expand/resolve: Turn #[derive] into a regular macro attribute

src/test/ui/proc-macro/attribute-after-derive.rs

@@ -0,0 +1,28 @@
+// Macro attributes are allowed after `#[derive]` and
+// `#[derive]` fully configures the item for following attributes.
+
+// check-pass
+// compile-flags: -Z span-debug
+// aux-build: test-macros.rs
+
+#![no_std] // Don't load unnecessary hygiene information from std
+extern crate std;
+
+#[macro_use]
+extern crate test_macros;
+
+#[print_attr]
+#[derive(Print)]
+struct AttributeDerive {
+    #[cfg(FALSE)]
+    field: u8,
+}
+
+#[derive(Print)]
+#[print_attr]
+struct DeriveAttribute {
+    #[cfg(FALSE)]
+    field: u8,
+}
+
+fn main() {}

src/test/ui/proc-macro/attribute-after-derive.stdout

@@ -0,0 +1,148 @@
+PRINT-ATTR INPUT (DISPLAY): #[derive(Print)] struct AttributeDerive { #[cfg(FALSE)] field : u8, }
+PRINT-ATTR INPUT (DEBUG): TokenStream [
+    Punct {
+        ch: '#',
+        spacing: Alone,
+        span: $DIR/attribute-after-derive.rs:15:1: 15:2 (#0),
+    },
+    Group {
+        delimiter: Bracket,
+        stream: TokenStream [
+            Ident {
+                ident: "derive",
+                span: $DIR/attribute-after-derive.rs:15:3: 15:9 (#0),
+            },
+            Group {
+                delimiter: Parenthesis,
+                stream: TokenStream [
+                    Ident {
+                        ident: "Print",
+                        span: $DIR/attribute-after-derive.rs:15:10: 15:15 (#0),
+                    },
+                ],
+                span: $DIR/attribute-after-derive.rs:15:9: 15:16 (#0),
+            },
+        ],
+        span: $DIR/attribute-after-derive.rs:15:2: 15:17 (#0),
+    },
+    Ident {
+        ident: "struct",
+        span: $DIR/attribute-after-derive.rs:16:1: 16:7 (#0),
+    },
+    Ident {
+        ident: "AttributeDerive",
+        span: $DIR/attribute-after-derive.rs:16:8: 16:23 (#0),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [
+            Punct {
+                ch: '#',
+                spacing: Alone,
+                span: $DIR/attribute-after-derive.rs:17:5: 17:6 (#0),
+            },
+            Group {
+                delimiter: Bracket,
+                stream: TokenStream [
+                    Ident {
+                        ident: "cfg",
+                        span: $DIR/attribute-after-derive.rs:17:7: 17:10 (#0),
+                    },
+                    Group {
+                        delimiter: Parenthesis,
+                        stream: TokenStream [
+                            Ident {
+                                ident: "FALSE",
+                                span: $DIR/attribute-after-derive.rs:17:11: 17:16 (#0),
+                            },
+                        ],
+                        span: $DIR/attribute-after-derive.rs:17:10: 17:17 (#0),
+                    },
+                ],
+                span: $DIR/attribute-after-derive.rs:17:6: 17:18 (#0),
+            },
+            Ident {
+                ident: "field",
+                span: $DIR/attribute-after-derive.rs:18:5: 18:10 (#0),
+            },
+            Punct {
+                ch: ':',
+                spacing: Alone,
+                span: $DIR/attribute-after-derive.rs:18:10: 18:11 (#0),
+            },
+            Ident {
+                ident: "u8",
+                span: $DIR/attribute-after-derive.rs:18:12: 18:14 (#0),
+            },
+            Punct {
+                ch: ',',
+                spacing: Alone,
+                span: $DIR/attribute-after-derive.rs:18:14: 18:15 (#0),
+            },
+        ],
+        span: $DIR/attribute-after-derive.rs:16:24: 19:2 (#0),
+    },
+]
+PRINT-DERIVE INPUT (DISPLAY): struct AttributeDerive { }
+PRINT-DERIVE INPUT (DEBUG): TokenStream [
+    Ident {
+        ident: "struct",
+        span: $DIR/attribute-after-derive.rs:16:1: 19:2 (#0),
+    },
+    Ident {
+        ident: "AttributeDerive",
+        span: $DIR/attribute-after-derive.rs:16:1: 19:2 (#0),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [],
+        span: $DIR/attribute-after-derive.rs:16:1: 19:2 (#0),
+    },
+]
+PRINT-ATTR INPUT (DISPLAY): struct DeriveAttribute { }
+PRINT-ATTR INPUT (DEBUG): TokenStream [
+    Ident {
+        ident: "struct",
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Ident {
+        ident: "DeriveAttribute",
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [],
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+]
+PRINT-DERIVE INPUT (DISPLAY): #[print_attr] struct DeriveAttribute { }
+PRINT-DERIVE INPUT (DEBUG): TokenStream [
+    Punct {
+        ch: '#',
+        spacing: Alone,
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Group {
+        delimiter: Bracket,
+        stream: TokenStream [
+            Ident {
+                ident: "print_attr",
+                span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+            },
+        ],
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Ident {
+        ident: "struct",
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Ident {
+        ident: "DeriveAttribute",
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [],
+        span: $DIR/attribute-after-derive.rs:23:1: 26:2 (#0),
+    },
+]

