From 2c3bb42ebd86247ea5d2fb4daa51d9ada3f6ae61 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 19 Jun 2022 16:27:26 -0700
Subject: [PATCH] Only omit trailing comma if block doesn't come from macro
 expansion

---
 .../src/thir/pattern/check_match.rs           | 17 ++++++++++++---
 src/test/ui/issue-94866.rs                    | 14 +++++++++++++
 src/test/ui/issue-94866.stderr                | 21 +++++++++++++++++++
 .../tuple-struct-nonexhaustive.stderr         |  2 +-
 4 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 src/test/ui/issue-94866.rs
 create mode 100644 src/test/ui/issue-94866.stderr

diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index dc204eb47ae..51aebfef8ac 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -829,7 +829,13 @@ fn non_exhaustive_match<'p, 'tcx>(
             } else {
                 " ".to_string()
             };
-            let comma = if matches!(only.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
+            let comma = if matches!(only.body.kind, hir::ExprKind::Block(..))
+                && only.span.ctxt() == only.body.span.ctxt()
+            {
+                ""
+            } else {
+                ","
+            };
             suggestion = Some((
                 only.span.shrink_to_hi(),
                 format!("{}{}{} => todo!()", comma, pre_indentation, pattern),
@@ -837,8 +843,13 @@ fn non_exhaustive_match<'p, 'tcx>(
         }
         [.., prev, last] if prev.span.ctxt() == last.span.ctxt() => {
             if let Ok(snippet) = sm.span_to_snippet(prev.span.between(last.span)) {
-                let comma =
-                    if matches!(last.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
+                let comma = if matches!(last.body.kind, hir::ExprKind::Block(..))
+                    && last.span.ctxt() == last.body.span.ctxt()
+                {
+                    ""
+                } else {
+                    ","
+                };
                 suggestion = Some((
                     last.span.shrink_to_hi(),
                     format!(
diff --git a/src/test/ui/issue-94866.rs b/src/test/ui/issue-94866.rs
new file mode 100644
index 00000000000..c4203487936
--- /dev/null
+++ b/src/test/ui/issue-94866.rs
@@ -0,0 +1,14 @@
+macro_rules! m {
+    () => {
+        {}
+    };
+}
+
+enum Enum { A, B }
+
+fn main() {
+    match Enum::A {
+    //~^ ERROR non-exhaustive patterns
+    Enum::A => m!()
+    }
+}
diff --git a/src/test/ui/issue-94866.stderr b/src/test/ui/issue-94866.stderr
new file mode 100644
index 00000000000..5477d83f449
--- /dev/null
+++ b/src/test/ui/issue-94866.stderr
@@ -0,0 +1,21 @@
+error[E0004]: non-exhaustive patterns: `B` not covered
+  --> $DIR/issue-94866.rs:10:11
+   |
+LL |     match Enum::A {
+   |           ^^^^^^^ pattern `B` not covered
+   |
+note: `Enum` defined here
+  --> $DIR/issue-94866.rs:7:16
+   |
+LL | enum Enum { A, B }
+   |      ----      ^ not covered
+   = note: the matched value is of type `Enum`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~     Enum::A => m!(),
+LL +     B => todo!()
+   |
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0004`.
diff --git a/src/test/ui/pattern/usefulness/tuple-struct-nonexhaustive.stderr b/src/test/ui/pattern/usefulness/tuple-struct-nonexhaustive.stderr
index fc0430d06fa..e2a65ff8524 100644
--- a/src/test/ui/pattern/usefulness/tuple-struct-nonexhaustive.stderr
+++ b/src/test/ui/pattern/usefulness/tuple-struct-nonexhaustive.stderr
@@ -12,7 +12,7 @@ LL | struct Foo(isize, isize);
    = note: the matched value is of type `Foo`
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
-LL ~         Foo(2, b) => println!("{}", b)
+LL ~         Foo(2, b) => println!("{}", b),
 LL +         Foo(_, _) => todo!()
    |
 
-- 
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