Make SEMICOLON_IN_EXPRESSIONS_FROM_MACROS warn by default

Author: Aaron1011

compiler/rustc_lint_defs/src/builtin.rs

@@ -2799,7 +2799,7 @@ declare_lint! {
     /// [issue #79813]: https://github.com/rust-lang/rust/issues/79813
     /// [future-incompatible]: ../index.md#future-incompatible-lints
     pub SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
-    Allow,
+    Warn,
     "trailing semicolon in macro body used as expression",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #79813 <https://github.com/rust-lang/rust/issues/79813>",

library/std/src/macros.rs

@@ -290,7 +290,7 @@ macro_rules! dbg {
     // `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
     // will be malformed.
     () => {
-        $crate::eprintln!("[{}:{}]", $crate::file!(), $crate::line!());
+        $crate::eprintln!("[{}:{}]", $crate::file!(), $crate::line!())
     };
     ($val:expr $(,)?) => {
         // Use of `match` here is intentional because it affects the lifetimes

src/test/ui/hygiene/auxiliary/intercrate.rs

@@ -5,7 +5,7 @@ pub mod foo {
     mod bar {
         fn f() -> u32 { 1 }
         pub macro m() {
-            f();
+            f()
         }
     }
 }

src/test/ui/hygiene/hygienic-label-1.rs

@@ -3,5 +3,5 @@ macro_rules! foo {
 }
 
 pub fn main() {
-    'x: loop { foo!() }
+    'x: loop { foo!(); }
 }

src/test/ui/hygiene/hygienic-label-1.stderr

@@ -4,8 +4,8 @@ error[E0426]: use of undeclared label `'x`
 LL |     () => { break 'x; }
    |                   ^^ undeclared label `'x`
 ...
-LL |     'x: loop { foo!() }
-   |                ------ in this macro invocation
+LL |     'x: loop { foo!(); }
+   |                ------- in this macro invocation
    |
    = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/hygiene/hygienic-label-3.rs

@@ -4,6 +4,6 @@ macro_rules! foo {
 
 pub fn main() {
     'x: for _ in 0..1 {
-        foo!()
+        foo!();
     };
 }

src/test/ui/hygiene/hygienic-label-3.stderr

@@ -4,8 +4,8 @@ error[E0426]: use of undeclared label `'x`
 LL |     () => { break 'x; }
    |                   ^^ undeclared label `'x`
 ...
-LL |         foo!()
-   |         ------ in this macro invocation
+LL |         foo!();
+   |         ------- in this macro invocation
    |
    = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/lint/semicolon-in-expressions-from-macros/allow-semicolon-in-expressions-from-macros.rs

@@ -0,0 +1,16 @@
+// check-pass
+// Ensure that trailing semicolons cause warnings by default
+
+macro_rules! foo {
+    () => {
+        true; //~  WARN trailing semicolon in macro
+              //~| WARN this was previously
+    }
+}
+
+fn main() {
+    let _val = match true {
+        true => false,
+        _ => foo!()
+    };
+}

src/test/ui/lint/semicolon-in-expressions-from-macros/warn-semicolon-in-expressions-from-macros.rs

@@ -0,0 +1,16 @@
+warning: trailing semicolon in macro used in expression position
+  --> $DIR/warn-semicolon-in-expressions-from-macros.rs:6:13
+   |
+LL |         true;
+   |             ^
+...
+LL |         _ => foo!()
+   |              ------ in this macro invocation
+   |
+   = note: `#[warn(semicolon_in_expressions_from_macros)]` 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 #79813 <https://github.com/rust-lang/rust/issues/79813>
+   = note: this warning originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: 1 warning emitted
+