src/test/ui/proc-macro/attribute-order-restricted.rs

@@ -1,14 +0,0 @@
-// aux-build:test-macros.rs
-
-#[macro_use]
-extern crate test_macros;
-
-#[identity_attr] // OK
-#[derive(Clone)]
-struct Before;
-
-#[derive(Clone)]
-#[identity_attr] //~ ERROR macro attributes must be placed before `#[derive]`
-struct After;
-
-fn main() {}

src/test/ui/proc-macro/attribute-order-restricted.stderr

@@ -1,8 +0,0 @@
-error: macro attributes must be placed before `#[derive]`
-  --> $DIR/attribute-order-restricted.rs:11:1
-   |
-LL | #[identity_attr]
-   | ^^^^^^^^^^^^^^^^
-
-error: aborting due to previous error
-

src/test/ui/proc-macro/derive-helper-shadowing.rs

@@ -17,6 +17,8 @@ macro_rules! gen_helper_use {
 }
 
 #[empty_helper] //~ ERROR `empty_helper` is ambiguous
+                //~| WARN derive helper attribute is used before it is introduced
+                //~| WARN this was previously accepted
 #[derive(Empty)]
 struct S {
     #[empty_helper] // OK, no ambiguity, derive helpers have highest priority

src/test/ui/proc-macro/derive-helper-shadowing.stderr

@@ -1,17 +1,17 @@
 error: cannot use a derive helper attribute through an import
-  --> $DIR/derive-helper-shadowing.rs:40:15
+  --> $DIR/derive-helper-shadowing.rs:42:15
    |
 LL |             #[renamed]
    |               ^^^^^^^
    |
 note: the derive helper attribute imported here
-  --> $DIR/derive-helper-shadowing.rs:39:17
+  --> $DIR/derive-helper-shadowing.rs:41:17
    |
 LL |             use empty_helper as renamed;
    |                 ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: cannot find attribute `empty_helper` in this scope
-  --> $DIR/derive-helper-shadowing.rs:36:22
+  --> $DIR/derive-helper-shadowing.rs:38:22
    |
 LL |             #[derive(GenHelperUse)]
    |                      ^^^^^^^^^^^^
@@ -30,13 +30,13 @@ LL |             gen_helper_use!();
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0659]: `empty_helper` is ambiguous (name vs any other name during import resolution)
-  --> $DIR/derive-helper-shadowing.rs:24:13
+  --> $DIR/derive-helper-shadowing.rs:26:13
    |
 LL |         use empty_helper;
    |             ^^^^^^^^^^^^ ambiguous name
    |
 note: `empty_helper` could refer to the derive helper attribute defined here
-  --> $DIR/derive-helper-shadowing.rs:20:10
+  --> $DIR/derive-helper-shadowing.rs:22:10
    |
 LL | #[derive(Empty)]
    |          ^^^^^
@@ -54,7 +54,7 @@ LL | #[empty_helper]
    |   ^^^^^^^^^^^^ ambiguous name
    |
 note: `empty_helper` could refer to the derive helper attribute defined here
-  --> $DIR/derive-helper-shadowing.rs:20:10
+  --> $DIR/derive-helper-shadowing.rs:22:10
    |
 LL | #[derive(Empty)]
    |          ^^^^^
@@ -65,6 +65,19 @@ LL | use test_macros::empty_attr as empty_helper;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: use `crate::empty_helper` to refer to this attribute macro unambiguously
 
-error: aborting due to 5 previous errors
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/derive-helper-shadowing.rs:19:3
+   |
+LL | #[empty_helper]
+   |   ^^^^^^^^^^^^
+...
+LL | #[derive(Empty)]
+   |          ----- the attribute is introduced here
+   |
+   = note: `#[warn(legacy_derive_helpers)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+error: aborting due to 5 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/proc-macro/derive-helper-vs-legacy.rs

