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

Author: matthiaskrgr

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)`

compiler/rustc_lint_defs/src/builtin.rs

@@ -156,7 +156,7 @@ declare_lint! {
     ///
     /// ```rust
     /// #![forbid(warnings)]
-    /// #![deny(bad_style)]
+    /// #![warn(bad_style)]
     ///
     /// fn main() {}
     /// ```

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

tests/ui/lint/auxiliary/allow-macro.rs

@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_allow {
+    () => {
+        #[allow(unsafe_code)]
+        let _so_safe = 0;
+    };
+}

tests/ui/lint/auxiliary/deny-macro.rs

@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_deny {
+    () => {
+        #[deny(unsafe_code)]
+        let _so_safe = 0;
+    };
+}

tests/ui/lint/auxiliary/forbid-macro.rs

@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_forbid {
+    () => {
+        #[forbid(unsafe_code)]
+        let _so_safe = 0;
+    };
+}

tests/ui/lint/auxiliary/warn-macro.rs

@@ -0,0 +1,7 @@
+#[macro_export]
+macro_rules! emit_warn {
+    () => {
+        #[warn(unsafe_code)]
+        let _so_safe = 0;
+    };
+}

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`.

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`.

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
+        }
+    }
+}