From 6fb812a5bbdca0ee68697b07060d80c916c89774 Mon Sep 17 00:00:00 2001
From: Chris Kipp <ckipp@pm.me>
Date: Mon, 19 Jun 2023 15:32:48 +0200
Subject: [PATCH] fix: report correct location on a repeat modifier (#17982)

Currently given the following code snippet:

```scala
final final case class Foo()
```

The error is reported on `Foo` and not on the repeated modifier. This
changes the reporting to instead report on the repeated modifier
`final`.

Fixes #17981
[Cherry-picked 10180da5de14be45be59200f2a54c44e9ad94d46]
---
 compiler/src/dotty/tools/dotc/parsing/Parsers.scala | 4 +++-
 tests/neg/i17981.check                              | 6 ++++++
 tests/neg/i17981.scala                              | 1 +
 3 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 tests/neg/i17981.check
 create mode 100644 tests/neg/i17981.scala

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 3079b26df6cd..493a6e1cc18e 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -3028,7 +3028,9 @@ object Parsers {
       val name = in.name
       val mod = atSpan(in.skipToken()) { modOfToken(tok, name) }
 
-      if (mods.isOneOf(mod.flags)) syntaxError(RepeatedModifier(mod.flags.flagsString))
+      if mods.isOneOf(mod.flags) then
+        syntaxError(RepeatedModifier(mod.flags.flagsString), mod.span)
+
       addMod(mods, mod)
     }
 
diff --git a/tests/neg/i17981.check b/tests/neg/i17981.check
new file mode 100644
index 000000000000..0ef7225d857e
--- /dev/null
+++ b/tests/neg/i17981.check
@@ -0,0 +1,6 @@
+-- [E015] Syntax Error: tests/neg/i17981.scala:1:6 ---------------------------------------------------------------------
+1 |final final case class Foo() // error
+  |      ^^^^^
+  |      Repeated modifier final
+  |
+  | longer explanation available when compiling with `-explain`
diff --git a/tests/neg/i17981.scala b/tests/neg/i17981.scala
new file mode 100644
index 000000000000..d2eaa0cfa7f2
--- /dev/null
+++ b/tests/neg/i17981.scala
@@ -0,0 +1 @@
+final final case class Foo() // error