Make all proc-macro back-compat lints deny-by-default

The affected crates have had plenty of time to update.
By keeping these as lints rather than making them hard errors,
we ensure that downstream crates will still be able to compile,
even if they transitive depend on broken versions of the affected
crates.

This should hopefully discourage anyone from writing any
new code which relies on the backwards-compatibility behavior.

compiler/rustc_lint_defs/src/builtin.rs

@@ -1957,7 +1957,7 @@ declare_lint! {
     /// [issue #50504]: https://github.com/rust-lang/rust/issues/50504
     /// [future-incompatible]: ../index.md#future-incompatible-lints
     pub PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
-    Warn,
+    Deny,
     "detects proc macro derives using inaccessible names from parent modules",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #83583 <https://github.com/rust-lang/rust/issues/83583>",
@@ -3253,7 +3253,7 @@ declare_lint! {
     /// [issue #83125]: https://github.com/rust-lang/rust/issues/83125
     /// [future-incompatible]: ../index.md#future-incompatible-lints
     pub PROC_MACRO_BACK_COMPAT,
-    Warn,
+    Deny,
     "detects usage of old versions of certain proc-macro crates",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #83125 <https://github.com/rust-lang/rust/issues/83125>",

src/test/ui/proc-macro/generate-mod.rs

@@ -13,15 +13,15 @@ generate_mod::check!(); //~ ERROR cannot find type `FromOutside` in this scope
                             //~| ERROR cannot find type `OuterAttr` in this scope
 struct S;
 
-#[derive(generate_mod::CheckDerive)] //~ WARN cannot find type `FromOutside` in this scope
-                                     //~| WARN cannot find type `OuterDerive` in this scope
+#[derive(generate_mod::CheckDerive)] //~ ERROR cannot find type `FromOutside` in this scope
+                                     //~| ERROR cannot find type `OuterDerive` in this scope
                                      //~| WARN this was previously accepted
                                      //~| WARN this was previously accepted
 struct Z;
 
 fn inner_block() {
-    #[derive(generate_mod::CheckDerive)] //~ WARN cannot find type `FromOutside` in this scope
-                                        //~| WARN cannot find type `OuterDerive` in this scope
+    #[derive(generate_mod::CheckDerive)] //~ ERROR cannot find type `FromOutside` in this scope
+                                        //~| ERROR cannot find type `OuterDerive` in this scope
                                         //~| WARN this was previously accepted
                                         //~| WARN this was previously accepted
     struct InnerZ;

src/test/ui/proc-macro/generate-mod.stderr

@@ -38,94 +38,94 @@ LL | #[generate_mod::check_attr]
            OuterAttr
    = note: this error originates in the attribute macro `generate_mod::check_attr` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: cannot find type `FromOutside` in this scope
+error: cannot find type `FromOutside` in this scope
   --> $DIR/generate-mod.rs:16:10
    |
 LL | #[derive(generate_mod::CheckDerive)]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
-   = note: `#[warn(proc_macro_derive_resolution_fallback)]` on by default
+   = note: `#[deny(proc_macro_derive_resolution_fallback)]` 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: cannot find type `OuterDerive` in this scope
+error: cannot find type `OuterDerive` in this scope
   --> $DIR/generate-mod.rs:16:10
    |
 LL | #[derive(generate_mod::CheckDerive)]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: cannot find type `FromOutside` in this scope
+error: cannot find type `FromOutside` in this scope
   --> $DIR/generate-mod.rs:23:14
    |
 LL |     #[derive(generate_mod::CheckDerive)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: cannot find type `OuterDerive` in this scope
+error: cannot find type `OuterDerive` in this scope
   --> $DIR/generate-mod.rs:23:14
    |
 LL |     #[derive(generate_mod::CheckDerive)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 4 previous errors; 4 warnings emitted
+error: aborting due to 8 previous errors
 
 For more information about this error, try `rustc --explain E0412`.
 Future incompatibility report: Future breakage diagnostic:
-warning: cannot find type `FromOutside` in this scope
+error: cannot find type `FromOutside` in this scope
   --> $DIR/generate-mod.rs:16:10
    |
 LL | #[derive(generate_mod::CheckDerive)]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
-   = note: `#[warn(proc_macro_derive_resolution_fallback)]` on by default
+   = note: `#[deny(proc_macro_derive_resolution_fallback)]` 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
-warning: cannot find type `OuterDerive` in this scope
+error: cannot find type `OuterDerive` in this scope
   --> $DIR/generate-mod.rs:16:10
    |
 LL | #[derive(generate_mod::CheckDerive)]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
-warning: cannot find type `FromOutside` in this scope
+error: cannot find type `FromOutside` in this scope
   --> $DIR/generate-mod.rs:23:14
    |
 LL |     #[derive(generate_mod::CheckDerive)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
-warning: cannot find type `OuterDerive` in this scope
+error: cannot find type `OuterDerive` in this scope
   --> $DIR/generate-mod.rs:23:14
    |
 LL |     #[derive(generate_mod::CheckDerive)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^ names from parent modules are not accessible without an explicit import
    |
    = 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 #83583 <https://github.com/rust-lang/rust/issues/83583>
-   = note: this warning originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the derive macro `generate_mod::CheckDerive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 Future breakage diagnostic:
 warning: cannot find type `FromOutside` in this scope

src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs

@@ -1,4 +1,3 @@
-// check-pass
 // aux-build:pin-project-internal-0.4.0.rs
 // compile-flags: -Z span-debug
 
@@ -24,7 +23,7 @@ mod no_version {
     }
 
     struct Foo;
-    impl_macros!(Foo); //~ WARN  using an old version
+    impl_macros!(Foo); //~ ERROR  using an old version
                        //~| WARN this was previously
     arrays!(Foo);
     other!(Foo);
@@ -41,9 +40,9 @@ mod with_version {
     }
 
     struct Foo;
-    impl_macros!(Foo); //~  WARN using an old version
+    impl_macros!(Foo); //~  ERROR using an old version
                        //~| WARN this was previously
-    arrays!(Foo); //~  WARN using an old version
+    arrays!(Foo); //~  ERROR using an old version
                   //~| WARN this was previously
     other!(Foo);
 }
@@ -52,15 +51,15 @@ mod actix_web_test {
     include!("actix-web/src/extract.rs");
 
     struct Foo;
-    tuple_from_req!(Foo); //~ WARN using an old version
+    tuple_from_req!(Foo); //~ ERROR using an old version
     //~| WARN this was previously
 }
 
 mod actix_web_version_test {
     include!("actix-web-2.0.0/src/extract.rs");
 
     struct Foo;
-    tuple_from_req!(Foo); //~ WARN using an old version
+    tuple_from_req!(Foo); //~ ERROR using an old version
     //~| WARN this was previously
 }