fix unused crashes (#1599)

- `AST_DefaultAssign` on `keep_fargs`
- `AST_Expansion on` `keep_fargs`
- `AST_Destructuring` on top-level declarations without `toplevel`

lib/ast.js

@@ -814,9 +814,6 @@ var AST_VarDef = DEFNODE("VarDef", "name value", {
         name: "[AST_SymbolVar|AST_SymbolConst|AST_Destructuring] name of the variable",
         value: "[AST_Node?] initializer, or null of there's no initializer"
     },
-    is_destructuring: function() {
-        return this.name instanceof AST_Destructuring;
-    },
     _walk: function(visitor) {
         return visitor._visit(this, function(){
             this.name._walk(visitor);

lib/compress.js

@@ -1789,14 +1789,18 @@ merge(Compressor.prototype, {
                     if (node instanceof AST_Definitions && scope === self) {
                         node.definitions.forEach(function(def){
                             if (!drop_vars) {
-                                var node_def = def.name.definition();
-                                if (node_def.global && !(node_def.id in in_use_ids)) {
-                                    in_use_ids[node_def.id] = true;
-                                    in_use.push(node_def);
-                                }
+                                def.name.walk(new TreeWalker(function(node) {
+                                    if (node instanceof AST_SymbolDeclaration) {
+                                        var def = node.definition();
+                                        if (def.global && !(def.id in in_use_ids)) {
+                                            in_use_ids[def.id] = true;
+                                            in_use.push(def);
+                                        }
+                                    }
+                                }));
                             }
                             if (def.value) {
-                                if (def.is_destructuring()) {
+                                if (def.name instanceof AST_Destructuring) {
                                     var destructuring_cache = destructuring_value;
                                     destructuring_value = def.value;
                                     in_definition = true;
@@ -1907,7 +1911,10 @@ merge(Compressor.prototype, {
                         for (var a = node.argnames, i = a.length; --i >= 0;) {
                             var sym = a[i];
                             if (sym instanceof AST_Expansion) {
-                                sym = sym.symbol;
+                                sym = sym.expression;
+                            }
+                            if (sym instanceof AST_DefaultAssign) {
+                                sym = sym.left;
                             }
                             // Do not drop destructuring arguments.
                             // They constitute a type assertion, so dropping
@@ -1947,7 +1954,7 @@ merge(Compressor.prototype, {
                     if (node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
                         var def = node.definitions.filter(function(def){
                             if (def.value) def.value = def.value.transform(tt);
-                            if (def.is_destructuring()) return true;
+                            if (def.name instanceof AST_Destructuring) return true;
                             if (def.name.definition().id in in_use_ids) return true;
                             if (!drop_vars && def.name.definition().global) return true;
 
@@ -2090,7 +2097,7 @@ merge(Compressor.prototype, {
                         }
                         if (node instanceof AST_Var && hoist_vars) {
                             node.definitions.forEach(function(def){
-                                if (def.is_destructuring()) { return; }
+                                if (def.name instanceof AST_Destructuring) return;
                                 vars.set(def.name.name, def);
                                 ++vars_found;
                             });
@@ -2698,7 +2705,7 @@ merge(Compressor.prototype, {
 
     AST_Definitions.DEFMETHOD("to_assignments", function(){
         var assignments = this.definitions.reduce(function(a, def){
-            if (def.value && !def.is_destructuring()) {
+            if (def.value && !(def.name instanceof AST_Destructuring)) {
                 var name = make_node(AST_SymbolRef, def.name, def.name);
                 a.push(make_node(AST_Assign, def, {
                     operator : "=",

test/compress/destructuring.js

@@ -293,3 +293,17 @@ reduce_vars: {
         for ([x,y] in pairs);
     }
 }
+
+unused: {
+    options = {
+        unused: true,
+    }
+    input: {
+        let { foo: [, , ...a] } = { foo: [1, 2, 3, 4], bar: 5 };
+        console.log(a);
+    }
+    expect: {
+        let { foo: [, , ...a] } = { foo: [1, 2, 3, 4], bar: 5 };
+        console.log(a);
+    }
+}

test/compress/harmony.js

@@ -286,3 +286,37 @@ fat_arrow_as_param: {
     }
     expect_exact: "foo(x=>x);foo(x=>x,y=>y);foo(x=>(x,x));foo(x=>(x,x),y=>(y,y));"
 }
+
+default_assign: {
+    options = {
+        keep_fargs: false,
+        unused: true,
+    }
+    input: {
+        function f(a, b = 3) {
+            console.log(a);
+        }
+    }
+    expect: {
+        function f(a) {
+            console.log(a);
+        }
+    }
+}
+
+expansion: {
+    options = {
+        keep_fargs: false,
+        unused: true,
+    }
+    input: {
+        function f(a, ...b) {
+            console.log(a);
+        }
+    }
+    expect: {
+        function f(a) {
+            console.log(a);
+        }
+    }
+}