From 49dd6c321dbf1b8c41479f9eb275e5bd3d890aae Mon Sep 17 00:00:00 2001
From: tyranron <tyranron@gmail.com>
Date: Wed, 28 Aug 2024 15:59:31 +0300
Subject: [PATCH] Add `#[allow(unreachable_code)]` to `Display` and `Debug`
 derives

---
 impl/src/fmt/debug.rs   |  1 +
 impl/src/fmt/display.rs |  1 +
 tests/debug.rs          | 50 ++++++++++++++++++++++++++++++++++++++
 tests/display.rs        | 54 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 106 insertions(+)

diff --git a/impl/src/fmt/debug.rs b/impl/src/fmt/debug.rs
index a3cee6f2..199b9b0f 100644
--- a/impl/src/fmt/debug.rs
+++ b/impl/src/fmt/debug.rs
@@ -60,6 +60,7 @@ pub fn expand(input: &syn::DeriveInput, _: &str) -> syn::Result<TokenStream> {
     };
 
     Ok(quote! {
+        #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
         #[automatically_derived]
         impl #impl_gens derive_more::Debug for #ident #ty_gens #where_clause {
             #[inline]
diff --git a/impl/src/fmt/display.rs b/impl/src/fmt/display.rs
index b217a779..41320df5 100644
--- a/impl/src/fmt/display.rs
+++ b/impl/src/fmt/display.rs
@@ -62,6 +62,7 @@ pub fn expand(input: &syn::DeriveInput, trait_name: &str) -> syn::Result<TokenSt
     };
 
     Ok(quote! {
+        #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
         #[automatically_derived]
         impl #impl_gens derive_more::#trait_ident for #ident #ty_gens #where_clause {
             fn fmt(
diff --git a/tests/debug.rs b/tests/debug.rs
index d88903b3..aa886b01 100644
--- a/tests/debug.rs
+++ b/tests/debug.rs
@@ -1,4 +1,5 @@
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(nightly, feature(never_type))]
 #![allow(dead_code)] // some code is tested for type checking only
 
 #[cfg(not(feature = "std"))]
@@ -417,6 +418,19 @@ mod structs {
                 }
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use derive_more::Debug;
+
+            #[derive(Debug)]
+            struct Tuple(!);
+
+            #[derive(Debug)]
+            struct Struct {
+                field: !,
+            }
+        }
     }
 
     mod multi_field {
@@ -676,6 +690,20 @@ mod structs {
                 );
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use derive_more::Debug;
+
+            #[derive(Debug)]
+            struct Tuple(i32, !);
+
+            #[derive(Debug)]
+            struct Struct {
+                field: !,
+                other: i32,
+            }
+        }
     }
 }
 
@@ -980,6 +1008,17 @@ mod enums {
                 }
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use derive_more::Debug;
+
+            #[derive(Debug)]
+            enum Enum {
+                Unnamed(!),
+                Named { field: ! },
+            }
+        }
     }
 
     mod multi_field_variant {
@@ -1155,6 +1194,17 @@ mod enums {
                 );
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use derive_more::Debug;
+
+            #[derive(Debug)]
+            enum Enum {
+                Unnamed(i32, !),
+                Named { field: !, other: i32 },
+            }
+        }
     }
 }
 
diff --git a/tests/display.rs b/tests/display.rs
index c3cf1c14..a7257237 100644
--- a/tests/display.rs
+++ b/tests/display.rs
@@ -1,4 +1,5 @@
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(nightly, feature(never_type))]
 #![allow(dead_code)] // some code is tested for type checking only
 
 #[cfg(not(feature = "std"))]
@@ -528,6 +529,19 @@ mod structs {
                 }
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use super::*;
+
+            #[derive(Display)]
+            struct Tuple(!);
+
+            #[derive(Display)]
+            struct Struct {
+                field: !,
+            }
+        }
     }
 
     mod multi_field {
@@ -682,6 +696,22 @@ mod structs {
                 }
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use super::*;
+
+            #[derive(Display)]
+            #[display("{_0}")]
+            struct Tuple(i32, !);
+
+            #[derive(Display)]
+            #[display("{field}")]
+            struct Struct {
+                field: !,
+                other: i32,
+            }
+        }
     }
 }
 
@@ -1154,6 +1184,17 @@ mod enums {
                 }
             }
         }
+
+        #[cfg(nightly)]
+        mod never {
+            use super::*;
+
+            #[derive(Display)]
+            enum Enum {
+                Unnamed(!),
+                Named { field: ! },
+            }
+        }
     }
 
     mod multi_field_variant {
@@ -1314,6 +1355,19 @@ mod enums {
             }
         }
 
+        #[cfg(nightly)]
+        mod never {
+            use super::*;
+
+            #[derive(Display)]
+            enum Enum {
+                #[display("{_0}")]
+                Unnamed(i32, !),
+                #[display("{field}")]
+                Named { field: !, other: i32 },
+            }
+        }
+
         mod shared_format {
             use super::*;