From b3ac78fca13634aab203ae727f91b4a759f936b3 Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Wed, 9 Jun 2021 20:01:00 +0200
Subject: [PATCH] TyperState#commit: Flush reporter before committing

Flushing the reporter can force messages (apparently because of
`HideNonSensicalMessages#isHidden`) which can affect the TyperState
we're in the process of committing, so make sure that flushing happens
before committing to not trigger any assertion.

Fixes #12736
---
 compiler/src/dotty/tools/dotc/core/TyperState.scala | 2 +-
 tests/neg/i12736b.scala                             | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 tests/neg/i12736b.scala

diff --git a/compiler/src/dotty/tools/dotc/core/TyperState.scala b/compiler/src/dotty/tools/dotc/core/TyperState.scala
index 0f5ea0ac431d..2c41fc8f0231 100644
--- a/compiler/src/dotty/tools/dotc/core/TyperState.scala
+++ b/compiler/src/dotty/tools/dotc/core/TyperState.scala
@@ -140,6 +140,7 @@ class TyperState() {
     Stats.record("typerState.commit")
     assert(isCommittable, s"$this is not committable")
     assert(!isCommitted, s"$this is already committed")
+    reporter.flush()
     setCommittable(false)
     val targetState = ctx.typerState
     assert(!targetState.isCommitted, s"Attempt to commit $this into already committed $targetState")
@@ -152,7 +153,6 @@ class TyperState() {
       else
         targetState.mergeConstraintWith(this)
     targetState.gc()
-    reporter.flush()
     isCommitted = true
   }
 
diff --git a/tests/neg/i12736b.scala b/tests/neg/i12736b.scala
new file mode 100644
index 000000000000..c7db2f7a92ea
--- /dev/null
+++ b/tests/neg/i12736b.scala
@@ -0,0 +1,6 @@
+object Test {
+  def apply[S](r: Any)(using DoesntExist): Any = r // error
+
+  def test(o: Option[Any]) =
+    o.map(x => Test(doesntExist, x)) // error
+}