Auto merge of #156772 - cuviper:beta-next, r=cuviper

[beta] Revert tearing changes to dbg! (#156589)

This is a straight cherry-pick of the beta-approved #156589.

Author: bors

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -588,6 +588,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     // for dbg!(x) which may take ownership, suggest dbg!(&x) instead
+    // but here we actually do not check whether the macro name is `dbg!`
+    // so that we may extend the scope a bit larger to cover more cases
     fn suggest_ref_for_dbg_args(
         &self,
         body: &hir::Expr<'_>,
@@ -601,41 +603,29 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         });
         let Some(var_info) = var_info else { return };
         let arg_name = var_info.name;
-        struct MatchArgFinder<'tcx> {
-            tcx: TyCtxt<'tcx>,
-            move_span: Span,
+        struct MatchArgFinder {
+            expr_span: Span,
+            match_arg_span: Option<Span>,
             arg_name: Symbol,
-            match_arg_span: Option<Span> = None,
         }
-        impl Visitor<'_> for MatchArgFinder<'_> {
+        impl Visitor<'_> for MatchArgFinder {
             fn visit_expr(&mut self, e: &hir::Expr<'_>) {
                 // dbg! is expanded into a match pattern, we need to find the right argument span
-                if let hir::ExprKind::Match(scrutinee, ..) = &e.kind
-                    && let hir::ExprKind::Tup(args) = scrutinee.kind
-                    && e.span.macro_backtrace().any(|expn| {
-                        expn.macro_def_id.is_some_and(|macro_def_id| {
-                            self.tcx.is_diagnostic_item(sym::dbg_macro, macro_def_id)
-                        })
-                    })
+                if let hir::ExprKind::Match(expr, ..) = &e.kind
+                    && let hir::ExprKind::Path(hir::QPath::Resolved(
+                        _,
+                        path @ Path { segments: [seg], .. },
+                    )) = &expr.kind
+                    && seg.ident.name == self.arg_name
+                    && self.expr_span.source_callsite().contains(expr.span)
                 {
-                    for arg in args {
-                        if let hir::ExprKind::Path(hir::QPath::Resolved(
-                            _,
-                            path @ Path { segments: [seg], .. },
-                        )) = &arg.kind
-                            && seg.ident.name == self.arg_name
-                            && self.move_span.source_equal(arg.span)
-                        {
-                            self.match_arg_span = Some(path.span);
-                            return;
-                        }
-                    }
+                    self.match_arg_span = Some(path.span);
                 }
                 hir::intravisit::walk_expr(self, e);
             }
         }
 
-        let mut finder = MatchArgFinder { tcx: self.infcx.tcx, move_span, arg_name, .. };
+        let mut finder = MatchArgFinder { expr_span: move_span, match_arg_span: None, arg_name };
         finder.visit_expr(body);
         if let Some(macro_arg_span) = finder.match_arg_span {
             err.span_suggestion_verbose(

compiler/rustc_span/src/symbol.rs

@@ -748,7 +748,6 @@ symbols! {
         custom_mir,
         custom_test_frameworks,
         d32,
-        dbg_macro,
         dead_code,
         dealloc,
         debug,

library/std/src/lib.rs

@@ -255,7 +255,10 @@
 #![allow(unused_features)]
 //
 // Features:
-#![cfg_attr(test, feature(internal_output_capture, print_internals, update_panic_count, rt))]
+#![cfg_attr(
+    test,
+    feature(internal_output_capture, print_internals, super_let, update_panic_count, rt)
+)]
 #![cfg_attr(
     all(target_vendor = "fortanix", target_env = "sgx"),
     feature(slice_index_methods, coerce_unsized, sgx_platform)
@@ -471,9 +474,7 @@ extern crate std as realstd;
 
 // The standard macros that are not built-in to the compiler.
 #[macro_use]
-#[doc(hidden)]
-#[unstable(feature = "std_internals", issue = "none")]
-pub mod macros;
+mod macros;
 
 // The runtime entry point and a few unstable public functions used by the
 // compiler

