Disallow `continue` referring to a non-IterationStatement. Fix #287

Simplifies handling of labels (their definition/references can be easily
figured out at parse time, no need to do it in `figure_out_scope`).

4 files changed, 34 insertions, 48 deletions

diff --git a/lib/ast.js b/lib/ast.js
index b8e89f23..e51cdd02 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -197,6 +197,10 @@ var AST_LabeledStatement = DEFNODE("LabeledStatement", "label", {
     }
 }, AST_StatementWithBody);
 
+var AST_IterationStatement = DEFNODE("Loop", null, {
+    $documentation: "Internal class.  All loops inherit from it."
+}, AST_StatementWithBody);
+
 var AST_DWLoop = DEFNODE("DWLoop", "condition", {
     $documentation: "Base class for do/while statements",
     $propdoc: {
@@ -208,7 +212,7 @@ var AST_DWLoop = DEFNODE("DWLoop", "condition", {
             this.body._walk(visitor);
         });
     }
-}, AST_StatementWithBody);
+}, AST_IterationStatement);
 
 var AST_Do = DEFNODE("Do", null, {
     $documentation: "A `do` statement",
@@ -233,7 +237,7 @@ var AST_For = DEFNODE("For", "init condition step", {
             this.body._walk(visitor);
         });
     }
-}, AST_StatementWithBody);
+}, AST_IterationStatement);
 
 var AST_ForIn = DEFNODE("ForIn", "init name object", {
     $documentation: "A `for ... in` statement",
@@ -249,7 +253,7 @@ var AST_ForIn = DEFNODE("ForIn", "init name object", {
             this.body._walk(visitor);
         });
     }
-}, AST_StatementWithBody);
+}, AST_IterationStatement);
 
 var AST_With = DEFNODE("With", "expression", {
     $documentation: "A `with` statement",
@@ -821,7 +825,11 @@ var AST_SymbolCatch = DEFNODE("SymbolCatch", null, {
 var AST_Label = DEFNODE("Label", "references", {
     $documentation: "Symbol naming a label (declaration)",
     $propdoc: {
-        references: "[AST_LabelRef*] a list of nodes referring to this label"
+        references: "[AST_LoopControl*] a list of nodes referring to this label"
+    },
+    initialize: function() {
+        this.references = [];
+        this.thedef = this;
     }
 }, AST_Symbol);
 
diff --git a/lib/compress.js b/lib/compress.js
index 8d936bac..0d2053e7 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -324,7 +324,7 @@ merge(Compressor.prototype, {
                                || (ab instanceof AST_Continue && self === loop_body(lct))
                                || (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
                         if (ab.label) {
-                            remove(ab.label.thedef.references, ab.label);
+                            remove(ab.label.thedef.references, ab);
                         }
                         CHANGED = true;
                         var body = as_statement_array(stat.body).slice(0, -1);
@@ -346,7 +346,7 @@ merge(Compressor.prototype, {
                                || (ab instanceof AST_Continue && self === loop_body(lct))
                                || (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
                         if (ab.label) {
-                            remove(ab.label.thedef.references, ab.label);
+                            remove(ab.label.thedef.references, ab);
                         }
                         CHANGED = true;
                         stat = stat.clone();
@@ -385,7 +385,7 @@ merge(Compressor.prototype, {
                              && loop_body(lct) === self) || (stat instanceof AST_Continue
                                                              && loop_body(lct) === self)) {
                             if (stat.label) {
-                                remove(stat.label.thedef.references, stat.label);
+                                remove(stat.label.thedef.references, stat);
                             }
                         } else {
                             a.push(stat);
diff --git a/lib/parse.js b/lib/parse.js
index abd4d7b7..6946d93c 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -828,6 +828,18 @@ function parse($TEXT, options) {
         S.labels.push(label);
         var stat = statement();
         S.labels.pop();
+        if (!(stat instanceof AST_IterationStatement)) {
+            // check for `continue` that refers to this label.
+            // those should be reported as syntax errors.
+            // https://github.com/mishoo/UglifyJS2/issues/287
+            label.references.forEach(function(ref){
+                if (ref instanceof AST_Continue) {
+                    ref = ref.label.start;
+                    croak("Continue label `" + label.name + "` refers to non-loop statement.",
+                          ref.line, ref.col, ref.pos);
+                }
+            });
+        }
         return new AST_LabeledStatement({ body: stat, label: label });
     };
 
