don't remove dbg! in arbitrary expressions

clippy_lints/src/dbg_macro.rs

@@ -3,10 +3,10 @@ use clippy_utils::macros::root_macro_call_first_node;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::{is_in_cfg_test, is_in_test_function};
 use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind};
+use rustc_hir::{Expr, ExprKind, Node, Stmt, StmtKind};
-use rustc_lint::{LateContext, LateLintPass};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::sym;
+use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -31,6 +31,11 @@ declare_clippy_lint! {
     "`dbg!` macro is intended as a debugging tool"
 }
 
+fn span_including_semi(cx: &LateContext<'_>, span: Span) -> Span {
+    let span = cx.sess().source_map().span_extend_to_next_char(span, ';', true);
+    span.with_hi(span.hi() + rustc_span::BytePos(1))
+}
+
 #[derive(Copy, Clone)]
 pub struct DbgMacro {
     allow_dbg_in_tests: bool,
@@ -55,13 +60,24 @@ impl LateLintPass<'_> for DbgMacro {
                 return;
             }
             let mut applicability = Applicability::MachineApplicable;
-            let suggestion = match expr.peel_drop_temps().kind {
+
-                // dbg!()
+            let (sugg_span, suggestion) = match expr.peel_drop_temps().kind {
-                ExprKind::Block(_, _) => String::new(),
+                ExprKind::Block(..) => match cx.tcx.hir().find_parent(expr.hir_id) {
-                // dbg!(1)
+                    // dbg!() as a standalone statement, suggest removing the whole statement entirely
-                ExprKind::Match(val, ..) => {
+                    Some(Node::Stmt(
-                    snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability).to_string()
+                        stmt @ Stmt {
+                            kind: StmtKind::Semi(_),
+                            ..
                         },
+                    )) => (span_including_semi(cx, stmt.span.source_callsite()), String::new()),
+                    // empty dbg!() in arbitrary position (e.g. `foo(dbg!())`), suggest replacing with `foo(())`
+                    _ => (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(
                     [
@@ -82,7 +98,7 @@ impl LateLintPass<'_> for DbgMacro {
                         "..",
                         &mut applicability,
                     );
-                    format!("({snippet})")
+                    (macro_call.span, format!("({snippet})"))
                 },
                 _ => return,
             };
@@ -90,7 +106,7 @@ impl LateLintPass<'_> for DbgMacro {
             span_lint_and_sugg(
                 cx,
                 DBG_MACRO,
-                macro_call.span,
+                sugg_span,
                 "the `dbg!` macro is intended as a debugging tool",
                 "remove the invocation before committing it to a version control system",
                 suggestion,

tests/ui/dbg_macro.rs

@@ -4,6 +4,7 @@
 fn foo(n: u32) -> u32 {
     if let Some(n) = dbg!(n.checked_sub(4)) { n } else { n }
 }
+fn bar(_: ()) {}
 
 fn factorial(n: u32) -> u32 {
     if dbg!(n <= 1) {
@@ -21,6 +22,13 @@ fn main() {
     dbg!(1, 2, 3, 4, 5);
 }
 
+fn issue9914() {
+    dbg!();
+    #[allow(clippy::let_unit_value)]
+    let _ = dbg!();
+    bar(dbg!());
+}
+
 mod issue7274 {
     trait Thing<'b> {
         fn foo(&self);

