From 541a3487ce92043a6ceff1dc5e9484206409a561 Mon Sep 17 00:00:00 2001
From: Tom Grigg <tomegrigg@gmail.com>
Date: Tue, 15 Feb 2022 14:49:23 -0800
Subject: [PATCH] Avoid stale import context during REPL parsing

---
 .../src/dotty/tools/repl/ReplDriver.scala     | 11 +++++++++-
 .../dotty/tools/repl/ReplCompilerTests.scala  | 21 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/repl/ReplDriver.scala b/compiler/src/dotty/tools/repl/ReplDriver.scala
index 5eef023c1fc2..f69a7ca142fb 100644
--- a/compiler/src/dotty/tools/repl/ReplDriver.scala
+++ b/compiler/src/dotty/tools/repl/ReplDriver.scala
@@ -254,6 +254,12 @@ class ReplDriver(settings: Array[String],
     def extractTopLevelImports(ctx: Context): List[tpd.Import] =
       unfusedPhases(using ctx).collectFirst { case phase: CollectTopLevelImports => phase.imports }.get
 
+    def contextWithNewImports(ctx: Context, imports: List[tpd.Import]): Context =
+      if imports.isEmpty then ctx
+      else
+        imports.foldLeft(ctx.fresh.setNewScope)((ctx, imp) =>
+          ctx.importContext(imp, imp.symbol(using ctx)))
+
     implicit val state = {
       val state0 = newRun(istate, parsed.reporter)
       state0.copy(context = state0.context.withSource(parsed.source))
@@ -269,7 +275,10 @@ class ReplDriver(settings: Array[String],
             var allImports = newState.imports
             if (newImports.nonEmpty)
               allImports += (newState.objectIndex -> newImports)
-            val newStateWithImports = newState.copy(imports = allImports)
+            val newStateWithImports = newState.copy(
+              imports = allImports,
+              context = contextWithNewImports(newState.context, newImports)
+            )
 
             val warnings = newState.context.reporter
               .removeBufferedMessages(using newState.context)
diff --git a/compiler/test/dotty/tools/repl/ReplCompilerTests.scala b/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
index 3c70f838caa3..c02552aac83c 100644
--- a/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
+++ b/compiler/test/dotty/tools/repl/ReplCompilerTests.scala
@@ -241,6 +241,27 @@ class ReplCompilerTests extends ReplTest:
     assertEquals(List("// defined class C"), lines())
   }
 
+  @Test def i14491 =
+    initially {
+      run("import language.experimental.fewerBraces")
+    } andThen {
+      run("""|val x = Seq(7,8,9).apply:
+             |  1
+             |""".stripMargin)
+      assertEquals("val x: Int = 8", storedOutput().trim)
+    }
+    initially {
+      run("""|import language.experimental.fewerBraces
+             |import language.experimental.fewerBraces as _
+             |""".stripMargin)
+    } andThen {
+      run("""|val x = Seq(7,8,9).apply:
+             |  1
+             |""".stripMargin)
+      assert("expected error if fewerBraces is unimported",
+        lines().exists(_.contains("missing arguments for method apply")))
+    }
+
 object ReplCompilerTests:
 
   private val pattern = Pattern.compile("\\r[\\n]?|\\n");