feat: Closure capture inlay hints

crates/ide/src/inlay_hints/closure_captures.rs

@@ -0,0 +1,193 @@
+//! Implementation of "closure return type" inlay hints.
+//!
+//! Tests live in [`bind_pat`][super::bind_pat] module.
+use ide_db::{base_db::FileId, famous_defs::FamousDefs};
+use syntax::ast::{self, AstNode};
+use text_edit::{TextRange, TextSize};
+
+use crate::{InlayHint, InlayHintLabel, InlayHintsConfig, InlayKind};
+
+pub(super) fn hints(
+    acc: &mut Vec<InlayHint>,
+    FamousDefs(sema, _): &FamousDefs<'_, '_>,
+    config: &InlayHintsConfig,
+    _file_id: FileId,
+    closure: ast::ClosureExpr,
+) -> Option<()> {
+    if !config.closure_capture_hints {
+        return None;
+    }
+    let ty = &sema.type_of_expr(&closure.clone().into())?.original;
+    let c = ty.as_closure()?;
+    let captures = c.captured_items(sema.db);
+
+    if captures.is_empty() {
+        return None;
+    }
+
+    let move_kw_range = match closure.move_token() {
+        Some(t) => t.text_range(),
+        None => {
+            let range = closure.syntax().first_token()?.prev_token()?.text_range();
+            let range = TextRange::new(range.end() - TextSize::from(1), range.end());
+            acc.push(InlayHint {
+                range,
+                kind: InlayKind::ClosureCapture,
+                label: InlayHintLabel::simple("move", None, None),
+                text_edit: None,
+            });
+            range
+        }
+    };
+    acc.push(InlayHint {
+        range: move_kw_range,
+        kind: InlayKind::ClosureCapture,
+        label: InlayHintLabel::from("("),
+        text_edit: None,
+    });
+    let last = captures.len() - 1;
+    for (idx, capture) in captures.into_iter().enumerate() {
+        let local = capture.local();
+        let source = local.primary_source(sema.db);
+
+        // force cache the source file, otherwise sema lookup will potentially panic
+        _ = sema.parse_or_expand(source.file());
+
+        acc.push(InlayHint {
+            range: move_kw_range,
+            kind: InlayKind::ClosureCapture,
+            label: InlayHintLabel::simple(
+                format!(
+                    "{}{}",
+                    match capture.kind() {
+                        hir::CaptureKind::SharedRef => "&",
+                        hir::CaptureKind::UniqueSharedRef => "&unique ",
+                        hir::CaptureKind::MutableRef => "&mut ",
+                        hir::CaptureKind::Move => "",
+                    },
+                    local.name(sema.db)
+                ),
+                None,
+                source.name().and_then(|name| sema.original_range_opt(name.syntax())),
+            ),
+            text_edit: None,
+        });
+
+        if idx != last {
+            acc.push(InlayHint {
+                range: move_kw_range,
+                kind: InlayKind::ClosureCapture,
+                label: InlayHintLabel::simple(", ", None, None),
+                text_edit: None,
+            });
+        }
+    }
+    acc.push(InlayHint {
+        range: move_kw_range,
+        kind: InlayKind::ClosureCapture,
+        label: InlayHintLabel::from(")"),
+        text_edit: None,
+    });
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{
+        inlay_hints::tests::{check_with_config, DISABLED_CONFIG},
+        InlayHintsConfig,
+    };
+
+    #[test]
+    fn all_capture_kinds() {
+        check_with_config(
+            InlayHintsConfig { closure_capture_hints: true, ..DISABLED_CONFIG },
+            r#"
+//- minicore: copy, derive
+
+
+#[derive(Copy, Clone)]
+struct Copy;
+
+struct NonCopy;
+
+fn main() {
+    let foo = Copy;
+    let bar = NonCopy;
+    let mut baz = NonCopy;
+    let qux = &mut NonCopy;
+    || {
+// ^ move
+// ^ (
+// ^ &foo
+// ^ ,
+// ^ bar
+// ^ ,
+// ^ baz
+// ^ ,
+// ^ qux
+// ^ )
+        foo;
+        bar;
+        baz;
+        qux;
+    };
+    || {
+// ^ move
+// ^ (
+// ^ &foo
+// ^ ,
+// ^ &bar
+// ^ ,
+// ^ &baz
+// ^ ,
+// ^ &qux
+// ^ )
+        &foo;
+        &bar;
+        &baz;
+        &qux;
+    };
+    || {
+// ^ move
+// ^ (
+// ^ &mut baz
+// ^ )
+        &mut baz;
+    };
+    // FIXME: &mut qux should be &unique qux
+    || {
+// ^ move
+// ^ (
+// ^ &mut baz
+// ^ ,
+// ^ &mut qux
+// ^ )
+        baz = NonCopy;
+        *qux = NonCopy;
+    };
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_token() {
+        check_with_config(
+            InlayHintsConfig { closure_capture_hints: true, ..DISABLED_CONFIG },
+            r#"
+//- minicore: copy, derive
+fn main() {
+    let foo = u32;
+    move || {
+//  ^^^^ (
+//  ^^^^ foo
+//  ^^^^ )
+        foo;
+    };
+}
+"#,
+        );
+    }
+}