tests/ui/dbg_macro.stderr

@@ -11,7 +11,7 @@ LL |     if let Some(n) = n.checked_sub(4) { n } else { n }
    |                      ~~~~~~~~~~~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:9:8
+  --> $DIR/dbg_macro.rs:10:8
    |
 LL |     if dbg!(n <= 1) {
    |        ^^^^^^^^^^^^
@@ -22,7 +22,7 @@ LL |     if n <= 1 {
    |        ~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:10:9
+  --> $DIR/dbg_macro.rs:11:9
    |
 LL |         dbg!(1)
    |         ^^^^^^^
@@ -33,7 +33,7 @@ LL |         1
    |
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:12:9
+  --> $DIR/dbg_macro.rs:13:9
    |
 LL |         dbg!(n * factorial(n - 1))
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -44,7 +44,7 @@ LL |         n * factorial(n - 1)
    |
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:17:5
+  --> $DIR/dbg_macro.rs:18:5
    |
 LL |     dbg!(42);
    |     ^^^^^^^^
@@ -55,7 +55,7 @@ LL |     42;
    |     ~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:18:5
+  --> $DIR/dbg_macro.rs:19:5
    |
 LL |     dbg!(dbg!(dbg!(42)));
    |     ^^^^^^^^^^^^^^^^^^^^
@@ -66,7 +66,7 @@ LL |     dbg!(dbg!(42));
    |     ~~~~~~~~~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:19:14
+  --> $DIR/dbg_macro.rs:20:14
    |
 LL |     foo(3) + dbg!(factorial(4));
    |              ^^^^^^^^^^^^^^^^^^
@@ -77,7 +77,7 @@ LL |     foo(3) + factorial(4);
    |              ~~~~~~~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:20:5
+  --> $DIR/dbg_macro.rs:21:5
    |
 LL |     dbg!(1, 2, dbg!(3, 4));
    |     ^^^^^^^^^^^^^^^^^^^^^^
@@ -88,7 +88,7 @@ LL |     (1, 2, dbg!(3, 4));
    |     ~~~~~~~~~~~~~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:21:5
+  --> $DIR/dbg_macro.rs:22:5
    |
 LL |     dbg!(1, 2, 3, 4, 5);
    |     ^^^^^^^^^^^^^^^^^^^
@@ -99,7 +99,41 @@ LL |     (1, 2, 3, 4, 5);
    |     ~~~~~~~~~~~~~~~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:41:9
+  --> $DIR/dbg_macro.rs:26:5
+   |
+LL |     dbg!();
+   |     ^^^^^^^
+   |
+help: remove the invocation before committing it to a version control system
+   |
+LL -     dbg!();
+LL +     
+   |
+
+error: the `dbg!` macro is intended as a debugging tool
+  --> $DIR/dbg_macro.rs:28:13
+   |
+LL |     let _ = dbg!();
+   |             ^^^^^^
+   |
+help: remove the invocation before committing it to a version control system
+   |
+LL |     let _ = ();
+   |             ~~
+
+error: the `dbg!` macro is intended as a debugging tool
+  --> $DIR/dbg_macro.rs:29:9
+   |
+LL |     bar(dbg!());
+   |         ^^^^^^
+   |
+help: remove the invocation before committing it to a version control system
+   |
+LL |     bar(());
+   |         ~~
+
+error: the `dbg!` macro is intended as a debugging tool
+  --> $DIR/dbg_macro.rs:49:9
    |
 LL |         dbg!(2);
    |         ^^^^^^^
@@ -110,7 +144,7 @@ LL |         2;
    |         ~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:47:5
+  --> $DIR/dbg_macro.rs:55:5
    |
 LL |     dbg!(1);
    |     ^^^^^^^
@@ -121,7 +155,7 @@ LL |     1;
    |     ~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:52:5
+  --> $DIR/dbg_macro.rs:60:5
    |
 LL |     dbg!(1);
    |     ^^^^^^^
@@ -132,7 +166,7 @@ LL |     1;
    |     ~
 
 error: the `dbg!` macro is intended as a debugging tool
-  --> $DIR/dbg_macro.rs:58:9
+  --> $DIR/dbg_macro.rs:66:9
    |
 LL |         dbg!(1);
    |         ^^^^^^^
@@ -142,5 +176,5 @@ help: remove the invocation before committing it to a version control system
 LL |         1;
    |         ~
 
-error: aborting due to 13 previous errors
+error: aborting due to 16 previous errors