Rollup merge of #149869 - joboet:torn-dbg, r=Mark-Simulacrum
std: avoid tearing `dbg!` prints Fixes https://github.com/rust-lang/rust/issues/136703. This is an alternative to rust-lang/rust#149859. Instead of formatting everything into a string, this PR makes multi-expression `dbg!` expand into multiple nested matches, with the final match containing a single `eprint!`. By using macro recursion and relying on hygiene, this allows naming every bound value in that `eprint!`. CC @orlp r? libs
This commit is contained in:
Matthias Krüger
GitHub
commit
cc666ba8f4
12 changed files with 125 additions and 64 deletions
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@ -468,7 +468,9 @@ extern crate std as realstd;
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// The standard macros that are not built-in to the compiler.
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#[macro_use]
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mod macros;
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#[doc(hidden)]
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#[unstable(feature = "std_internals", issue = "none")]
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pub mod macros;
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// The runtime entry point and a few unstable public functions used by the
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// compiler
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@ -347,35 +347,70 @@ macro_rules! eprintln {
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/// [`debug!`]: https://docs.rs/log/*/log/macro.debug.html
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/// [`log`]: https://crates.io/crates/log
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#[macro_export]
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#[allow_internal_unstable(std_internals)]
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#[cfg_attr(not(test), rustc_diagnostic_item = "dbg_macro")]
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#[stable(feature = "dbg_macro", since = "1.32.0")]
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macro_rules! dbg {
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// NOTE: We cannot use `concat!` to make a static string as a format argument
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// of `eprintln!` because `file!` could contain a `{` or
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// `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
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// will be malformed.
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() => {
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$crate::eprintln!("[{}:{}:{}]", $crate::file!(), $crate::line!(), $crate::column!())
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};
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($val:expr $(,)?) => {
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($($val:expr),+ $(,)?) => {
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$crate::macros::dbg_internal!(() () ($($val),+))
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};
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}
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/// Internal macro that processes a list of expressions and produces a chain of
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/// nested `match`es, one for each expression, before finally calling `eprint!`
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/// with the collected information and returning all the evaluated expressions
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/// in a tuple.
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///
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/// E.g. `dbg_internal!(() () (1, 2))` expands into
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/// ```rust, ignore
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/// match 1 {
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/// tmp_1 => match 2 {
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/// tmp_2 => {
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/// eprint!("...", &tmp_1, &tmp_2, /* some other arguments */);
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/// (tmp_1, tmp_2)
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/// }
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/// }
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/// }
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/// ```
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///
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/// This is necessary so that `dbg!` outputs don't get torn, see #136703.
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#[doc(hidden)]
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#[rustc_macro_transparency = "semiopaque"]
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pub macro dbg_internal {
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(($($piece:literal),+) ($($processed:expr => $bound:expr),+) ()) => {{
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$crate::eprint!(
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$crate::concat!($($piece),+),
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$(
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$crate::stringify!($processed),
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// The `&T: Debug` check happens here (not in the format literal desugaring)
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// to avoid format literal related messages and suggestions.
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&&$bound as &dyn $crate::fmt::Debug
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),+,
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// The location returned here is that of the macro invocation, so
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// it will be the same for all expressions. Thus, label these
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// arguments so that they can be reused in every piece of the
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// formatting template.
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file=$crate::file!(),
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line=$crate::line!(),
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column=$crate::column!()
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);
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// Comma separate the variables only when necessary so that this will
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// not yield a tuple for a single expression, but rather just parenthesize
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// the expression.
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($($bound),+)
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}},
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(($($piece:literal),*) ($($processed:expr => $bound:expr),*) ($val:expr $(,$rest:expr)*)) => {
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// Use of `match` here is intentional because it affects the lifetimes
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// of temporaries - https://stackoverflow.com/a/48732525/1063961
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match $val {
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tmp => {
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$crate::eprintln!("[{}:{}:{}] {} = {:#?}",
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$crate::file!(),
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$crate::line!(),
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$crate::column!(),
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$crate::stringify!($val),
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// The `&T: Debug` check happens here (not in the format literal desugaring)
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// to avoid format literal related messages and suggestions.