library/std/src/macros.rs

@@ -350,76 +350,37 @@ macro_rules! eprintln {
 /// [`debug!`]: https://docs.rs/log/*/log/macro.debug.html
 /// [`log`]: https://crates.io/crates/log
 #[macro_export]
-#[allow_internal_unstable(std_internals)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "dbg_macro")]
 #[stable(feature = "dbg_macro", since = "1.32.0")]
 macro_rules! dbg {
+    // NOTE: We cannot use `concat!` to make a static string as a format argument
+    // of `eprintln!` because `file!` could contain a `{` or
+    // `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
+    // will be malformed.
     () => {
         $crate::eprintln!("[{}:{}:{}]", $crate::file!(), $crate::line!(), $crate::column!())
     };
-    ($($val:expr),+ $(,)?) => {
-        $crate::macros::dbg_internal!(() () ($($val),+))
-    };
-}
-
-/// Internal macro that processes a list of expressions, binds their results
-/// with `match`, calls `eprint!` with the collected information, and returns
-/// all the evaluated expressions in a tuple.
-///
-/// E.g. `dbg_internal!(() () (1, 2))` expands into
-/// ```rust, ignore
-/// match (1, 2) {
-///     args => {
-///         let (tmp_1, tmp_2) = args;
-///         eprint!("...", &tmp_1, &tmp_2, /* some other arguments */);
-///         (tmp_1, tmp_2)
-///     }
-/// }
-/// ```
-///
-/// This is necessary so that `dbg!` outputs don't get torn, see #136703.
-#[doc(hidden)]
-#[rustc_macro_transparency = "semiopaque"]
-pub macro dbg_internal {
-    (($($piece:literal),+) ($($processed:expr => $bound:ident),+) ()) => {
+    ($val:expr $(,)?) => {
         // Use of `match` here is intentional because it affects the lifetimes
         // of temporaries - https://stackoverflow.com/a/48732525/1063961
-        // Always put the arguments in a tuple to avoid an unused parens lint on the pattern.
-        match ($($processed,)+) {
-            // Move the entire tuple so it doesn't stick around as a temporary (#154988).
-            args => {
-                let ($($bound,)+) = args;
-                $crate::eprint!(
-                    $crate::concat!($($piece),+),
-                    $(
-                        $crate::stringify!($processed),
-                        // The `&T: Debug` check happens here (not in the format literal desugaring)
-                        // to avoid format literal related messages and suggestions.
-                        &&$bound as &dyn $crate::fmt::Debug
-                    ),+,
-                    // The location returned here is that of the macro invocation, so
-                    // it will be the same for all expressions. Thus, label these
-                    // arguments so that they can be reused in every piece of the
-                    // formatting template.
-                    file=$crate::file!(),
-                    line=$crate::line!(),
-                    column=$crate::column!()
+        match $val {
+            tmp => {
+                $crate::eprintln!("[{}:{}:{}] {} = {:#?}",
+                    $crate::file!(),
+                    $crate::line!(),
+                    $crate::column!(),
+                    $crate::stringify!($val),
+                    // The `&T: Debug` check happens here (not in the format literal desugaring)
+                    // to avoid format literal related messages and suggestions.
+                    &&tmp as &dyn $crate::fmt::Debug,
                 );
-                // Comma separate the variables only when necessary so that this will
-                // not yield a tuple for a single expression, but rather just parenthesize
-                // the expression.
-                ($($bound),+)
-
+                tmp
             }
         }
-    },
-    (($($piece:literal),*) ($($processed:expr => $bound:ident),*) ($val:expr $(,$rest:expr)*)) => {
-        $crate::macros::dbg_internal!(
-            ($($piece,)* "[{file}:{line}:{column}] {} = {:#?}\n")
-            ($($processed => $bound,)* $val => tmp)
-            ($($rest),*)
-        )
-    },
+    };
+    ($($val:expr),+ $(,)?) => {
+        ($($crate::dbg!($val)),+,)
+    };
 }
 
 #[doc(hidden)]

library/std/src/macros/tests.rs

@@ -35,3 +35,33 @@ fn no_leaking_internal_temps_from_dbg() {
     // is dropped, then `foo`, then any temporaries left over from `dbg!` are dropped, if present.
     (drop(dbg!(bar)), drop(foo));
 }
+
+/// Test for <https://github.com/rust-lang/rust/issues/155902>:
+/// `dbg!` shouldn't create a temporary that borrowck thinks can live past its invocation on a false
+/// unwind path.
+#[test]
+fn no_leaking_internal_temps_from_dbg_even_on_false_unwind() {
+    #[derive(Debug)]
+    struct Foo;
+    impl Drop for Foo {
+        fn drop(&mut self) {}
+    }
+
+    #[derive(Debug)]
+    struct Bar<'a>(#[allow(unused)] &'a Foo);
+    impl Drop for Bar<'_> {
+        fn drop(&mut self) {}
+    }
+
+    {
+        let foo = Foo;
+        let bar = Bar(&foo);
+        // The temporaries of this `super let`'s scrutinee will outlive `bar` and `foo`, emulating
+        // the drop order of block tail expressions before Rust 2024. If borrowck thinks that a
+        // panic from moving `bar` is possible and that a `Bar<'_>`-containing temporary lives past
+        // the end of the block because of that, this will fail to compile. Because `Foo` implements
+        // `Drop`, it's an error for `foo` to be dropped before such a temporary when unwinding;
+        // otherwise, `foo` would just live to the end of the stack frame when unwinding.
+        super let _ = drop(dbg!(bar));
+    }
+}

