition_tests {
     async fn goto_for_local_variable() {
         expect_goto_for_all_references("local_variable", "some_var", 0).await;
     }
+
+    #[test]
+    async fn goto_at_struct_definition_finds_same_struct() {
+        expect_goto(
+            "go_to_definition",
+            Position { line: 21, character: 7 }, // "Foo" in "struct Foo"
+            "src/main.nr",
+            Range {
+                start: Position { line: 21, character: 7 },
+                end: Position { line: 21, character: 10 },
+            },
+        )
+        .await;
+    }
+
+    #[test]
+    async fn goto_at_trait_definition_finds_same_trait() {
+        expect_goto(
+            "go_to_definition",
+            Position { line: 25, character: 6 }, // "Trait" in "trait Trait"
+            "src/main.nr",
+            Range {
+                start: Position { line: 25, character: 6 },
+                end: Position { line: 25, character: 11 },
+            },
+        )
+        .await;
+    }
 }