Rollup merge of #121560 - Noratrieb:stop-lint-macro-nonsense, r=jieyouxu

Allow `#[deny]` inside `#[forbid]` as a no-op

Forbid cannot be overriden. When someome tries to do this anyways, it results in a hard error. That makes sense.

Except it doesn't, because macros. Macros may reasonably use `#[deny]` (or `#[warn]` for an allow-by-default lint) in their expansion to assert that their expanded code follows the lint. This is doesn't work when the output gets expanded into a `forbid()` context. This is pretty silly, since both the macros and the code agree on the lint!

By making it a warning instead, we remove the problem with the macro, which is now nothing as warnings are suppressed in macro expanded code, while still telling users that something is up.

fixes #121483

18 files changed, 260 insertions, 32 deletions

diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index 89a67fc0d89..95a8e7625ff 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -493,7 +493,10 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         //
         // This means that this only errors if we're truly lowering the lint
         // level from forbid.
-        if self.lint_added_lints && level != Level::Forbid && old_level == Level::Forbid {
+        if self.lint_added_lints && level == Level::Deny && old_level == Level::Forbid {
+            // Having a deny inside a forbid is fine and is ignored, so we skip this check.
+            return;
+        } else if self.lint_added_lints && level != Level::Forbid && old_level == Level::Forbid {
             // Backwards compatibility check:
             //
             // We used to not consider `forbid(lint_group)`
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 45a5ce0ca20..c11571182fe 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -156,7 +156,7 @@ declare_lint! {
     ///
     /// ```rust
     /// #![forbid(warnings)]
-    /// #![deny(bad_style)]
+    /// #![warn(bad_style)]
     ///
     /// fn main() {}
     /// ```
diff --git a/src/tools/tidy/src/issues.txt b/src/tools/tidy/src/issues.txt
index 22126674c15..97c42752c12 100644
--- a/src/tools/tidy/src/issues.txt
+++ b/src/tools/tidy/src/issues.txt
@@ -2758,7 +2758,6 @@ ui/lint/issue-63364.rs
 ui/lint/issue-70819-dont-override-forbid-in-same-scope.rs
 ui/lint/issue-79546-fuel-ice.rs
 ui/lint/issue-79744.rs
-ui/lint/issue-80988.rs
 ui/lint/issue-81218.rs
 ui/lint/issue-83477.rs
 ui/lint/issue-87274-paren-parent.rs
diff --git a/tests/ui/lint/auxiliary/allow-macro.rs b/tests/ui/lint/auxiliary/allow-macro.rs
new file mode 100644
index 00000000000..35980e2e6ac
--- /dev/null
+++ b/tests/ui/lint/auxiliary/allow-macro.rs
@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_allow {
+    () => {
+        #[allow(unsafe_code)]
+        let _so_safe = 0;
+    };
+}
diff --git a/tests/ui/lint/auxiliary/deny-macro.rs b/tests/ui/lint/auxiliary/deny-macro.rs
new file mode 100644
index 00000000000..6106cd0ef17
--- /dev/null
+++ b/tests/ui/lint/auxiliary/deny-macro.rs
@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_deny {
+    () => {
+        #[deny(unsafe_code)]
+        let _so_safe = 0;
+    };
+}
diff --git a/tests/ui/lint/auxiliary/forbid-macro.rs b/tests/ui/lint/auxiliary/forbid-macro.rs
new file mode 100644
index 00000000000..aa74d0cf314
--- /dev/null
+++ b/tests/ui/lint/auxiliary/forbid-macro.rs
@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_forbid {
+    () => {
+        #[forbid(unsafe_code)]
+        let _so_safe = 0;
+    };
+}
diff --git a/tests/ui/lint/auxiliary/warn-macro.rs b/tests/ui/lint/auxiliary/warn-macro.rs
new file mode 100644
index 00000000000..8216b65c74b
--- /dev/null
+++ b/tests/ui/lint/auxiliary/warn-macro.rs
@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_warn {
+    () => {
+        #[warn(unsafe_code)]
+        let _so_safe = 0;
+    };
+}
diff --git a/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid.stderr b/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid.stderr
new file mode 100644
index 00000000000..06086cbef8a
--- /dev/null
+++ b/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid.stderr
@@ -0,0 +1,35 @@
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: usage of an `unsafe` block
+  --> $DIR/deny-inside-forbid-ignored.rs:16:13
+   |
+LL |             unsafe { /* ≽^•⩊•^≼ */ }
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deny-inside-forbid-ignored.rs:8:10
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0453`.
diff --git a/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid_warnings.stderr b/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid_warnings.stderr
new file mode 100644
index 00000000000..06086cbef8a
--- /dev/null
+++ b/tests/ui/lint/deny-inside-forbid-ignored.cli_forbid_warnings.stderr
@@ -0,0 +1,35 @@
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: usage of an `unsafe` block
+  --> $DIR/deny-inside-forbid-ignored.rs:16:13
+   |
+LL |             unsafe { /* ≽^•⩊•^≼ */ }
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deny-inside-forbid-ignored.rs:8:10
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0453`.
diff --git a/tests/ui/lint/deny-inside-forbid-ignored.rs b/tests/ui/lint/deny-inside-forbid-ignored.rs
new file mode 100644
index 00000000000..b14a3e94bb5
--- /dev/null
+++ b/tests/ui/lint/deny-inside-forbid-ignored.rs
@@ -0,0 +1,20 @@
+//! Ensure that using deny inside forbid is treated as a no-op, and does not override the level to
+//! deny.
+
+//@ revisions: source_only cli_forbid cli_forbid_warnings
+//@[cli_forbid] compile-flags: -F unsafe_code
+//@[cli_forbid_warnings] compile-flags: -F warnings
+
+#[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+fn main() {
