[Sema] Fix compiler crash when pattern matching optional enum

TypeCheckPattern was able to take the path checking if `Optional.None`
should be renamed to lowercase `Optional.none` and if this wasn't
necessary still failed but without generating a diagnostic.
Now it always provides a diagnostic when failing.

This fixes SR-2057.

Author: ahoppen

lib/Sema/TypeCheckPattern.cpp

@@ -1453,8 +1453,8 @@ bool TypeChecker::coercePatternToType(Pattern *&P, DeclContext *dc, Type type,
                           /*special kind*/0, Rename.str())
                 .fixItReplace(EEP->getLoc(), Rename.str());
 
+              return true;
             }
-            return true;
           }
 
           diagnose(EEP->getLoc(), diag::enum_element_pattern_member_not_found,

test/Constraints/patterns.swift

@@ -222,3 +222,13 @@ func ugly(_ a: A<EE>) {
     }
   }
 }
+
+// SR-2057
+
+enum SR2057 {
+  case foo
+}
+
+let sr2057: SR2057? = nil
+if case .foo = sr2057 { } // expected-error{{enum case 'foo' not found in type 'SR2057?'}}
+