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&&tmp as &dyn $crate::fmt::Debug,
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);
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tmp
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}
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tmp => $crate::macros::dbg_internal!(
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($($piece,)* "[{file}:{line}:{column}] {} = {:#?}\n")
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($($processed => $bound,)* $val => tmp)
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($($rest),*)
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),
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}
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};
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($($val:expr),+ $(,)?) => {
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($($crate::dbg!($val)),+,)
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};
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},
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}
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@ -5,7 +5,7 @@ use clippy_utils::macros::{MacroCall, macro_backtrace};
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use clippy_utils::source::snippet_with_applicability;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_errors::Applicability;
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use rustc_hir::{Closure, ClosureKind, CoroutineKind, Expr, ExprKind, LetStmt, LocalSource, Node, Stmt, StmtKind};
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use rustc_hir::{Arm, Closure, ClosureKind, CoroutineKind, Expr, ExprKind, LetStmt, LocalSource, Node, Stmt, StmtKind};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_session::impl_lint_pass;
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use rustc_span::{Span, SyntaxContext, sym};
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@ -90,33 +90,27 @@ impl LateLintPass<'_> for DbgMacro {
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(macro_call.span, String::from("()"))
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}
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},
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// dbg!(1)
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ExprKind::Match(val, ..) => (
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macro_call.span,
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snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability)
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.to_string(),
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),
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// dbg!(2, 3)
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ExprKind::Tup(
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[
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Expr {
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kind: ExprKind::Match(first, ..),
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..
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},
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..,
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Expr {
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kind: ExprKind::Match(last, ..),
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..
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},
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],
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) => {
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let snippet = snippet_with_applicability(
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cx,
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first.span.source_callsite().to(last.span.source_callsite()),
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"..",
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&mut applicability,
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);
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(macro_call.span, format!("({snippet})"))
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ExprKind::Match(first, arms, _) => {
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let vals = collect_vals(first, arms);
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let suggestion = match vals.as_slice() {
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// dbg!(1) => 1
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&[val] => {
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snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability)
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.to_string()
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}
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// dbg!(2, 3) => (2, 3)
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&[first, .., last] => {
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let snippet = snippet_with_applicability(
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cx,
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first.span.source_callsite().to(last.span.source_callsite()),
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"..",
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&mut applicability,
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);
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format!("({snippet})")
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}
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_ => unreachable!(),
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};
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(macro_call.span, suggestion)
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},
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_ => unreachable!(),
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};
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@ -169,3 +163,33 @@ fn is_async_move_desugar<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx
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fn first_dbg_macro_in_expansion(cx: &LateContext<'_>, span: Span) -> Option<MacroCall> {
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macro_backtrace(span).find(|mc| cx.tcx.is_diagnostic_item(sym::dbg_macro, mc.def_id))
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}
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/// Extracts all value expressions from the `match`-tree generated by `dbg!`.
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///
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/// E.g. from
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/// ```rust, ignore
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/// match 1 {
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/// tmp_1 => match 2 {
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/// tmp_2 => {
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/// /* printing */
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/// (tmp_1, tmp_2)
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/// }
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/// }
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/// }
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/// ```
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/// this extracts `1` and `2`.
