Fix `dbg_macro` fail to handle async coroutine desugar (#14937)

Closes rust-lang/rust-clippy#14914

----

changelog: [`dbg_macro`]: fix mishandling of async coroutine desugar

4 files changed, 122 insertions, 46 deletions

diff --git a/clippy_lints/src/dbg_macro.rs b/clippy_lints/src/dbg_macro.rs
index 06376c57119..152516baf73 100644
--- a/clippy_lints/src/dbg_macro.rs
+++ b/clippy_lints/src/dbg_macro.rs
@@ -5,7 +5,7 @@ use clippy_utils::macros::{MacroCall, macro_backtrace};
 use clippy_utils::source::snippet_with_applicability;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind, Node};
+use rustc_hir::{Closure, ClosureKind, CoroutineKind, Expr, ExprKind, LetStmt, LocalSource, Node, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_session::impl_lint_pass;
 use rustc_span::{Span, SyntaxContext, sym};
@@ -60,6 +60,8 @@ impl LateLintPass<'_> for DbgMacro {
         if cur_syntax_ctxt != self.prev_ctxt &&
             let Some(macro_call) = first_dbg_macro_in_expansion(cx, expr.span) &&
             !macro_call.span.in_external_macro(cx.sess().source_map()) &&
+            // avoids exprs generated by the desugaring of coroutines
+            !is_coroutine_desugar(expr) &&
             self.checked_dbg_call_site.insert(macro_call.span) &&
             // allows `dbg!` in test code if allow-dbg-in-test is set to true in clippy.toml
             !(self.allow_dbg_in_tests && is_in_test(cx.tcx, expr.hir_id))
@@ -73,50 +75,51 @@ impl LateLintPass<'_> for DbgMacro {
                 "the `dbg!` macro is intended as a debugging tool",
                 |diag| {
                     let mut applicability = Applicability::MachineApplicable;
-
-                    let (sugg_span, suggestion) = match expr.peel_drop_temps().kind {
-                        // dbg!()
-                        ExprKind::Block(..) => {
-                            // If the `dbg!` macro is a "free" statement and not contained within other expressions,
-                            // remove the whole statement.
-                            if let Node::Stmt(_) = cx.tcx.parent_hir_node(expr.hir_id)
-                                && let Some(semi_span) = cx.sess().source_map().mac_call_stmt_semi_span(macro_call.span)
-                            {
-                                (macro_call.span.to(semi_span), String::new())
-                            } else {
-                                (macro_call.span, String::from("()"))
-                            }
-                        },
-                        // 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, ..),
-                                    ..
-                                },
-                                ..,
-                                Expr {
-                                    kind: ExprKind::Match(last, ..),
-                                    ..
-                                },
-                            ],
-                        ) => {
-                            let snippet = snippet_with_applicability(
-                                cx,
-                                first.span.source_callsite().to(last.span.source_callsite()),
-                                "..",
-                                &mut applicability,
-                            );
-                            (macro_call.span, format!("({snippet})"))
-                        },
-                        _ => unreachable!(),
-                    };
+                    let (sugg_span, suggestion) =
+                        match is_async_move_desugar(expr).unwrap_or(expr).peel_drop_temps().kind {
+                            // dbg!()
+                            ExprKind::Block(..) => {
+                                // If the `dbg!` macro is a "free" statement and not contained within other expressions,
+                                // remove the whole statement.
+                                if let Node::Stmt(_) = cx.tcx.parent_hir_node(expr.hir_id)
+                                    && let Some(semi_span) =
+                                        cx.sess().source_map().mac_call_stmt_semi_span(macro_call.span)
+                                {
+                                    (macro_call.span.to(semi_span), String::new())
+                                } else {
+                                    (macro_call.span, String::from("()"))
+                                }
+                            },
+                            // 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, ..),
+                                        ..
+                                    },
+                                    ..,
+                                    Expr {
+                                        kind: ExprKind::Match(last, ..),
+                                        ..
+                                    },
+                                ],
+                            ) => {
+                                let snippet = snippet_with_applicability(
+                                    cx,
+                                    first.span.source_callsite().to(last.span.source_callsite()),
+                                    "..",
+                                    &mut applicability,
+                                );
+                                (macro_call.span, format!("({snippet})"))
+                            },
+                            _ => unreachable!(),
+                        };
 
                     diag.span_suggestion(
                         sugg_span,
@@ -134,6 +137,35 @@ impl LateLintPass<'_> for DbgMacro {
     }
 }
 
