Fix rebase breakage and add a test

Author: odersky

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1280,13 +1280,14 @@ object Parsers {
 
     def argumentStart(): Unit =
       colonAtEOLOpt()
-      if in.isScala2CompatMode && in.token == NEWLINE && in.next.token == LBRACE then
+      if migrateTo3 && in.token == NEWLINE && in.next.token == LBRACE then
         in.nextToken()
         if in.indentWidth(in.offset) == in.currentRegion.indentWidth then
-          in.errorOrMigrationWarning(
+          ctx.errorOrMigrationWarning(
             i"""This opening brace will start a new statement in Scala 3.
                |It needs to be indented to the right to keep being treated as
-               |an argument to the previous expression.${rewriteNotice()}""")
+               |an argument to the previous expression.${rewriteNotice()}""",
+            in.sourcePos())
           patch(source, Span(in.offset), "  ")
 
     def possibleTemplateStart(isNew: Boolean = false): Unit =

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -438,7 +438,7 @@ object Scanners {
     def isContinuingParens() =
       openParensTokens.contains(token)
       && !pastBlankLine
-      && !isScala2CompatMode
+      && !migrateTo3
       && !noindentSyntax
 
     /** The indentation width of the given offset */

tests/pos/newline-braces.scala

@@ -14,3 +14,10 @@ def f: Int => Int =
   { (x: Int) =>
     x + 1
   }
+
+val x =
+    true &&          // newline inserted here but skipped because of trailing &&
+    {
+      val xyz = true
+      xyz && false
+    }