ExitDetector: Don't short-circuit return on non-exiting case statements

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index ca02438d7ee4fb47d33baf18f7a934a0e4910bd9..1ae2befb8d806ae8dfcff9d897935c8819c1b7b0 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -3755,6 +3755,7 @@ class ExitDetector extends GeneralizingAstVisitor<bool> {
     _enclosingBlockContainsBreak = false;
     try {
       bool hasDefault = false;
+      bool hasNonExitingCase;

[Brian Wilkerson, 2016/06/14 16:27:14]

nit: While not strictly necessary, I'd prefer all 'bool' valued variables be
initialized to a non-null value unless there's a really good reason not to.

[srawlins, 2016/06/14 18:28:17]

Done.

       List<SwitchMember> members = node.members;
       for (int i = 0; i < members.length; i++) {
         SwitchMember switchMember = members[i];
@@ -3763,16 +3764,20 @@ class ExitDetector extends GeneralizingAstVisitor<bool> {
           // If this is the last member and there are no statements, return

[Brian Wilkerson, 2016/06/14 16:27:15]

nit: the code below no longer returns

[srawlins, 2016/06/14 18:28:17]

Done.

           // false
           if (switchMember.statements.isEmpty && i + 1 == members.length) {
-            return false;
+            hasNonExitingCase = true;
+            continue;
           }
         }
         // For switch members with no statements, don't visit the children,
         // otherwise, return false if no return is found in the children

[Brian Wilkerson, 2016/06/14 16:27:15]

nit: the code below no longer returns

[srawlins, 2016/06/14 18:28:17]

Done.

         // statements.
         if (!switchMember.statements.isEmpty && !switchMember.accept(this)) {
-          return false;
+          hasNonExitingCase = true;
         }
       }
+      if (hasNonExitingCase) {
+        return false;
+      }
       // As all cases exit, return whether that list includes `default`.
       return hasDefault;
     } finally {