typedApply: Avoid using incorrect context in tryEither

Previously, the following code accidentally used the implicit Context
parameter of `typedApply`:

        tryEither {
          implicit ctx => typedOpAssign

Author: smarter

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -683,7 +683,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
      *
      *     { val xs = es; e' = e' + args }
      */
-    def typedOpAssign: Tree = track("typedOpAssign") {
+    def typedOpAssign(implicit ctx: Context): Tree = track("typedOpAssign") {
       val Apply(Select(lhs, name), rhss) = tree
       val lhs1 = typedExpr(lhs)
       val liftedDefs = new mutable.ListBuffer[Tree]

tests/repl/imports.check

@@ -11,7 +11,7 @@ scala> buf += xs
 11 |buf += xs
    |       ^^
    |       found:    scala.collection.immutable.List[Int](o.xs)
-   |       required: String
+   |       required: Int
    |       
 scala> buf ++= xs
 val res1: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3)