When adding '!' in fix-it, make sure that it doesn't fall into the

optional evaluation context that produced the optional.

<rdar://problem/20377684> Oscillating fixit for optional chain calling method that returns non-optional

Swift SVN r28212

lib/Sema/CSApply.cpp

@@ -5905,7 +5905,8 @@ Expr *ConstraintSystem::applySolution(Solution &solution, Expr *expr,
         auto diag = TC.diagnose(affected->getLoc(),
                                 diag::missing_unwrap_optional, type);
         bool parensNeeded = (getInfixData(DC, affected).getPrecedence() <
-                             IntrinsicPrecedences::PostfixUnaryExpr);
+                                IntrinsicPrecedences::PostfixUnaryExpr) ||
+                            isa<OptionalEvaluationExpr>(affected);
         if (parensNeeded) {
           diag.fixItInsert(affected->getStartLoc(), "(")
               .fixItInsertAfter(affected->getEndLoc(), ")!");

test/Constraints/fixes.swift

@@ -7,6 +7,7 @@ func f3(Int...) -> Int { }
 class A { }
 class B : A { 
   func iAmAB() {}
+  func createB() -> B { return B() }
 }
 
 func f4() -> B { }
@@ -52,6 +53,11 @@ func forgotOptionalBang(a: A, obj: AnyObject) {
 
   var a = A(), b = B()
   b = a as? B  // expected-error{{value of optional type 'B?' not unwrapped; did you mean to use '!' or '?'?}}{{7-7=(}}{{14-14=)!}}
+
+  // rdar://problem/20377684 -- take care that the '!' doesn't fall into an
+  // optional evaluation context
+  let bo: B? = b
+  let b2: B = bo?.createB() // expected-error{{value of optional type 'B?' not unwrapped; did you mean to use '!' or '?'?}}{{15-15=(}}{{28-28=)!}}
 }
 
 func forgotAnyObjectBang(obj: AnyObject) {