From 349d75a31829cc5a60880416026d3c5c4f81ae86 Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Mon, 9 Aug 2021 14:17:42 +0200
Subject: [PATCH] Allow `case` in pattern bindings even without -Xsource:3

In #9558 (which shipped with 2.13.6) we added support for `case` bindings
under -Xsource:3. Since this parser change does not break any existing
code and since IntelliJ and scalameta/metals now understand this syntax
in Scala 2 code, it should be safe to enable it by default to further
ease cross-compilation between Scala 2 and 3.
---
 .../scala/tools/nsc/ast/parser/Parsers.scala  |  4 +---
 .../neg/for-comprehension-case-future.check   |  7 ------
 .../neg/for-comprehension-case-future.scala   | 24 -------------------
 test/files/neg/for-comprehension-case.check   | 14 ++++-------
 test/files/neg/for-comprehension-case.scala   | 16 +++++++++----
 5 files changed, 17 insertions(+), 48 deletions(-)
 delete mode 100644 test/files/neg/for-comprehension-case-future.check
 delete mode 100644 test/files/neg/for-comprehension-case-future.scala

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index adc577f54c86..472696ab8118 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -1999,10 +1999,8 @@ self =>
     def generator(eqOK: Boolean, allowNestedIf: Boolean = true): List[Tree] = {
       val start  = in.offset
       val hasCase = in.token == CASE
-      if (hasCase) {
-        if (!currentRun.isScala3) syntaxError(in.offset, s"`case` keyword in for comprehension requires the -Xsource:3 flag.")
+      if (hasCase)
         in.skipCASE()
-      }
 
       val hasVal = in.token == VAL
       if (hasVal)
diff --git a/test/files/neg/for-comprehension-case-future.check b/test/files/neg/for-comprehension-case-future.check
deleted file mode 100644
index 9ce9a9456882..000000000000
--- a/test/files/neg/for-comprehension-case-future.check
+++ /dev/null
@@ -1,7 +0,0 @@
-for-comprehension-case-future.scala:22: error: '<-' expected but '=' found.
-      case y = x + 1
-             ^
-for-comprehension-case-future.scala:23: error: illegal start of simple expression
-    } yield x + y
-    ^
-2 errors
diff --git a/test/files/neg/for-comprehension-case-future.scala b/test/files/neg/for-comprehension-case-future.scala
deleted file mode 100644
index 05602e537759..000000000000
--- a/test/files/neg/for-comprehension-case-future.scala
+++ /dev/null
@@ -1,24 +0,0 @@
-// scalac: -Xsource:3
-//
-class A {
-  // ok
-  val a =
-    for {
-      case Some(x) <- List(Some(1), None)
-      y = x + 1
-    } yield x + y
-
-  // ok
-  val b =
-    for {
-      Some(x) <- List(Some(1), None)
-      Some(y) <- List(None, Some(2))
-    } yield x+y
-
-  // fail
-  val c =
-    for {
-      case Some(x) <- List(Some(1), None)
-      case y = x + 1
-    } yield x + y
-}
diff --git a/test/files/neg/for-comprehension-case.check b/test/files/neg/for-comprehension-case.check
index 2e86e5d367b0..549e4943e344 100644
--- a/test/files/neg/for-comprehension-case.check
+++ b/test/files/neg/for-comprehension-case.check
@@ -1,13 +1,7 @@
-for-comprehension-case.scala:5: error: `case` keyword in for comprehension requires the -Xsource:3 flag.
-      case Some(x) <- List(Some(1), None)
-      ^
-for-comprehension-case.scala:12: error: `case` keyword in for comprehension requires the -Xsource:3 flag.
-      case y = x + 1
-      ^
-for-comprehension-case.scala:12: error: '<-' expected but '=' found.
+for-comprehension-case.scala:20: error: '<-' expected but '=' found.
       case y = x + 1
              ^
-for-comprehension-case.scala:13: error: illegal start of simple expression
-    } yield x+y
+for-comprehension-case.scala:21: error: illegal start of simple expression
+    } yield x + y
     ^
-4 errors
+2 errors
diff --git a/test/files/neg/for-comprehension-case.scala b/test/files/neg/for-comprehension-case.scala
index 55e8d44a40e3..d6b14eb91a90 100644
--- a/test/files/neg/for-comprehension-case.scala
+++ b/test/files/neg/for-comprehension-case.scala
@@ -1,14 +1,22 @@
 class A {
-  // fail
+  // ok
   val a =
     for {
       case Some(x) <- List(Some(1), None)
-    } yield x
+      y = x + 1
+    } yield x + y
 
-  // fail
+  // ok
   val b =
     for {
       Some(x) <- List(Some(1), None)
-      case y = x + 1
+      Some(y) <- List(None, Some(2))
     } yield x+y
+
+  // fail
+  val c =
+    for {
+      case Some(x) <- List(Some(1), None)
+      case y = x + 1
+    } yield x + y
 }