@@ -0,0 +1,12 @@
+// check-pass
+// aux-build:test-macros.rs
+
+#[macro_use]
+extern crate test_macros;
+
+#[derive(Empty)]
+#[empty_helper] // OK, this is both derive helper and legacy derive helper
+#[derive(Empty)]
+struct S;
+
+fn main() {}

src/test/ui/proc-macro/derive-multiple-with-packed.rs

@@ -0,0 +1,11 @@
+// check-pass
+
+#[derive(Clone, Copy)]
+#[derive(Debug)] // OK, even if `Copy` is in the different `#[derive]`
+#[derive(PartialEq)] // OK too
+#[repr(packed)]
+struct CacheRecordHeader {
+    field: u64,
+}
+
+fn main() {}

src/test/ui/proc-macro/helper-attr-blocked-by-import-ambig.rs

@@ -4,8 +4,10 @@
 extern crate test_macros;
 use test_macros::empty_attr as empty_helper;
 
-#[derive(Empty)]
 #[empty_helper] //~ ERROR `empty_helper` is ambiguous
+                //~| WARN derive helper attribute is used before it is introduced
+                //~| WARN this was previously accepted
+#[derive(Empty)]
 struct S;
 
 fn main() {}

src/test/ui/proc-macro/helper-attr-blocked-by-import-ambig.stderr

@@ -1,11 +1,11 @@
 error[E0659]: `empty_helper` is ambiguous (derive helper attribute vs any other name)
-  --> $DIR/helper-attr-blocked-by-import-ambig.rs:8:3
+  --> $DIR/helper-attr-blocked-by-import-ambig.rs:7:3
    |
 LL | #[empty_helper]
    |   ^^^^^^^^^^^^ ambiguous name
    |
 note: `empty_helper` could refer to the derive helper attribute defined here
-  --> $DIR/helper-attr-blocked-by-import-ambig.rs:7:10
+  --> $DIR/helper-attr-blocked-by-import-ambig.rs:10:10
    |
 LL | #[derive(Empty)]
    |          ^^^^^
@@ -16,6 +16,19 @@ LL | use test_macros::empty_attr as empty_helper;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: use `crate::empty_helper` to refer to this attribute macro unambiguously
 
-error: aborting due to previous error
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/helper-attr-blocked-by-import-ambig.rs:7:3
+   |
+LL | #[empty_helper]
+   |   ^^^^^^^^^^^^
+...
+LL | #[derive(Empty)]
+   |          ----- the attribute is introduced here
+   |
+   = note: `#[warn(legacy_derive_helpers)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+error: aborting due to previous error; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/proc-macro/issue-75930-derive-cfg.rs

@@ -13,7 +13,8 @@
 #[macro_use]
 extern crate test_macros;
 
-#[print_helper(a)]
+#[print_helper(a)] //~ WARN derive helper attribute is used before it is introduced
+                   //~| WARN this was previously accepted
 #[cfg_attr(not(FALSE), allow(dead_code))]
 #[print_attr]
 #[derive(Print)]

src/test/ui/proc-macro/issue-75930-derive-cfg.stderr

@@ -0,0 +1,15 @@
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/issue-75930-derive-cfg.rs:16:3
+   |
+LL | #[print_helper(a)]
+   |   ^^^^^^^^^^^^
+...
+LL | #[derive(Print)]
+   |          ----- the attribute is introduced here
+   |
+   = note: `#[warn(legacy_derive_helpers)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+warning: 1 warning emitted
+

src/test/ui/proc-macro/proc-macro-attributes.rs

@@ -4,10 +4,18 @@
 extern crate derive_b;
 
 #[B] //~ ERROR `B` is ambiguous
+     //~| WARN derive helper attribute is used before it is introduced
+     //~| WARN this was previously accepted
 #[C] //~ ERROR cannot find attribute `C` in this scope
 #[B(D)] //~ ERROR `B` is ambiguous
+        //~| WARN derive helper attribute is used before it is introduced
+        //~| WARN this was previously accepted
 #[B(E = "foo")] //~ ERROR `B` is ambiguous
+                //~| WARN derive helper attribute is used before it is introduced
+                //~| WARN this was previously accepted
 #[B(arbitrary tokens)] //~ ERROR `B` is ambiguous
+                       //~| WARN derive helper attribute is used before it is introduced
+                       //~| WARN this was previously accepted
 #[derive(B)]
 struct B;
 

