Fix breaking before is keyword causing illegal code

Summary:
This should resolve #315

Tried to avoid changing code in too many places by looking at the parent.

Reviewed By: davidtorosyan

Differential Revision: D36783125

fbshipit-source-id: 54fcbdc7372f9147925b2746aa73e61fc06346d3

core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt

@@ -51,6 +51,7 @@ import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtCollectionLiteralExpression
 import org.jetbrains.kotlin.psi.KtConstantExpression
 import org.jetbrains.kotlin.psi.KtConstructorDelegationCall
+import org.jetbrains.kotlin.psi.KtContainerNode
 import org.jetbrains.kotlin.psi.KtContinueExpression
 import org.jetbrains.kotlin.psi.KtDelegatedSuperTypeEntry
 import org.jetbrains.kotlin.psi.KtDestructuringDeclaration
@@ -2169,7 +2170,14 @@ class KotlinInputAstVisitor(
     if (openGroupBeforeLeft) builder.open(ZERO)
     visit(expression.leftHandSide)
     if (!openGroupBeforeLeft) builder.open(ZERO)
-    builder.breakOp(Doc.FillMode.UNIFIED, " ", expressionBreakIndent)
+    val parent = expression.parent
+    if (parent is KtValueArgument ||
+        parent is KtParenthesizedExpression ||
+        parent is KtContainerNode) {
+      builder.breakOp(Doc.FillMode.UNIFIED, " ", expressionBreakIndent)
+    } else {
+      builder.space()
+    }
     visit(expression.operationReference)
     builder.breakOp(Doc.FillMode.INDEPENDENT, " ", expressionBreakIndent)
     builder.block(expressionBreakIndent) { visit(expression.typeReference) }

core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt

@@ -3236,7 +3236,13 @@ class FormatterTest {
       |  println(
       |      a is Int &&
       |          b is String)
+      |  l.b?.s?.sOrNull() is
+      |      SomethingLongEnough
       |}
+      |
+      |val a =
+      |    l.sOrNull() is
+      |        SomethingLongEnough
       |""".trimMargin(),
           deduceMaxWidth = true)