1 files changed, 49 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closure_ret.rs b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closure_ret.rs
new file mode 100644
index 000000000..d9929beaa
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide/src/inlay_hints/closure_ret.rs
@@ -0,0 +1,49 @@
+//! Implementation of "closure return type" inlay hints.
+use ide_db::{base_db::FileId, famous_defs::FamousDefs};
+use syntax::ast::{self, AstNode};
+
+use crate::{
+    inlay_hints::closure_has_block_body, ClosureReturnTypeHints, InlayHint, InlayHintsConfig,
+    InlayKind, InlayTooltip,
+};
+
+use super::label_of_ty;
+
+pub(super) fn hints(
+    acc: &mut Vec<InlayHint>,
+    famous_defs @ FamousDefs(sema, _): &FamousDefs<'_, '_>,
+    config: &InlayHintsConfig,
+    file_id: FileId,
+    closure: ast::ClosureExpr,
+) -> Option<()> {
+    if config.closure_return_type_hints == ClosureReturnTypeHints::Never {
+        return None;
+    }
+
+    if closure.ret_type().is_some() {
+        return None;
+    }
+
+    if !closure_has_block_body(&closure)
+        && config.closure_return_type_hints == ClosureReturnTypeHints::WithBlock
+    {
+        return None;
+    }
+
+    let param_list = closure.param_list()?;
+
+    let closure = sema.descend_node_into_attributes(closure).pop()?;
+    let ty = sema.type_of_expr(&ast::Expr::ClosureExpr(closure))?.adjusted();
+    let callable = ty.as_callable(sema.db)?;
+    let ty = callable.return_type();
+    if ty.is_unit() {
+        return None;
+    }
+    acc.push(InlayHint {
+        range: param_list.syntax().text_range(),
+        kind: InlayKind::ClosureReturnTypeHint,
+        label: label_of_ty(famous_defs, config, ty)?,
+        tooltip: Some(InlayTooltip::HoverRanged(file_id, param_list.syntax().text_range())),
+    });
+    Some(())
+}