always keep declarations found in unreachable code

a few more tests and some cleanups.

test/compress/conditionals.js

@@ -0,0 +1,74 @@
+ifs_1: {
+    options = {
+        conditionals: true
+    };
+    input: {
+        if (foo) bar();
+        if (!foo); else bar();
+        if (foo); else bar();
+        if (foo); else;
+    }
+    expect: {
+        foo&&bar();
+        foo&&bar();
+        foo||bar();
+        foo;
+    }
+}
+
+ifs_2: {
+    options = {
+        conditionals: true
+    };
+    input: {
+        if (foo) {
+            x();
+        } else if (bar) {
+            y();
+        } else if (baz) {
+            z();
+        }
+
+        if (foo) {
+            x();
+        } else if (bar) {
+            y();
+        } else if (baz) {
+            z();
+        } else {
+            t();
+        }
+    }
+    expect: {
+        foo ? x() : bar ? y() : baz && z();
+        foo ? x() : bar ? y() : baz ? z() : t();
+    }
+}
+
+ifs_3_should_warn: {
+    options = {
+        conditionals : true,
+        dead_code    : true,
+        evaluate     : true,
+        booleans     : true
+    };
+    input: {
+        if (x && !(x + "1") && y) { // 1
+            var qq;
+            foo();
+        } else {
+            bar();
+        }
+
+        if (x || !!(x + "1") || y) { // 2
+            foo();
+        } else {
+            var jj;
+            bar();
+        }
+    }
+    expect: {
+        var qq; bar();          // 1
+        var jj; foo();          // 2
+    }
+}

test/compress/dead-code.js

@@ -57,3 +57,33 @@ dead_code_2_should_warn: {
         }
     }
 }
+
+dead_code_constant_boolean_should_warn_more: {
+    options = {
+        dead_code    : true,
+        loops        : true,
+        booleans     : true,
+        conditionals : true,
+        evaluate     : true
+    };
+    input: {
+        while (!((foo && bar) || (x + "0"))) {
+            console.log("unreachable");
+            var foo;
+            function bar() {}
+        }
+        for (var x = 10; x && (y || x) && (!typeof x); ++x) {
+            asdf();
+            foo();
+            var moo;
+        }
+    }
+    expect: {
+        var foo;
+        function bar() {}
+        // nothing for the while
+        // as for the for, it should keep:
+        var x = 10;
+        var moo;
+    }
+}

test/run-tests.js

@@ -119,8 +119,10 @@ function parse_test(file) {
                     })
                 );
                 var stat = node.body;
-                if (stat instanceof U.AST_BlockStatement && stat.body.length == 1)
-                    stat = stat.body[0];
+                if (stat instanceof U.AST_BlockStatement) {
+                    if (stat.body.length == 1) stat = stat.body[0];
+                    else if (stat.body.length == 0) stat = new U.AST_EmptyStatement();
+                }
                 test[node.label.name] = stat;
                 return true;
             }