src/test/ui/proc-macro/proc-macro-attributes.stderr

@@ -1,5 +1,5 @@
 error: cannot find attribute `C` in this scope
-  --> $DIR/proc-macro-attributes.rs:7:3
+  --> $DIR/proc-macro-attributes.rs:9:3
    |
 LL | #[C]
    |   ^ help: a derive helper attribute with a similar name exists: `B`
@@ -11,41 +11,7 @@ LL | #[B]
    |   ^ ambiguous name
    |
 note: `B` could refer to the derive helper attribute defined here
-  --> $DIR/proc-macro-attributes.rs:11:10
-   |
-LL | #[derive(B)]
-   |          ^
-note: `B` could also refer to the derive macro imported here
-  --> $DIR/proc-macro-attributes.rs:3:1
-   |
-LL | #[macro_use]
-   | ^^^^^^^^^^^^
-
-error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
-  --> $DIR/proc-macro-attributes.rs:8:3
-   |
-LL | #[B(D)]
-   |   ^ ambiguous name
-   |
-note: `B` could refer to the derive helper attribute defined here
-  --> $DIR/proc-macro-attributes.rs:11:10
-   |
-LL | #[derive(B)]
-   |          ^
-note: `B` could also refer to the derive macro imported here
-  --> $DIR/proc-macro-attributes.rs:3:1
-   |
-LL | #[macro_use]
-   | ^^^^^^^^^^^^
-
-error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
-  --> $DIR/proc-macro-attributes.rs:9:3
-   |
-LL | #[B(E = "foo")]
-   |   ^ ambiguous name
-   |
-note: `B` could refer to the derive helper attribute defined here
-  --> $DIR/proc-macro-attributes.rs:11:10
+  --> $DIR/proc-macro-attributes.rs:19:10
    |
 LL | #[derive(B)]
    |          ^
@@ -58,11 +24,11 @@ LL | #[macro_use]
 error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
   --> $DIR/proc-macro-attributes.rs:10:3
    |
-LL | #[B(arbitrary tokens)]
+LL | #[B(D)]
    |   ^ ambiguous name
    |
 note: `B` could refer to the derive helper attribute defined here
-  --> $DIR/proc-macro-attributes.rs:11:10
+  --> $DIR/proc-macro-attributes.rs:19:10
    |
 LL | #[derive(B)]
    |          ^
@@ -72,6 +38,89 @@ note: `B` could also refer to the derive macro imported here
 LL | #[macro_use]
    | ^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
+  --> $DIR/proc-macro-attributes.rs:13:3
+   |
+LL | #[B(E = "foo")]
+   |   ^ ambiguous name
+   |
+note: `B` could refer to the derive helper attribute defined here
+  --> $DIR/proc-macro-attributes.rs:19:10
+   |
+LL | #[derive(B)]
+   |          ^
+note: `B` could also refer to the derive macro imported here
+  --> $DIR/proc-macro-attributes.rs:3:1
+   |
+LL | #[macro_use]
+   | ^^^^^^^^^^^^
+
+error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
+  --> $DIR/proc-macro-attributes.rs:16:3
+   |
+LL | #[B(arbitrary tokens)]
+   |   ^ ambiguous name
+   |
+note: `B` could refer to the derive helper attribute defined here
+  --> $DIR/proc-macro-attributes.rs:19:10
+   |
+LL | #[derive(B)]
+   |          ^
+note: `B` could also refer to the derive macro imported here
+  --> $DIR/proc-macro-attributes.rs:3:1
+   |
+LL | #[macro_use]
+   | ^^^^^^^^^^^^
+
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/proc-macro-attributes.rs:6:3
+   |
+LL | #[B]
+   |   ^
+...
+LL | #[derive(B)]
+   |          - the attribute is introduced here
+   |
+   = note: `#[warn(legacy_derive_helpers)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/proc-macro-attributes.rs:10:3
+   |
+LL | #[B(D)]
+   |   ^
+...
+LL | #[derive(B)]
+   |          - the attribute is introduced here
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/proc-macro-attributes.rs:13:3
+   |
+LL | #[B(E = "foo")]
+   |   ^
+...
+LL | #[derive(B)]
+   |          - the attribute is introduced here
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+warning: derive helper attribute is used before it is introduced
+  --> $DIR/proc-macro-attributes.rs:16:3
+   |
+LL | #[B(arbitrary tokens)]
+   |   ^
+...
+LL | #[derive(B)]
+   |          - the attribute is introduced here
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
+
+error: aborting due to 5 previous errors; 4 warnings emitted
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/proc-macro/reserved-macro-names.rs

@@ -17,9 +17,3 @@ pub fn cfg_attr(_: TokenStream, input: TokenStream) -> TokenStream {
     //~^ ERROR name `cfg_attr` is reserved in attribute namespace
     input
 }
-
-#[proc_macro_attribute]
-pub fn derive(_: TokenStream, input: TokenStream) -> TokenStream {
-    //~^ ERROR name `derive` is reserved in attribute namespace
-    input
-}

src/test/ui/proc-macro/reserved-macro-names.stderr

@@ -10,11 +10,5 @@ error: name `cfg_attr` is reserved in attribute namespace
 LL | pub fn cfg_attr(_: TokenStream, input: TokenStream) -> TokenStream {
    |        ^^^^^^^^
 
-error: name `derive` is reserved in attribute namespace
-  --> $DIR/reserved-macro-names.rs:22:8
-   |
-LL | pub fn derive(_: TokenStream, input: TokenStream) -> TokenStream {
-   |        ^^^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors