From 372ac9c1a29820f4393ba59eb49f81959bca2926 Mon Sep 17 00:00:00 2001
From: mejrs <>
Date: Mon, 9 Jan 2023 22:37:56 +0100
Subject: [PATCH] Translate `Overlap` eagerly

---
 .../locales/en-US/mir_build.ftl               |  2 --
 compiler/rustc_mir_build/src/errors.rs        | 19 +++++++++++++++----
 .../src/thir/pattern/deconstruct_pat.rs       |  9 +++------
 .../overlapping_range_endpoints.stderr        |  1 +
 4 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/mir_build.ftl b/compiler/rustc_error_messages/locales/en-US/mir_build.ftl
index 976614ecd9e..801a5b31e02 100644
--- a/compiler/rustc_error_messages/locales/en-US/mir_build.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/mir_build.ftl
@@ -323,8 +323,6 @@ mir_build_overlapping_range_endpoints = multiple patterns overlap on their endpo
     .range = ... with this range
     .note = you likely meant to write mutually exclusive ranges
 
-mir_build_overlapping_range = this range overlaps on `{$range}`...
-
 mir_build_non_exhaustive_omitted_pattern = some variants are not matched explicitly
     .help = ensure that all variants are matched explicitly by adding the suggested match arms
     .note = the matched value is of type `{$scrut_ty}` and the `non_exhaustive_omitted_patterns` attribute was found
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 1b2fbae2cd5..39b67d995fa 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -677,17 +677,28 @@ pub struct OverlappingRangeEndpoints<'tcx> {
     #[label(range)]
     pub range: Span,
     #[subdiagnostic]
-    pub overlap: Overlap<'tcx>,
+    pub overlap: Vec<Overlap<'tcx>>,
 }
 
-#[derive(Subdiagnostic)]
-#[label(mir_build_overlapping_range)]
 pub struct Overlap<'tcx> {
-    #[primary_span]
     pub span: Span,
     pub range: Pat<'tcx>,
 }
 
+impl<'tcx> AddToDiagnostic for Overlap<'tcx> {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
+        let Overlap { span, range } = self;
+
+        // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
+        // does not support `#[subdiagnostic(eager)]`...
+        let message = format!("this range overlaps on `{range}`...");
+        diag.span_label(span, message);
+    }
+}
+
 #[derive(LintDiagnostic)]
 #[diag(mir_build_non_exhaustive_omitted_pattern)]
 #[help]
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index 323df1b8147..17b3c475f83 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -285,19 +285,16 @@ pub(super) fn lint_overlapping_range_endpoints<'a, 'p: 'a, 'tcx: 'a>(
             return;
         }
 
-        // Get the first overlap. We get only the first rather than all of them
-        // because displaying multiple overlaps requires a way to eagerly translate
-        // lintdiagnostics, but that doesn't exist.
-        let overlap = pats
+        let overlap: Vec<_> = pats
             .filter_map(|pat| Some((pat.ctor().as_int_range()?, pat.span())))
             .filter(|(range, _)| self.suspicious_intersection(range))
             .map(|(range, span)| Overlap {
                 range: self.intersection(&range).unwrap().to_pat(pcx.cx.tcx, pcx.ty),
                 span,
             })
-            .next();
+            .collect();
 
-        if let Some(overlap) = overlap {
+        if !overlap.is_empty() {
             pcx.cx.tcx.emit_spanned_lint(
                 lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
                 hir_id,
diff --git a/tests/ui/pattern/usefulness/integer-ranges/overlapping_range_endpoints.stderr b/tests/ui/pattern/usefulness/integer-ranges/overlapping_range_endpoints.stderr
index a1c802add17..ea0e8f6e49e 100644
--- a/tests/ui/pattern/usefulness/integer-ranges/overlapping_range_endpoints.stderr
+++ b/tests/ui/pattern/usefulness/integer-ranges/overlapping_range_endpoints.stderr
@@ -59,6 +59,7 @@ error: multiple patterns overlap on their endpoints
 LL |         0..=10 => {}
    |         ------ this range overlaps on `10_u8`...
 LL |         20..=30 => {}
+   |         ------- this range overlaps on `20_u8`...
 LL |         10..=20 => {}
    |         ^^^^^^^ ... with this range
    |