+    #[deny(unsafe_code)] // m-m-maybe we can have unsafe code in here?
+    {
+        #[allow(unsafe_code)] // let's have some unsafe code in here
+        //~^ ERROR allow(unsafe_code) incompatible with previous forbid
+        //~| ERROR allow(unsafe_code) incompatible with previous forbid
+        {
+            unsafe { /* ≽^•⩊•^≼ */ }
+            //~^ ERROR usage of an `unsafe` block
+        }
+    }
+}
diff --git a/tests/ui/lint/deny-inside-forbid-ignored.source_only.stderr b/tests/ui/lint/deny-inside-forbid-ignored.source_only.stderr
new file mode 100644
index 00000000000..06086cbef8a
--- /dev/null
+++ b/tests/ui/lint/deny-inside-forbid-ignored.source_only.stderr
@@ -0,0 +1,35 @@
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/deny-inside-forbid-ignored.rs:12:17
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ----------- `forbid` level set here
+...
+LL |         #[allow(unsafe_code)] // let's have some unsafe code in here
+   |                 ^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: usage of an `unsafe` block
+  --> $DIR/deny-inside-forbid-ignored.rs:16:13
+   |
+LL |             unsafe { /* ≽^•⩊•^≼ */ }
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deny-inside-forbid-ignored.rs:8:10
+   |
+LL | #[forbid(unsafe_code)] // NO UNSAFE CODE IN HERE!!
+   |          ^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0453`.
diff --git a/tests/ui/lint/forbid-macro-with-deny.allow.stderr b/tests/ui/lint/forbid-macro-with-deny.allow.stderr
new file mode 100644
index 00000000000..77735c1c5d3
--- /dev/null
+++ b/tests/ui/lint/forbid-macro-with-deny.allow.stderr
@@ -0,0 +1,26 @@
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/forbid-macro-with-deny.rs:39:5
+   |
+LL | #![forbid(unsafe_code)]
+   |           ----------- `forbid` level set here
+...
+LL |     allow_macro::emit_allow! {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: this error originates in the macro `allow_macro::emit_allow` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0453]: allow(unsafe_code) incompatible with previous forbid
+  --> $DIR/forbid-macro-with-deny.rs:39:5
+   |
+LL | #![forbid(unsafe_code)]
+   |           ----------- `forbid` level set here
+...
+LL |     allow_macro::emit_allow! {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+   = note: this error originates in the macro `allow_macro::emit_allow` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0453`.
diff --git a/tests/ui/lint/forbid-macro-with-deny.rs b/tests/ui/lint/forbid-macro-with-deny.rs
new file mode 100644
index 00000000000..85f67ea3631
--- /dev/null
+++ b/tests/ui/lint/forbid-macro-with-deny.rs
@@ -0,0 +1,45 @@
+//! Ensure that when a macro (or normal code) does `#[deny]` inside a `#[forbid]` context, no error
+//! is emitted, as both parties agree on the treatment of the lint.
+//!
+//! However, still emit an error if the macro does `#[allow]` or `#[warn]`.
+
+//@ revisions: forbid deny warn allow
+//@[forbid] aux-build:forbid-macro.rs
+//@[deny] aux-build:deny-macro.rs
+//@[warn] aux-build:warn-macro.rs
+//@[allow] aux-build:allow-macro.rs
+
+//@[forbid] check-pass
+//@[deny] check-pass
+
+#![forbid(unsafe_code)]
+
+#[cfg(allow)]
+extern crate allow_macro;
+#[cfg(deny)]
+extern crate deny_macro;
+#[cfg(forbid)]
+extern crate forbid_macro;
+#[cfg(warn)]
+extern crate warn_macro;
+
+fn main() {
+    #[cfg(forbid)]
+    forbid_macro::emit_forbid! {} // OK
+
+    #[cfg(deny)]
+    deny_macro::emit_deny! {} // OK
+
+    #[cfg(warn)]
+    warn_macro::emit_warn! {}
+    //[warn]~^ ERROR warn(unsafe_code) incompatible with previous forbid
+    //[warn]~| ERROR warn(unsafe_code) incompatible with previous forbid
+
+    #[cfg(allow)]
+    allow_macro::emit_allow! {}
+    //[allow]~^ ERROR allow(unsafe_code) incompatible with previous forbid
+    //[allow]~| ERROR allow(unsafe_code) incompatible with previous forbid
+
+    #[deny(unsafe_code)] // OK
+    let _ = 0;
+}
diff --git a/tests/ui/lint/forbid-macro-with-deny.warn.stderr b/tests/ui/lint/forbid-macro-with-deny.warn.stderr
new file mode 100644
index 00000000000..10452ebd1b6
--- /dev/null
+++ b/tests/ui/lint/forbid-macro-with-deny.warn.stderr
@@ -0,0 +1,26 @@
+error[E0453]: warn(unsafe_code) incompatible with previous forbid
+  --> $DIR/forbid-macro-with-deny.rs:34:5
+   |
+LL | #![forbid(unsafe_code)]
+   |           ----------- `forbid` level set here
+...
+LL |     warn_macro::emit_warn! {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: this error originates in the macro `warn_macro::emit_warn` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0453]: warn(unsafe_code) incompatible with previous forbid
+  --> $DIR/forbid-macro-with-deny.rs:34:5
+   |
+LL | #![forbid(unsafe_code)]
+   |           ----------- `forbid` level set here
+...
+LL |     warn_macro::emit_warn! {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ overruled by previous forbid
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+   = note: this error originates in the macro `warn_macro::emit_warn` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0453`.
diff --git a/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.rs b/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.rs
index 37d96129317..45b78d75b27 100644
--- a/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.rs
+++ b/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.rs
@@ -19,9 +19,9 @@
 fn forbid_first(num: i32) -> i32 {
     #![forbid(unused)]
     #![deny(unused)]
-    //~^ ERROR: deny(unused) incompatible with previous forbid
-    //~| WARNING being phased out
     #![warn(unused)]
+    //~^ ERROR: warn(unused) incompatible with previous forbid
+    //~| WARNING being phased out
     #![allow(unused)]
 
