[ty] Clarify what "cursor" means

This commit does a small refactor to combine the file and
cursor offset into a single type. I think this makes it
clearer that even if there are multiple files in the cursor
test, this one in particular corresponds to the file that
contains the `<CURSOR>` marker.

crates/ty_ide/src/completion.rs

@@ -2184,7 +2184,7 @@ importlib.<CURSOR>
         }
 
         fn completions_if(&self, predicate: impl Fn(&str) -> bool) -> String {
-            let completions = completion(&self.db, self.file, self.cursor_offset);
+            let completions = completion(&self.db, self.cursor.file, self.cursor.offset);
             if completions.is_empty() {
                 return "<No completions found>".to_string();
             }
@@ -2198,7 +2198,7 @@ importlib.<CURSOR>
 
         #[track_caller]
         fn assert_completions_include(&self, expected: &str) {
-            let completions = completion(&self.db, self.file, self.cursor_offset);
+            let completions = completion(&self.db, self.cursor.file, self.cursor.offset);
 
             assert!(
                 completions
@@ -2210,7 +2210,7 @@ importlib.<CURSOR>
 
         #[track_caller]
         fn assert_completions_do_not_include(&self, unexpected: &str) {
-            let completions = completion(&self.db, self.file, self.cursor_offset);
+            let completions = completion(&self.db, self.cursor.file, self.cursor.offset);
 
             assert!(
                 completions

crates/ty_ide/src/goto.rs

@@ -833,7 +833,8 @@ f(**kwargs<CURSOR>)
 
     impl CursorTest {
         fn goto_type_definition(&self) -> String {
-            let Some(targets) = goto_type_definition(&self.db, self.file, self.cursor_offset)
+            let Some(targets) =
+                goto_type_definition(&self.db, self.cursor.file, self.cursor.offset)
             else {
                 return "No goto target found".to_string();
             };

crates/ty_ide/src/hover.rs

@@ -737,7 +737,7 @@ mod tests {
         fn hover(&self) -> String {
             use std::fmt::Write;
 
-            let Some(hover) = hover(&self.db, self.file, self.cursor_offset) else {
+            let Some(hover) = hover(&self.db, self.cursor.file, self.cursor.offset) else {
                 return "Hover provided no content".to_string();
             };
 
@@ -769,7 +769,7 @@ mod tests {
             );
             diagnostic.annotate(
                 Annotation::secondary(
-                    Span::from(source.file()).with_range(TextRange::empty(self.cursor_offset)),
+                    Span::from(source.file()).with_range(TextRange::empty(self.cursor.offset)),
                 )
                 .message("Cursor offset"),
             );

crates/ty_ide/src/lib.rs

@@ -213,14 +213,17 @@ mod tests {
         SearchPathSettings,
     };
 
+    /// A way to create a simple single-file (named `main.py`) cursor test.
+    ///
+    /// Use cases that require multiple files with a `<CURSOR>` marker
+    /// in a file other than `main.py` can use `CursorTest::builder()`.
     pub(super) fn cursor_test(source: &str) -> CursorTest {
         CursorTest::builder().source("main.py", source).build()
     }
 
     pub(super) struct CursorTest {
         pub(super) db: TestDb,
-        pub(super) cursor_offset: TextSize,
+        pub(super) cursor: Cursor,
-        pub(super) file: File,
         _insta_settings_guard: SettingsBindDropGuard,
     }
 
@@ -258,6 +261,8 @@ mod tests {
         }
     }
 
+    /// The file and offset into that file containing
+    /// a `<CURSOR>` marker.
     pub(super) struct Cursor {
         pub(super) file: File,
         pub(super) offset: TextSize,
@@ -318,13 +323,10 @@ mod tests {
             insta_settings.add_filter(r"@Todo\(.+\)", "@Todo");
 
             let insta_settings_guard = insta_settings.bind_to_scope();
-            let Cursor { file, offset } =
-                cursor.expect("at least one source to contain `<CURSOR>`");
 
             CursorTest {
                 db,
-                cursor_offset: offset,
+                cursor: cursor.expect("at least one source to contain `<CURSOR>`"),
-                file,
                 _insta_settings_guard: insta_settings_guard,
             }
         }