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fn collect_vals<'hir>(first: &'hir Expr<'hir>, mut arms: &'hir [Arm<'hir>]) -> Vec<&'hir Expr<'hir>> {
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let mut vals = vec![first];
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loop {
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let [arm] = arms else { unreachable!("dbg! macro expansion only has single-arm matches") };
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match is_async_move_desugar(arm.body).unwrap_or(arm.body).peel_drop_temps().kind {
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ExprKind::Block(..) => return vals,
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ExprKind::Match(val, a, _) => {
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vals.push(val);
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arms = a;
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}
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_ => unreachable!("dbg! macro expansion only results in block or match expressions"),
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}
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}
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}
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@ -16,7 +16,7 @@ help: ALLOC was deallocated here:
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LL | };
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| ^
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
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@ -11,7 +11,7 @@ LL | dbg!(x.0);
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= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
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= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
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ALLOC (stack variable, size: 132, align: 4) {
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@ -4,7 +4,7 @@ error[E0106]: missing lifetime specifier
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LL | dbg!(b);
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| ^^^^^^^ expected named lifetime parameter
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0425]: cannot find function `a` in this scope
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--> $DIR/ice-line-bounds-issue-148732.rs:1:7
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@ -37,7 +37,7 @@ LL | dbg!(b);
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| ^^^^^^^ the trait `Debug` is not implemented for fn item `fn() {b}`
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= help: use parentheses to call this function: `b()`
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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error: aborting due to 4 previous errors
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@ -4,7 +4,7 @@ error[E0308]: mismatched types
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LL | x => dbg!(x),
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| ^^^^^^^ expected `()`, found integer
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: you might have meant to return this value
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LL | x => return dbg!(x),
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@ -16,7 +16,7 @@ error[E0308]: mismatched types
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LL | dbg!(x)
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| ^^^^^^^ expected `()`, found integer
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: you might have meant to return this value
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LL | return dbg!(x)
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@ -28,7 +28,7 @@ error[E0308]: mismatched types
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LL | _ => dbg!(1)
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| ^^^^^^^ expected `()`, found integer
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: you might have meant to return this value
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LL | _ => return dbg!(1)
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@ -40,7 +40,7 @@ error[E0308]: mismatched types
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LL | _ => {dbg!(1)}
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| ^^^^^^^ expected `()`, found integer
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: you might have meant to return this value
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LL | _ => {return dbg!(1)}
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@ -5,7 +5,7 @@ error[E0277]: `Dummy` doesn't implement `Debug`
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| ^^^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `Dummy`
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= note: add `#[derive(Debug)]` to `Dummy` or manually `impl Debug for Dummy`
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider annotating `Dummy` with `#[derive(Debug)]`
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--> $DIR/auxiliary/dummy_lib.rs:2:1
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@ -8,7 +8,7 @@ LL | let _ = dbg!(a);
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LL | let _ = dbg!(a);
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| ^^^^^^^ value used here after move
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider borrowing instead of transferring ownership
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LL | let _ = dbg!(&a);
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@ -5,7 +5,7 @@ LL | let _: NotDebug = dbg!(NotDebug);
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| ^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `NotDebug`
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= note: add `#[derive(Debug)]` to `NotDebug` or manually `impl Debug for NotDebug`
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider annotating `NotDebug` with `#[derive(Debug)]`
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LL + #[derive(Debug)]
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@ -15,7 +15,7 @@ error[E0308]: mismatched types
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LL | b"abc".iter().for_each(|x| dbg!(x));
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| ^^^^^^^ expected `()`, found `&u8`
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0308]: mismatched types
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--> $DIR/closure-ty-mismatch-issue-128561.rs:8:9
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@ -26,7 +26,7 @@ error[E0308]: mismatched types
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LL | let c: S = dbg!(field);
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| ^^^^^^^^^^^ expected `S`, found `&S`
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|
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider using clone here
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LL | let c: S = dbg!(field).clone();
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@ -38,7 +38,7 @@ error[E0308]: mismatched types
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LL | let c: S = dbg!(dbg!(field));
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| ^^^^^^^^^^^^^^^^^ expected `S`, found `&S`
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|
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= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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= note: this error originates in the macro `$crate::macros::dbg_internal` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider using clone here
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|
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LL | let c: S = dbg!(dbg!(field)).clone();
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