RedundantBraces: fix removing blocks

We continue removing blocks nested within another block, assuming that
at least one outer block is preserved if necessary.

Therefore, before removing an outer block, make sure it doesn't contain
a deeply nested multi-stat expression.

scalafmt-core/shared/src/main/scala/org/scalafmt/rewrite/RedundantBraces.scala

@@ -661,8 +661,7 @@ class RedundantBraces(implicit val ftoks: FormatTokens)
       // can allow if: no ".foo", no "with B", or has braces
       !b.parent.is[Term.Select] || t.templ.inits.lengthCompare(1) <= 0 ||
       t.templ.body.stats.nonEmpty || t.tokens.last.is[T.RightBrace]
-    case _: Term => true
-    case _ => false
+    case _ => isTreeSingleExpr(s)
   }
 
   private def okToRemoveBlockWithinApply(b: Term.Block)(implicit

scalafmt-tests/shared/src/test/resources/rewrite/RedundantBraces2.stat

@@ -768,16 +768,10 @@ object a {
   }
 }
 >>>
-test does not parse: [dialect scala213] illegal start of simple expression
 object a {
-  def foo =
-    val len = firstColumn + syntax.length; (len, len)
-    ^
-}
-====== full result: ======
-object a {
-  def foo =
+  def foo = {
     val len = firstColumn + syntax.length; (len, len)
+  }
 }
 <<< def body as nested block 2
 object a {
@@ -786,16 +780,10 @@ object a {
   }
 }
 >>>
-test does not parse: [dialect scala213] illegal start of simple expression
-object a {
-  def foo =
-    val len = firstColumn + syntax.length; (len, len)
-    ^
-}
-====== full result: ======
 object a {
-  def foo =
+  def foo = {
     val len = firstColumn + syntax.length; (len, len)
+  }
 }
 <<< def body as nested block 3
 object a {
@@ -804,14 +792,8 @@ object a {
   }
 }
 >>>
-test does not parse: [dialect scala213] illegal start of simple expression
 object a {
-  def foo =
-    val len = firstColumn + syntax.length; (len, len)
-    ^
-}
-====== full result: ======
-object a {
-  def foo =
+  def foo = {
     val len = firstColumn + syntax.length; (len, len)
+  }
 }

scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala

@@ -154,7 +154,7 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
     val explored = Debug.explored.get()
     logger.debug(s"Total explored: $explored")
     if (!onlyUnit && !onlyManual)
-      assertEquals(explored, 2519892, "total explored")
+      assertEquals(explored, 2520060, "total explored")
     val results = debugResults.result()
     // TODO(olafur) don't block printing out test results.
     // I don't want to deal with scalaz's Tasks :'(