fallthrough should not execute case expression

Also enable switch statement fuzzing.

fixes #1680

lib/compress.js

@@ -2562,11 +2562,6 @@ merge(Compressor.prototype, {
             }
             for (; i < len && fallthrough; i++) {
                 branch = self.body[i];
-                if (branch instanceof AST_Case) {
-                    exact_match.body.push(make_node(AST_SimpleStatement, branch.expression, {
-                        body: branch.expression
-                    }));
-                }
                 exact_match.body = exact_match.body.concat(branch.body);
                 fallthrough = !aborts(exact_match);
             }

test/compress/switch.js

@@ -23,7 +23,6 @@ constant_switch_2: {
     }
     expect: {
         foo();
-        2;
         bar();
     }
 }
@@ -118,7 +117,6 @@ constant_switch_6: {
             x();
             if (foo) break OUT;
             y();
-            2;
             bar();
         }
     }
@@ -157,7 +155,6 @@ constant_switch_7: {
                 console.log(x);
             }
             y();
-            2;
             bar();
         }
     }
@@ -206,7 +203,6 @@ constant_switch_9: {
             x();
             for (;;) if (foo) break OUT;
             y();
-            2;
             bar();
             def();
         }
@@ -481,3 +477,44 @@ issue_1679: {
     }
     expect_stdout: true
 }
+
+issue_1680: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+    }
+    input: {
+        function f(x) {
+            console.log(x);
+            return x + 1;
+        }
+        switch (2) {
+          case f(0):
+          case f(1):
+            f(2);
+          case 2:
+          case f(3):
+          case f(4):
+            f(5);
+        }
+    }
+    expect: {
+        function f(x) {
+            console.log(x);
+            return x + 1;
+        }
+        switch (2) {
+          case f(0):
+          case f(1):
+            f(2);
+          case 2:
+            f(5);
+        }
+    }
+    expect_stdout: [
+        "0",
+        "1",
+        "2",
+        "5",
+    ]
+}

test/ufuzz.js

@@ -201,7 +201,6 @@ function createStatement(recurmax, canThrow, canBreak, canContinue) {
     case 6:
       return createExpression(recurmax) + ';';
     case 7:
-      return ';'; // TODO: disabled until some switch issues are resolved
       // note: case args are actual expressions
       // note: default does not _need_ to be last
       return 'switch (' + createExpression(recurmax) + ') { ' + createSwitchParts(recurmax, 4) + '}';