src/tools/clippy/clippy_lints/src/dbg_macro.rs

@@ -92,26 +92,33 @@ impl LateLintPass<'_> for DbgMacro {
                                 (macro_call.span, String::from("()"))
                             }
                         },
-                        ExprKind::Match(args, _, _) => {
-                            let suggestion = match args.kind {
-                                // dbg!(1) => 1
-                                ExprKind::Tup([val]) => {
-                                    snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability)
-                                        .to_string()
+                        // dbg!(1)
+                        ExprKind::Match(val, ..) => (
+                            macro_call.span,
+                            snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability)
+                                .to_string(),
+                        ),
+                        // dbg!(2, 3)
+                        ExprKind::Tup(
+                            [
+                                Expr {
+                                    kind: ExprKind::Match(first, ..),
+                                    ..
                                 },
-                                // dbg!(2, 3) => (2, 3)
-                                ExprKind::Tup([first, .., last]) => {
-                                    let snippet = snippet_with_applicability(
-                                        cx,
-                                        first.span.source_callsite().to(last.span.source_callsite()),
-                                        "..",
-                                        &mut applicability,
-                                    );
-                                    format!("({snippet})")
+                                ..,
+                                Expr {
+                                    kind: ExprKind::Match(last, ..),
+                                    ..
                                 },
-                                _ => unreachable!(),
-                            };
-                            (macro_call.span, suggestion)
+                            ],
+                        ) => {
+                            let snippet = snippet_with_applicability(
+                                cx,
+                                first.span.source_callsite().to(last.span.source_callsite()),
+                                "..",
+                                &mut applicability,
+                            );
+                            (macro_call.span, format!("({snippet})"))
                         },
                         _ => unreachable!(),
                     };

src/tools/clippy/clippy_utils/src/sym.rs

@@ -201,6 +201,7 @@ generate! {
     cx,
     cycle,
     cyclomatic_complexity,
+    dbg_macro,
     de,
     debug_struct,
     deprecated_in_future,

src/tools/miri/tests/fail/dangling_pointers/dangling_primitive.stderr

@@ -2,7 +2,7 @@ error: Undefined Behavior: memory access failed: ALLOC has been freed, so this p
   --> tests/fail/dangling_pointers/dangling_primitive.rs:LL:CC
    |
 LL |         dbg!(*ptr);
-   |              ^^^^ Undefined Behavior occurred here
+   |         ^^^^^^^^^^ Undefined Behavior occurred here
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information

src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr

@@ -7,7 +7,7 @@ error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is unin
   --> tests/fail/function_calls/return_pointer_on_unwind.rs:LL:CC
    |
 LL |     dbg!(x.0);
-   |          ^^^ Undefined Behavior occurred here
+   |     ^^^^^^^^^ Undefined Behavior occurred here
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information

tests/ui/borrowck/dbg-issue-120327.rs

@@ -1,44 +1,67 @@
-//! Diagnostic test for <https://github.com/rust-lang/rust/issues/120327>: suggest borrowing
-//! variables passed to `dbg!` that are later used.
-//@ dont-require-annotations: HELP
-
 fn s() -> String {
     let a = String::new();
-    dbg!(a); //~ HELP consider borrowing instead of transferring ownership
+    dbg!(a);
     return a; //~ ERROR use of moved value:
 }
 
 fn m() -> String {
     let a = String::new();
-    dbg!(1, 2, a, 1, 2); //~ HELP consider borrowing instead of transferring ownership
+    dbg!(1, 2, a, 1, 2);
     return a; //~ ERROR use of moved value:
 }
 
 fn t(a: String) -> String {
     let b: String = "".to_string();
-    dbg!(a, b); //~ HELP consider borrowing instead of transferring ownership
+    dbg!(a, b);
     return b; //~ ERROR use of moved value:
 }
 
 fn x(a: String) -> String {
     let b: String = "".to_string();
-    dbg!(a, b); //~ HELP consider borrowing instead of transferring ownership
+    dbg!(a, b);
     return a; //~ ERROR use of moved value:
 }
 
-fn two_of_them(a: String) -> String {
-    dbg!(a, a); //~ ERROR use of moved value
-    //~| HELP consider borrowing instead of transferring ownership
-    //~| HELP consider borrowing instead of transferring ownership
-    return a; //~ ERROR use of moved value
+macro_rules! my_dbg {
+    () => {
+        eprintln!("[{}:{}:{}]", file!(), line!(), column!())
+    };
+    ($val:expr $(,)?) => {
+        match $val {
+            tmp => {
+                eprintln!("[{}:{}:{}] {} = {:#?}",
+                    file!(), line!(), column!(), stringify!($val), &tmp);
+                tmp
+            }
+        }
+    };
+    ($($val:expr),+ $(,)?) => {
+        ($(my_dbg!($val)),+,)
+    };
+}
+
+fn test_my_dbg() -> String {
+    let b: String = "".to_string();
+    my_dbg!(b, 1);
+    return b; //~ ERROR use of moved value:
+}
+
+fn test_not_macro() -> String {
+    let a = String::new();
+    let _b = match a {
+        tmp => {
+            eprintln!("dbg: {}", tmp);
+            tmp
+        }
+    };
+    return a; //~ ERROR use of moved value:
 }
 
 fn get_expr(_s: String) {}
 
-// The suggestion is purely syntactic; applying it here will result in a type error.
 fn test() {
     let a: String = "".to_string();
-    let _res = get_expr(dbg!(a)); //~ HELP consider borrowing instead of transferring ownership
+    let _res = get_expr(dbg!(a));
     let _l = a.len(); //~ ERROR borrow of moved value
 }