From c735b979ed6f60483a66808077e1e59062c8e36f Mon Sep 17 00:00:00 2001
From: cameron <cameron.studdstreet@gmail.com>
Date: Mon, 4 Apr 2022 13:51:51 +0100
Subject: [PATCH 1/4] complete pattern args based on type name

---
 crates/ide_completion/src/render/function.rs | 45 +++++++++++++++++++-
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/crates/ide_completion/src/render/function.rs b/crates/ide_completion/src/render/function.rs
index 85014717d6..82688cfae6 100644
--- a/crates/ide_completion/src/render/function.rs
+++ b/crates/ide_completion/src/render/function.rs
@@ -3,7 +3,7 @@
 use hir::{db::HirDatabase, AsAssocItem, HirDisplay};
 use ide_db::{SnippetCap, SymbolKind};
 use itertools::Itertools;
-use stdx::format_to;
+use stdx::{format_to, to_lower_snake_case};
 use syntax::SmolStr;
 
 use crate::{
@@ -135,7 +135,15 @@ pub(super) fn add_call_parens<'b>(
                             let ref_ = ref_of_param(ctx, text, param.ty());
                             f(&format_args!("${{{}:{}{}}}", index + offset, ref_, text))
                         }
-                        None => f(&format_args!("${{{}:_}}", index + offset,)),
+                        None => {
+                            let name = match param.ty().as_adt() {
+                                Some(adt) => {
+                                    to_lower_snake_case(&adt.name(ctx.db).as_text().unwrap())
+                                }
+                                None => "_".to_string(),
+                            };
+                            f(&format_args!("${{{}:{}}}", index + offset, name))
+                        }
                     }
                 });
             match self_param {
@@ -516,6 +524,39 @@ fn take_mutably(mut x: &i32) {}
 fn main() {
     take_mutably(${1:x})$0
 }
+"#,
+        );
+    }
+
+    #[test]
+    fn complete_pattern_args_with_type_name_if_adt() {
+        check_edit(
+            "qux",
+            r#"
+struct Foo {
+    bar: i32
+}
+
+fn qux(Foo { bar }: Foo) {
+    println!("{}", bar);
+}
+
+fn main() {
+  qu$0
+}
+"#,
+            r#"
+struct Foo {
+    bar: i32
+}
+
+fn qux(Foo { bar }: Foo) {
+    println!("{}", bar);
+}
+
+fn main() {
+  qux(${1:foo})$0
+}
 "#,
         );
     }

From 2137bdfca3adfb2cffb552eeec3f366c5950d223 Mon Sep 17 00:00:00 2001
From: cameron <cameron.studdstreet@gmail.com>
Date: Mon, 4 Apr 2022 14:28:15 +0100
Subject: [PATCH 2/4] remove unwarp on adt name

---
 crates/ide_completion/src/render/function.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/crates/ide_completion/src/render/function.rs b/crates/ide_completion/src/render/function.rs
index 82688cfae6..6032b28fc6 100644
--- a/crates/ide_completion/src/render/function.rs
+++ b/crates/ide_completion/src/render/function.rs
@@ -137,10 +137,12 @@ pub(super) fn add_call_parens<'b>(
                         }
                         None => {
                             let name = match param.ty().as_adt() {
-                                Some(adt) => {
-                                    to_lower_snake_case(&adt.name(ctx.db).as_text().unwrap())
-                                }
                                 None => "_".to_string(),
+                                Some(adt) => adt
+                                    .name(ctx.db)
+                                    .as_text()
+                                    .map(to_lower_snake_case)
+                                    .unwrap_or("_".to_string()),
                             };
                             f(&format_args!("${{{}:{}}}", index + offset, name))
                         }

From bb1c3a20b502c48b4d0952878f0280e579c8a6f7 Mon Sep 17 00:00:00 2001
From: cameron <cameron.studdstreet@gmail.com>
Date: Mon, 4 Apr 2022 14:30:49 +0100
Subject: [PATCH 3/4] fix type error

---
 crates/ide_completion/src/render/function.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/ide_completion/src/render/function.rs b/crates/ide_completion/src/render/function.rs
index 6032b28fc6..c0f38a8fcd 100644
--- a/crates/ide_completion/src/render/function.rs
+++ b/crates/ide_completion/src/render/function.rs
@@ -141,7 +141,7 @@ pub(super) fn add_call_parens<'b>(
                                 Some(adt) => adt
                                     .name(ctx.db)
                                     .as_text()
-                                    .map(to_lower_snake_case)
+                                    .map(|s| to_lower_snake_case(s.as_str()))
                                     .unwrap_or("_".to_string()),
                             };
                             f(&format_args!("${{{}:{}}}", index + offset, name))

From 37d2a8243fc23d84490090803a428cf130894b6d Mon Sep 17 00:00:00 2001
From: cameron1024 <cameron.studdstreet@gmail.com>
Date: Mon, 4 Apr 2022 13:33:14 +0100
Subject: [PATCH 4/4] Update crates/ide_completion/src/render/function.rs

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>
---
 crates/ide_completion/src/render/function.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/ide_completion/src/render/function.rs b/crates/ide_completion/src/render/function.rs
index c0f38a8fcd..2031eef049 100644
--- a/crates/ide_completion/src/render/function.rs
+++ b/crates/ide_completion/src/render/function.rs
@@ -142,7 +142,7 @@ pub(super) fn add_call_parens<'b>(
                                     .name(ctx.db)
                                     .as_text()
                                     .map(|s| to_lower_snake_case(s.as_str()))
-                                    .unwrap_or("_".to_string()),
+                                    .unwrap_or_else(|| "_".to_string()),
                             };
                             f(&format_args!("${{{}:{}}}", index + offset, name))
                         }