From 089e42f8212c84e4756b00aa75d18a6d139fd940 Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Fri, 15 Nov 2024 13:57:29 +0100
Subject: [PATCH 1/2] Handle old given syntax where identifier and type are
 seperated by new line

---
 .../src/dotty/tools/dotc/parsing/Parsers.scala     | 14 +++++++++++++-
 tests/pos/i21768.scala                             | 12 ++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i21768.scala

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index cd727ba8ac72..926e748b85c7 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -1010,13 +1010,25 @@ object Parsers {
       skipParams()
       lookahead.isColon
       && {
+        lookahead.nextToken()
         !sourceVersion.isAtLeast(`3.6`)
         || { // in the new given syntax, a `:` at EOL after an identifier represents a single identifier given
              // Example:
              //    given C:
              //      def f = ...
-          lookahead.nextToken()
           !lookahead.isAfterLineEnd
+        } || {
+            // Support for for pre-3.6 syntax where type is put on the next line
+            // Examples:
+            //     given namedGiven:
+            //       X[T] with {}
+            //     given otherGiven:
+            //       X[T] = new X[T]{}
+          lookahead.isIdent && {
+            lookahead.nextToken()
+            skipParams()
+            lookahead.token == WITH || lookahead.token == EQUALS
+          }
         }
       }
 
diff --git a/tests/pos/i21768.scala b/tests/pos/i21768.scala
new file mode 100644
index 000000000000..85066d0cb8a6
--- /dev/null
+++ b/tests/pos/i21768.scala
@@ -0,0 +1,12 @@
+
+trait Foo[T]:
+  def foo(v: T): Unit
+
+given myFooOfInt:
+  Foo[Int] with
+  def foo(v: Int): Unit = ???
+
+given myFooOfLong:
+  Foo[Long] = new Foo[Long] {
+    def foo(v: Long): Unit = ???
+  }

From a87a18912002a2d29439b83dfe1f61270c892026 Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Sun, 17 Nov 2024 22:43:46 +0100
Subject: [PATCH 2/2] Delay `.nextToken` computation as per review comment

---
 compiler/src/dotty/tools/dotc/parsing/Parsers.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 926e748b85c7..7a55690dcc21 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -1010,12 +1010,12 @@ object Parsers {
       skipParams()
       lookahead.isColon
       && {
-        lookahead.nextToken()
         !sourceVersion.isAtLeast(`3.6`)
         || { // in the new given syntax, a `:` at EOL after an identifier represents a single identifier given
              // Example:
              //    given C:
              //      def f = ...
+          lookahead.nextToken()
           !lookahead.isAfterLineEnd
         } || {
             // Support for for pre-3.6 syntax where type is put on the next line