From 67495b618b1538e1e90f49ff6b8f980ca83c3aa9 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonas.schievink@ferrous-systems.com>
Date: Thu, 7 Apr 2022 15:47:03 +0200
Subject: [PATCH 1/2] Fix panics with `#[cfg]`'d-out `self` parameter

---
 crates/hir_def/src/data.rs            |  9 +++++++++
 crates/hir_ty/src/tests/regression.rs | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/crates/hir_def/src/data.rs b/crates/hir_def/src/data.rs
index 8e0bb0c34d..6571b2a927 100644
--- a/crates/hir_def/src/data.rs
+++ b/crates/hir_def/src/data.rs
@@ -56,6 +56,15 @@ impl FunctionData {
         if is_varargs {
             flags.bits |= FnFlags::IS_VARARGS;
         }
+        if flags.bits & FnFlags::HAS_SELF_PARAM != 0 {
+            // If there's a self param in the syntax, but it is cfg'd out, remove the flag.
+            cov_mark::hit!(cfgd_out_self_param);
+            let param =
+                func.params.clone().next().expect("fn HAS_SELF_PARAM but no parameters allocated");
+            if !item_tree.attrs(db, krate, param.into()).is_cfg_enabled(cfg_options) {
+                flags.bits &= !FnFlags::HAS_SELF_PARAM;
+            }
+        }
 
         let legacy_const_generics_indices = item_tree
             .attrs(db, krate, ModItem::from(loc.id.value).into())
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index be2b733a4b..37f321a0f0 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -1488,3 +1488,20 @@ fn test<T: Crash>() {
 "#,
     );
 }
+
+#[test]
+fn cfgd_out_self_param() {
+    cov_mark::check!(cfgd_out_self_param);
+    check_no_mismatches(
+        r#"
+struct S;
+impl S {
+    fn f(#[cfg(never)] &self) {}
+}
+
+fn f(s: S) {
+    s.f();
+}
+"#,
+    );
+}

From 16d0f724b6544a87148e5fc34e251af41ac63da5 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonas.schievink@ferrous-systems.com>
Date: Thu, 7 Apr 2022 15:55:44 +0200
Subject: [PATCH 2/2] use stdx::never

---
 crates/hir_def/src/data.rs | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/crates/hir_def/src/data.rs b/crates/hir_def/src/data.rs
index 6571b2a927..5140a9d4ca 100644
--- a/crates/hir_def/src/data.rs
+++ b/crates/hir_def/src/data.rs
@@ -58,10 +58,17 @@ impl FunctionData {
         }
         if flags.bits & FnFlags::HAS_SELF_PARAM != 0 {
             // If there's a self param in the syntax, but it is cfg'd out, remove the flag.
-            cov_mark::hit!(cfgd_out_self_param);
-            let param =
-                func.params.clone().next().expect("fn HAS_SELF_PARAM but no parameters allocated");
-            if !item_tree.attrs(db, krate, param.into()).is_cfg_enabled(cfg_options) {
+            let is_cfgd_out = match func.params.clone().next() {
+                Some(param) => {
+                    !item_tree.attrs(db, krate, param.into()).is_cfg_enabled(cfg_options)
+                }
+                None => {
+                    stdx::never!("fn HAS_SELF_PARAM but no parameters allocated");
+                    true
+                }
+            };
+            if is_cfgd_out {
+                cov_mark::hit!(cfgd_out_self_param);
                 flags.bits &= !FnFlags::HAS_SELF_PARAM;
             }
         }