Adapt analyzer to new warnings around switch-case fallthrough.

Fixes issue #27664.
BUG= http://dartbug.com/27664
R=brianwilkerson@google.com

Review URL: https://codereview.chromium.org/2446093003 .

pkg/analyzer/lib/src/error/codes.dart

@@ -3279,14 +3279,14 @@ class StaticWarningCode extends ErrorCode {
 
   /**
    * 13.9 Switch: It is a static warning if the last statement of the statement
-   * sequence <i>s<sub>k</sub></i> is not a break, continue, return or throw
-   * statement.
+   * sequence <i>s<sub>k</sub></i> is not a break, continue, rethrow, return
+   * or throw statement.
    */
   static const StaticWarningCode CASE_BLOCK_NOT_TERMINATED =
       const StaticWarningCode(
           'CASE_BLOCK_NOT_TERMINATED',
           "The last statement of the 'case' should be 'break', 'continue', "
-          "'return' or 'throw'.",
+          "'rethrow', 'return' or 'throw'.",
           "Try adding one of the required statements.");
 
   /**

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

@@ -2596,7 +2596,10 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
       }
       // no other switch member after this one
     } else {
-      Statement statement = statements[statements.length - 1];
+      Statement statement = statements.last;
+      if (statement is Block && statement.statements.isNotEmpty) {
+        statement = statement.statements.last;
+      }
       // terminated with statement
       if (statement is BreakStatement ||
           statement is ContinueStatement ||
@@ -2606,7 +2609,8 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
       // terminated with 'throw' expression
       if (statement is ExpressionStatement) {
         Expression expression = statement.expression;
-        if (expression is ThrowExpression) {
+        if (expression is ThrowExpression ||
+            expression is RethrowExpression) {
           return;
         }
       }
@@ -2618,7 +2622,7 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
 
   /**
    * Verify that the switch cases in the given switch [statement] are terminated
-   * with 'break', 'continue', 'return' or 'throw'.
+   * with 'break', 'continue', 'rethrow', 'return' or 'throw'.
    *
    * See [StaticWarningCode.CASE_BLOCK_NOT_TERMINATED].
    */

tests/language/language_analyzer2.status

@@ -3,10 +3,6 @@
 # BSD-style license that can be found in the LICENSE file.
 
 [ $compiler == dart2analyzer ]
-# Issue #27664
-switch_case_warn_test/none: StaticWarning
-switch_case_warn_test/retnon: StaticWarning
-switch_case_warn_test/retval: StaticWarning
 
 regress_26668_test: Fail # Issue 26678
 regress_27617_test/1: MissingCompileTimeError

tests/language/switch_case_warn_test.dart

@@ -11,7 +11,7 @@
 void testSwitch(int x) {
   // Catch all control flow leaving the switch.
   // Run switch in catch clause to check rethrow.
-  try {
+  TRY: try {
     throw x;
   } catch (x) {
     // Add loop as break/continue target.
@@ -92,14 +92,16 @@ void testSwitch(int x) {
     } while (false);
   } finally {
     // Catch all control flow leaving the switch and ignore it.
-    return;
+    // Use break instead of return to avoid warning for `return` and `return e`
+    // in same function.
+    break TRY;
   }
 }
 
 // All these switch cases should cause warnings.
 void testSwitchWarn(x) {
   // Catch all control flow from the switch and ignore it.
-  try {
+  TRY: try {
     throw 0;
   } catch (e) {
     // Wrap in loop as target for continue/break.
@@ -183,7 +185,9 @@ void testSwitchWarn(x) {
     } while (false);
   } finally {
     // Catch all control flow leaving the switch and ignore it.
-    return;
+    // Use break instead of return to avoid warning for `return` and `return e`
+    // in same function.
+    break TRY;
   }
 }