+fn is_coroutine_desugar(expr: &Expr<'_>) -> bool {
+    matches!(
+        expr.kind,
+        ExprKind::Closure(Closure {
+            kind: ClosureKind::Coroutine(CoroutineKind::Desugared(..)) | ClosureKind::CoroutineClosure(..),
+            ..
+        })
+    )
+}
+
+fn is_async_move_desugar<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
+    if let ExprKind::Block(block, _) = expr.kind
+        && let [
+            Stmt {
+                kind:
+                    StmtKind::Let(LetStmt {
+                        source: LocalSource::AsyncFn,
+                        ..
+                    }),
+                ..
+            },
+        ] = block.stmts
+    {
+        return block.expr;
+    }
+
+    None
+}
+
 fn first_dbg_macro_in_expansion(cx: &LateContext<'_>, span: Span) -> Option<MacroCall> {
     macro_backtrace(span).find(|mc| cx.tcx.is_diagnostic_item(sym::dbg_macro, mc.def_id))
 }
diff --git a/tests/ui/dbg_macro/dbg_macro.fixed b/tests/ui/dbg_macro/dbg_macro.fixed
index 3b9dee81898..5993c2faf0d 100644
--- a/tests/ui/dbg_macro/dbg_macro.fixed
+++ b/tests/ui/dbg_macro/dbg_macro.fixed
@@ -123,3 +123,19 @@ mod issue12131 {
         //~^ dbg_macro
     }
 }
+
+mod issue14914 {
+    use std::future::Future;
+
+    fn takes_async_fn<F, Fut>(_f: F)
+    where
+        F: FnOnce(i32) -> Fut,
+        Fut: Future<Output = i32>,
+    {
+    }
+
+    fn should_not_panic() {
+        takes_async_fn(async |val| val);
+        //~^ dbg_macro
+    }
+}
diff --git a/tests/ui/dbg_macro/dbg_macro.rs b/tests/ui/dbg_macro/dbg_macro.rs
index 1dbbc6fe984..58d7e106e23 100644
--- a/tests/ui/dbg_macro/dbg_macro.rs
+++ b/tests/ui/dbg_macro/dbg_macro.rs
@@ -123,3 +123,19 @@ mod issue12131 {
         //~^ dbg_macro
     }
 }
+
+mod issue14914 {
+    use std::future::Future;
+
+    fn takes_async_fn<F, Fut>(_f: F)
+    where
+        F: FnOnce(i32) -> Fut,
+        Fut: Future<Output = i32>,
+    {
+    }
+
+    fn should_not_panic() {
+        takes_async_fn(async |val| dbg!(val));
+        //~^ dbg_macro
+    }
+}
diff --git a/tests/ui/dbg_macro/dbg_macro.stderr b/tests/ui/dbg_macro/dbg_macro.stderr
index f1412023cc8..5a65b38a85c 100644
--- a/tests/ui/dbg_macro/dbg_macro.stderr
+++ b/tests/ui/dbg_macro/dbg_macro.stderr
@@ -230,5 +230,17 @@ LL -         print!("{}", dbg!(s));
 LL +         print!("{}", s);
    |
 
-error: aborting due to 19 previous errors
+error: the `dbg!` macro is intended as a debugging tool
+  --> tests/ui/dbg_macro/dbg_macro.rs:138:36
+   |
+LL |         takes_async_fn(async |val| dbg!(val));
+   |                                    ^^^^^^^^^
+   |
+help: remove the invocation before committing it to a version control system
+   |
+LL -         takes_async_fn(async |val| dbg!(val));
+LL +         takes_async_fn(async |val| val);
+   |
+
+error: aborting due to 20 previous errors