3 files changed, 18 insertions, 0 deletions

diff --git a/crates/hir_def/src/data.rs b/crates/hir_def/src/data.rs
index ff1ef0df6..733db2eac 100644
--- a/crates/hir_def/src/data.rs
+++ b/crates/hir_def/src/data.rs
@@ -19,6 +19,7 @@ use crate::{
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FunctionData {
     pub name: Name,
+    pub param_names: Vec<Option<Name>>,
     pub params: Vec<TypeRef>,
     pub ret_type: TypeRef,
     pub attrs: Attrs,
@@ -39,6 +40,7 @@ impl FunctionData {
 
         Arc::new(FunctionData {
             name: func.name.clone(),
+            param_names: func.param_names.to_vec(),
             params: func.params.to_vec(),
             ret_type: func.ret_type.clone(),
             attrs: item_tree.attrs(ModItem::from(loc.id.value).into()).clone(),
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 8a1121bbd..ca502ce2b 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -507,6 +507,8 @@ pub struct Function {
     pub has_self_param: bool,
     pub has_body: bool,
     pub is_unsafe: bool,
+    /// List of function parameters names. Does not include `self`.
+    pub param_names: Box<[Option<Name>]>,
     pub params: Box<[TypeRef]>,
     pub is_varargs: bool,
     pub ret_type: TypeRef,
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 3328639cf..2ffa46ac0 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -283,6 +283,7 @@ impl Ctx {
         let name = func.name()?.as_name();
 
         let mut params = Vec::new();
+        let mut param_names = Vec::new();
         let mut has_self_param = false;
         if let Some(param_list) = func.param_list() {
             if let Some(self_param) = param_list.self_param() {
@@ -305,6 +306,18 @@ impl Ctx {
                 has_self_param = true;
             }
             for param in param_list.params() {
+                let param_name = param
+                    .pat()
+                    .map(|name| {
+                        if let ast::Pat::IdentPat(ident) = name {
+                            Some(ident.name()?.as_name())
+                        } else {
+                            None
+                        }
+                    })
+                    .flatten();
+                param_names.push(param_name);
+
                 let type_ref = TypeRef::from_ast_opt(&self.body_ctx, param.ty());
                 params.push(type_ref);
             }
@@ -341,6 +354,7 @@ impl Ctx {
             has_body,
             is_unsafe: func.unsafe_token().is_some(),
             params: params.into_boxed_slice(),
+            param_names: param_names.into_boxed_slice(),
             is_varargs,
             ret_type,
             ast_id,