Rollup merge of #83127 - Aaron1011:time-macros-impl-warn, r=petrochenkov

Introduce `proc_macro_back_compat` lint, and emit for `time-macros-impl`

Now that future-incompat-report support has landed in nightly Cargo, we
can start to make progress towards removing the various proc-macro
back-compat hacks that have accumulated in the compiler.

This PR introduces a new lint `proc_macro_back_compat`, which results in
a future-incompat-report entry being generated. All proc-macro
back-compat warnings will be grouped under this lint. Note that this
lint will never actually become a hard error - instead, we will remove
the special cases for various macros, which will cause older versions of
those crates to emit some other error.

I've added code to fire this lint for the `time-macros-impl` case. This
is the easiest case out of all of our current back-compat hacks - the
crate was renamed to `time-macros`, so seeing a filename with
`time-macros-impl` guarantees that an older version of the parent `time`
crate is in use.

When Cargo's future-incompat-report feature gets stabilized, affected
users will start to see future-incompat warnings when they build their
crates.

3 files changed, 83 insertions, 11 deletions

diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
index 652fabf34ac..7f3f5e36f50 100644
--- a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
@@ -24,7 +24,8 @@ mod no_version {
     }
 
     struct Foo;
-    impl_macros!(Foo);
+    impl_macros!(Foo); //~ WARN  using an old version
+                       //~| WARN this was previously
     arrays!(Foo);
     other!(Foo);
 }
@@ -40,7 +41,8 @@ mod with_version {
     }
 