@@ -836,18 +848,22 @@ function parse($TEXT, options) {
     };
 
     function break_cont(type) {
-        var label = null;
+        var label = null, ldef;
         if (!can_insert_semicolon()) {
             label = as_symbol(AST_LabelRef, true);
         }
         if (label != null) {
-            if (!find_if(function(l){ return l.name == label.name }, S.labels))
+            ldef = find_if(function(l){ return l.name == label.name }, S.labels);
+            if (!ldef)
                 croak("Undefined label " + label.name);
+            label.thedef = ldef;
         }
         else if (S.in_loop == 0)
             croak(type.TYPE + " not inside a loop or switch");
         semicolon();
-        return new type({ label: label });
+        var stat = new type({ label: label });
+        if (ldef) ldef.references.push(stat);
+        return stat;
     };
 
     function for_() {
diff --git a/lib/scope.js b/lib/scope.js
index d15cec75..8fc1ce0b 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -82,18 +82,14 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
     // pass 1: setup scope chaining and handle definitions
     var self = this;
     var scope = self.parent_scope = null;
-    var labels = new Dictionary();
     var nesting = 0;
     var tw = new TreeWalker(function(node, descend){
         if (node instanceof AST_Scope) {
             node.init_scope_vars(nesting);
             var save_scope = node.parent_scope = scope;
-            var save_labels = labels;
             ++nesting;
             scope = node;
-            labels = new Dictionary();
             descend();
-            labels = save_labels;
             scope = save_scope;
             --nesting;
             return true;        // don't descend again in TreeWalker
@@ -108,22 +104,9 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
                 s.uses_with = true;
             return;
         }
-        if (node instanceof AST_LabeledStatement) {
-            var l = node.label;
-            if (labels.has(l.name))
-                throw new Error(string_template("Label {name} defined twice", l));
-            labels.set(l.name, l);
-            descend();
-            labels.del(l.name);
-            return true;        // no descend again
-        }
         if (node instanceof AST_Symbol) {
             node.scope = scope;
         }
-        if (node instanceof AST_Label) {
-            node.thedef = node;
-            node.init_scope_vars();
-        }
         if (node instanceof AST_SymbolLambda) {
             scope.def_function(node);
         }
@@ -150,15 +133,6 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
             // identifier in the enclosing scope)
             scope.def_variable(node);
         }
-        if (node instanceof AST_LabelRef) {
-            var sym = labels.get(node.name);
-            if (!sym) throw new Error(string_template("Undefined label {name} [{line},{col}]", {
-                name: node.name,
-                line: node.start.line,
-                col: node.start.col
-            }));
-            node.thedef = sym;
-        }
     });
     self.walk(tw);
 
@@ -173,10 +147,6 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
             func = prev_func;
             return true;
         }
-        if (node instanceof AST_LabelRef) {
-            node.reference();
-            return true;
-        }
         if (node instanceof AST_SymbolRef) {
             var name = node.name;
             var sym = node.scope.find_variable(name);
@@ -241,14 +211,6 @@ AST_SymbolRef.DEFMETHOD("reference", function() {
     this.frame = this.scope.nesting - def.scope.nesting;
 });
 
-AST_Label.DEFMETHOD("init_scope_vars", function(){
-    this.references = [];
-});
-
-AST_LabelRef.DEFMETHOD("reference", function(){
-    this.thedef.references.push(this);
-});
-
 AST_Scope.DEFMETHOD("find_variable", function(name){
     if (name instanceof AST_Symbol) name = name.name;
     return this.variables.get(name)