fix #104440

compiler/rustc_lint/src/context.rs

@@ -825,34 +825,39 @@ pub trait LintContext: Sized {
                     debug!(?param_span, ?use_span, ?deletion_span);
                     db.span_label(param_span, "this lifetime...");
                     db.span_label(use_span, "...is used only here");
-                    let msg = "elide the single-use lifetime";
-                    let (use_span, replace_lt) = if elide {
-                        let use_span = sess.source_map().span_extend_while(
-                            use_span,
-                            char::is_whitespace,
-                        ).unwrap_or(use_span);
-                        (use_span, String::new())
-                    } else {
-                        (use_span, "'_".to_owned())
-                    };
-                    db.multipart_suggestion(
-                        msg,
-                        vec![(deletion_span, String::new()), (use_span, replace_lt)],
-                        Applicability::MachineApplicable,
-                    );
+                    if let Some(deletion_span) = deletion_span {
+                        let msg = "elide the single-use lifetime";
+                        let (use_span, replace_lt) = if elide {
+                            let use_span = sess.source_map().span_extend_while(
+                                use_span,
+                                char::is_whitespace,
+                            ).unwrap_or(use_span);
+                            (use_span, String::new())
+                        } else {
+                            (use_span, "'_".to_owned())
+                        };
+                        debug!(?deletion_span, ?use_span);
+                        db.multipart_suggestion(
+                            msg,
+                            vec![(deletion_span, String::new()), (use_span, replace_lt)],
+                            Applicability::MachineApplicable,
+                        );
+                    }
                 },
                 BuiltinLintDiagnostics::SingleUseLifetime {
                     param_span: _,
                     use_span: None,
                     deletion_span,
                 } => {
                     debug!(?deletion_span);
-                    db.span_suggestion(
-                        deletion_span,
-                        "elide the unused lifetime",
-                        "",
-                        Applicability::MachineApplicable,
-                    );
+                    if let Some(deletion_span) = deletion_span {
+                        db.span_suggestion(
+                            deletion_span,
+                            "elide the unused lifetime",
+                            "",
+                            Applicability::MachineApplicable,
+                        );
+                    }
                 },
                 BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
                     db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");

compiler/rustc_lint_defs/src/lib.rs

@@ -502,7 +502,7 @@ pub enum BuiltinLintDiagnostics {
         param_span: Span,
         /// Span of the code that should be removed when eliding this lifetime.
         /// This span should include leading or trailing comma.
-        deletion_span: Span,
+        deletion_span: Option<Span>,
         /// Span of the single use, or None if the lifetime is never used.
         /// If true, the lifetime will be fully elided.
         use_span: Option<(Span, bool)>,

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -2188,15 +2188,31 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             let deletion_span = || {
                 if params.len() == 1 {
                     // if sole lifetime, remove the entire `<>` brackets
-                    generics_span
+                    Some(generics_span)
                 } else if param_index == 0 {
                     // if removing within `<>` brackets, we also want to
                     // delete a leading or trailing comma as appropriate
-                    param.span().to(params[param_index + 1].span().shrink_to_lo())
+                    match (
+                        param.span().find_ancestor_inside(generics_span),
+                        params[param_index + 1].span().find_ancestor_inside(generics_span),
+                    ) {
+                        (Some(param_span), Some(next_param_span)) => {
+                            Some(param_span.to(next_param_span.shrink_to_lo()))
+                        }
+                        _ => None,
+                    }
                 } else {
                     // if removing within `<>` brackets, we also want to
                     // delete a leading or trailing comma as appropriate
-                    params[param_index - 1].span().shrink_to_hi().to(param.span())
+                    match (
+                        param.span().find_ancestor_inside(generics_span),
+                        params[param_index - 1].span().find_ancestor_inside(generics_span),
+                    ) {
+                        (Some(param_span), Some(prev_param_span)) => {
+                            Some(prev_param_span.shrink_to_hi().to(param_span))
+                        }
+                        _ => None,
+                    }
                 }
             };
             match use_set {

tests/ui/single-use-lifetime/issue-104440.rs

@@ -0,0 +1,100 @@
+#![feature(decl_macro, rustc_attrs)]
+#![deny(single_use_lifetimes)]
+
+mod type_params {
+    macro m($T:ident) {
+        fn f<$T: Clone, T: PartialEq>(t1: $T, t2: T) -> ($T, bool) {
+            (t1.clone(), t2 == t2)
+        }
+    }
+
+    #[rustc_macro_transparency = "semitransparent"]
+    macro n($T:ident) {
+        fn g<$T: Clone>(t1: $T, t2: T) -> (T, $T) {
+            (t1.clone(), t2.clone())
+        }
+        fn h<T: Clone>(t1: $T, t2: T) -> (T, $T) {
+            (t1.clone(), t2.clone())
+        }
+    }
+
+    #[rustc_macro_transparency = "transparent"]
+    macro p($T:ident) {
+        fn j<$T: Clone>(t1: $T, t2: T) -> (T, $T) {
+            (t1.clone(), t2.clone())
+        }
+        fn k<T: Clone>(t1: $T, t2: T) -> (T, $T) {
+            (t1.clone(), t2.clone())
+        }
+    }
+
+    m!(T);
+    n!(T);
+    p!(T);
+}
+
+mod lifetime_params {
+    macro m($a:lifetime) {
+        fn f<'b, 'c, $a: 'b, 'a: 'c>(t1: &$a(), t2: &'a ()) -> (&'b (), &'c ()) { //~ ERROR lifetime parameter `'a` only used once
+            (t1, t2)
+        }
+    }
+
+    #[rustc_macro_transparency = "semitransparent"]
+    macro n($a:lifetime) {
+        fn g<$a>(t1: &$a(), t2: &'a ()) -> (&'a (), &$a ()) {
+            (t1, t2)
+        }
+        fn h<'a>(t1: &$a(), t2: &'a ()) -> (&'a (), &$a ()) {
+            (t1, t2)
+        }
+    }
+
+    #[rustc_macro_transparency = "transparent"]
+    macro p($a:lifetime) {
+        fn j<$a>(t1: &$a(), t2: &'a ()) -> (&'a (), &$a ()) {
+            (t1, t2)
+        }
+        fn k<'a>(t1: &$a(), t2: &'a ()) -> (&'a (), &$a ()) {
+            (t1, t2)
+        }
+    }
+
+    m!('a); //~ ERROR lifetime parameter `'a` only used once
+    n!('a);
+    p!('a);
+}
+
+mod const_params {
+    macro m($C:ident) {
+        fn f<const $C: usize, const C: usize>(t1: [(); $C], t2: [(); C]) -> ([(); $C], [(); C]) {
+            (t1, t2)
+        }
+    }
+
+    #[rustc_macro_transparency = "semitransparent"]
+    macro n($C:ident) {
+        fn g<const $C: usize>(t1: [(); $C], t2: [(); C]) -> ([(); C], [(); $C]) {
+            (t1, t2)
+        }
+        fn h<const C: usize>(t1: [(); $C], t2: [(); C]) -> ([(); C], [(); $C]) {
+            (t1, t2)
+        }
+    }
+
+    #[rustc_macro_transparency = "transparent"]
+    macro p($C:ident) {
+        fn j<const $C: usize>(t1: [(); $C], t2: [(); C]) -> ([(); C], [(); $C]) {
+            (t1, t2)
+        }
+        fn k<const C: usize>(t1: [(); $C], t2: [(); C]) -> ([(); C], [(); $C]) {
+            (t1, t2)
+        }
+    }
+
+    m!(C);
+    n!(C);
+    p!(C);
+}
+
+fn main() {}

tests/ui/single-use-lifetime/issue-104440.stderr

@@ -0,0 +1,28 @@
+error: lifetime parameter `'a` only used once
+  --> $DIR/issue-104440.rs:63:8
+   |
+LL |     m!('a);
+   |        ^^
+   |        |
+   |        this lifetime...
+   |        ...is used only here
+   |
+note: the lint level is defined here
+  --> $DIR/issue-104440.rs:2:9
+   |
+LL | #![deny(single_use_lifetimes)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+
+error: lifetime parameter `'a` only used once
+  --> $DIR/issue-104440.rs:38:30
+   |
+LL |         fn f<'b, 'c, $a: 'b, 'a: 'c>(t1: &$a(), t2: &'a ()) -> (&'b (), &'c ()) {
+   |                              ^^ this lifetime...     -- ...is used only here
+...
+LL |     m!('a);
+   |     ------ in this macro invocation
+   |
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+