[CSDiagnostics] Diagnose invalid optional unwrap via fixes

Detect and fix situations when (force) unwrap is used on
a non-optional type, this helps to diagnose invalid unwraps
precisely and provide fix-its.

Resolves: [SR-8977](https://bugs.swift.org/browse/SR-8977)
Resolves: rdar://problem/45218255

lib/Sema/CSDiagnostics.cpp

@@ -1226,3 +1226,17 @@ bool AutoClosureForwardingFailure::diagnoseAsError() {
       .fixItInsertAfter(argExpr->getEndLoc(), "()");
   return true;
 }
+
+bool NonOptionalUnwrapFailure::diagnoseAsError() {
+  auto *anchor = getAnchor();
+
+  auto diagnostic = diag::invalid_optional_chain;
+  if (isa<ForceValueExpr>(anchor))
+    diagnostic = diag::invalid_force_unwrap;
+
+  emitDiagnostic(anchor->getLoc(), diagnostic, BaseType)
+      .highlight(anchor->getSourceRange())
+      .fixItRemove(anchor->getEndLoc());
+
+  return true;
+}