     struct Foo;
-    impl_macros!(Foo);
+    impl_macros!(Foo); //~  WARN using an old version
+                       //~| WARN this was previously
     arrays!(Foo);
     other!(Foo);
 }
diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr
new file mode 100644
index 00000000000..9370440a635
--- /dev/null
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr
@@ -0,0 +1,70 @@
+warning: using an old version of `time-macros-impl`
+  --> $DIR/time-macros-impl/src/lib.rs:5:32
+   |
+LL |         #[my_macro] struct One($name);
+   |                                ^^^^^
+   | 
+  ::: $DIR/group-compat-hack.rs:27:5
+   |
+LL |     impl_macros!(Foo);
+   |     ------------------ in this macro invocation
+   |
+   = note: `#[warn(proc_macro_back_compat)]` 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 #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: using an old version of `time-macros-impl`
+  --> $DIR/time-macros-impl-0.1.0/src/lib.rs:5:32
+   |
+LL |         #[my_macro] struct One($name);
+   |                                ^^^^^
+   | 
+  ::: $DIR/group-compat-hack.rs:44:5
+   |
+LL |     impl_macros!(Foo);
+   |     ------------------ in this macro invocation
+   |
+   = 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 #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: 2 warnings emitted
+
+Future incompatibility report: Future breakage date: None, diagnostic:
+warning: using an old version of `time-macros-impl`
+  --> $DIR/time-macros-impl/src/lib.rs:5:32
+   |
+LL |         #[my_macro] struct One($name);
+   |                                ^^^^^
+   | 
+  ::: $DIR/group-compat-hack.rs:27:5
+   |
+LL |     impl_macros!(Foo);
+   |     ------------------ in this macro invocation
+   |
+   = note: `#[warn(proc_macro_back_compat)]` 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 #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+Future breakage date: None, diagnostic:
+warning: using an old version of `time-macros-impl`
+  --> $DIR/time-macros-impl-0.1.0/src/lib.rs:5:32
+   |
+LL |         #[my_macro] struct One($name);
+   |                                ^^^^^
+   | 
+  ::: $DIR/group-compat-hack.rs:44:5
+   |
+LL |     impl_macros!(Foo);
+   |     ------------------ in this macro invocation
+   |
+   = 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 #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
index c6b18ab674b..468cb511915 100644
--- a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
@@ -1,10 +1,10 @@
 Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/time-macros-impl/src/lib.rs:5:21: 5:27 (#6) }, Ident { ident: "One", span: $DIR/time-macros-impl/src/lib.rs:5:28: 5:31 (#6) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:27:18: 27:21 (#0) }], span: $DIR/time-macros-impl/src/lib.rs:5:31: 5:38 (#6) }, Punct { ch: ';', spacing: Alone, span: $DIR/time-macros-impl/src/lib.rs:5:38: 5:39 (#6) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/js-sys/src/lib.rs:5:21: 5:27 (#10) }, Ident { ident: "Two", span: $DIR/js-sys/src/lib.rs:5:28: 5:31 (#10) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:28:13: 28:16 (#0) }], span: $DIR/js-sys/src/lib.rs:5:31: 5:38 (#10) }, Punct { ch: ';', spacing: Alone, span: $DIR/js-sys/src/lib.rs:5:38: 5:39 (#10) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/group-compat-hack.rs:22:25: 22:31 (#14) }, Ident { ident: "Three", span: $DIR/group-compat-hack.rs:22:32: 22:37 (#14) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:29:12: 29:15 (#0) }], span: $DIR/group-compat-hack.rs:22:38: 22:43 (#14) }], span: $DIR/group-compat-hack.rs:22:37: 22:44 (#14) }, Punct { ch: ';', spacing: Alone, span: $DIR/group-compat-hack.rs:22:44: 22:45 (#14) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:21: 5:27 (#20) }, Ident { ident: "One", span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:28: 5:31 (#20) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:43:18: 43:21 (#0) }], span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:31: 5:38 (#20) }, Punct { ch: ';', spacing: Alone, span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:38: 5:39 (#20) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/js-sys-0.3.17/src/lib.rs:5:21: 5:27 (#24) }, Ident { ident: "Two", span: $DIR/js-sys-0.3.17/src/lib.rs:5:28: 5:31 (#24) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:44:13: 44:16 (#0) }], span: $DIR/js-sys-0.3.17/src/lib.rs:5:31: 5:38 (#24) }, Punct { ch: ';', spacing: Alone, span: $DIR/js-sys-0.3.17/src/lib.rs:5:38: 5:39 (#24) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/group-compat-hack.rs:38:25: 38:31 (#28) }, Ident { ident: "Three", span: $DIR/group-compat-hack.rs:38:32: 38:37 (#28) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:45:12: 45:15 (#0) }], span: $DIR/group-compat-hack.rs:38:38: 38:43 (#28) }], span: $DIR/group-compat-hack.rs:38:37: 38:44 (#28) }, Punct { ch: ';', spacing: Alone, span: $DIR/group-compat-hack.rs:38:44: 38:45 (#28) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web/src/extract.rs:5:21: 5:27 (#33) }, Ident { ident: "Three", span: $DIR/actix-web/src/extract.rs:5:28: 5:33 (#33) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:52:21: 52:24 (#0) }], span: $DIR/actix-web/src/extract.rs:5:33: 5:37 (#33) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web/src/extract.rs:5:37: 5:38 (#33) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web-2.0.0/src/extract.rs:5:21: 5:27 (#38) }, Ident { ident: "Three", span: $DIR/actix-web-2.0.0/src/extract.rs:5:28: 5:33 (#38) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:59:21: 59:24 (#0) }], span: $DIR/actix-web-2.0.0/src/extract.rs:5:33: 5:37 (#38) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web-2.0.0/src/extract.rs:5:37: 5:38 (#38) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web/src/extract.rs:5:21: 5:27 (#43) }, Ident { ident: "Four", span: $DIR/actori-web/src/extract.rs:5:28: 5:32 (#43) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:66:21: 66:24 (#0) }], span: $DIR/actori-web/src/extract.rs:5:32: 5:36 (#43) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web/src/extract.rs:5:36: 5:37 (#43) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web-2.0.0/src/extract.rs:5:21: 5:27 (#48) }, Ident { ident: "Four", span: $DIR/actori-web-2.0.0/src/extract.rs:5:28: 5:32 (#48) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:73:21: 73:24 (#0) }], span: $DIR/actori-web-2.0.0/src/extract.rs:5:32: 5:36 (#48) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web-2.0.0/src/extract.rs:5:36: 5:37 (#48) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/js-sys/src/lib.rs:5:21: 5:27 (#10) }, Ident { ident: "Two", span: $DIR/js-sys/src/lib.rs:5:28: 5:31 (#10) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:29:13: 29:16 (#0) }], span: $DIR/js-sys/src/lib.rs:5:31: 5:38 (#10) }, Punct { ch: ';', spacing: Alone, span: $DIR/js-sys/src/lib.rs:5:38: 5:39 (#10) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/group-compat-hack.rs:22:25: 22:31 (#14) }, Ident { ident: "Three", span: $DIR/group-compat-hack.rs:22:32: 22:37 (#14) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:30:12: 30:15 (#0) }], span: $DIR/group-compat-hack.rs:22:38: 22:43 (#14) }], span: $DIR/group-compat-hack.rs:22:37: 22:44 (#14) }, Punct { ch: ';', spacing: Alone, span: $DIR/group-compat-hack.rs:22:44: 22:45 (#14) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:21: 5:27 (#20) }, Ident { ident: "One", span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:28: 5:31 (#20) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:44:18: 44:21 (#0) }], span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:31: 5:38 (#20) }, Punct { ch: ';', spacing: Alone, span: $DIR/time-macros-impl-0.1.0/src/lib.rs:5:38: 5:39 (#20) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/js-sys-0.3.17/src/lib.rs:5:21: 5:27 (#24) }, Ident { ident: "Two", span: $DIR/js-sys-0.3.17/src/lib.rs:5:28: 5:31 (#24) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:46:13: 46:16 (#0) }], span: $DIR/js-sys-0.3.17/src/lib.rs:5:31: 5:38 (#24) }, Punct { ch: ';', spacing: Alone, span: $DIR/js-sys-0.3.17/src/lib.rs:5:38: 5:39 (#24) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/group-compat-hack.rs:39:25: 39:31 (#28) }, Ident { ident: "Three", span: $DIR/group-compat-hack.rs:39:32: 39:37 (#28) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:47:12: 47:15 (#0) }], span: $DIR/group-compat-hack.rs:39:38: 39:43 (#28) }], span: $DIR/group-compat-hack.rs:39:37: 39:44 (#28) }, Punct { ch: ';', spacing: Alone, span: $DIR/group-compat-hack.rs:39:44: 39:45 (#28) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web/src/extract.rs:5:21: 5:27 (#33) }, Ident { ident: "Three", span: $DIR/actix-web/src/extract.rs:5:28: 5:33 (#33) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:54:21: 54:24 (#0) }], span: $DIR/actix-web/src/extract.rs:5:33: 5:37 (#33) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web/src/extract.rs:5:37: 5:38 (#33) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web-2.0.0/src/extract.rs:5:21: 5:27 (#38) }, Ident { ident: "Three", span: $DIR/actix-web-2.0.0/src/extract.rs:5:28: 5:33 (#38) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:61:21: 61:24 (#0) }], span: $DIR/actix-web-2.0.0/src/extract.rs:5:33: 5:37 (#38) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web-2.0.0/src/extract.rs:5:37: 5:38 (#38) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web/src/extract.rs:5:21: 5:27 (#43) }, Ident { ident: "Four", span: $DIR/actori-web/src/extract.rs:5:28: 5:32 (#43) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:68:21: 68:24 (#0) }], span: $DIR/actori-web/src/extract.rs:5:32: 5:36 (#43) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web/src/extract.rs:5:36: 5:37 (#43) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web-2.0.0/src/extract.rs:5:21: 5:27 (#48) }, Ident { ident: "Four", span: $DIR/actori-web-2.0.0/src/extract.rs:5:28: 5:32 (#48) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:75:21: 75:24 (#0) }], span: $DIR/actori-web-2.0.0/src/extract.rs:5:32: 5:36 (#48) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web-2.0.0/src/extract.rs:5:36: 5:37 (#48) }]