     num * num
diff --git a/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.stderr b/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.stderr
index f78bf899b84..407eaf1c60a 100644
--- a/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.stderr
+++ b/tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.stderr
@@ -1,9 +1,10 @@
-error: deny(unused) incompatible with previous forbid
-  --> $DIR/issue-70819-dont-override-forbid-in-same-scope.rs:21:13
+error: warn(unused) incompatible with previous forbid
+  --> $DIR/issue-70819-dont-override-forbid-in-same-scope.rs:22:13
    |
 LL |     #![forbid(unused)]
    |               ------ `forbid` level set here
 LL |     #![deny(unused)]
+LL |     #![warn(unused)]
    |             ^^^^^^ overruled by previous forbid
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
diff --git a/tests/ui/lint/issue-80988.rs b/tests/ui/lint/issue-80988.rs
deleted file mode 100644
index 80decd8e736..00000000000
--- a/tests/ui/lint/issue-80988.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-// Regression test for #80988
-//
-//@ check-pass
-
-#![forbid(warnings)]
-
-#[deny(warnings)]
-//~^ WARNING incompatible with previous forbid
-//~| WARNING being phased out
-fn main() {}
diff --git a/tests/ui/lint/issue-80988.stderr b/tests/ui/lint/issue-80988.stderr
deleted file mode 100644
index afc93fcfeef..00000000000
--- a/tests/ui/lint/issue-80988.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-warning: deny(warnings) incompatible with previous forbid
-  --> $DIR/issue-80988.rs:7:8
-   |
-LL | #![forbid(warnings)]
-   |           -------- `forbid` level set here
-LL |
-LL | #[deny(warnings)]
-   |        ^^^^^^^^ overruled by previous forbid
-   |
-   = 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 #81670 <https://github.com/rust-lang/rust/issues/81670>
-   = note: `#[warn(forbidden_lint_groups)]` on by default
-
-warning: 1 warning emitted
-