fix for-in/of regression with let or const loop variable (#2840)

fixes #2835

lib/compress.js

@@ -1759,7 +1759,7 @@ merge(Compressor.prototype, {
             var stat = null;
             for (var i = 0, len = block.body.length; i < len; i++) {
                 var line = block.body[i];
-                if (line instanceof AST_Definitions && declarations_only(line)) {
+                if (line instanceof AST_Var && declarations_only(line)) {
                     decls.push(line);
                 } else if (stat) {
                     return false;
@@ -1803,7 +1803,9 @@ merge(Compressor.prototype, {
                             }
                         }
                     } else if (stat instanceof AST_ForIn) {
-                        stat.object = cons_seq(stat.object);
+                        if (!(stat.init instanceof AST_Const) && !(stat.init instanceof AST_Let)) {
+                            stat.object = cons_seq(stat.object);
+                        }
                     } else if (stat instanceof AST_If) {
                         stat.condition = cons_seq(stat.condition);
                     } else if (stat instanceof AST_Switch) {

test/compress/issue-1466.js

@@ -38,6 +38,7 @@ same_variable_in_multiple_for_loop: {
         }
     }
     expect_stdout: true
+    node_version: ">=6"
 }
 
 same_variable_in_multiple_forOf: {
@@ -79,7 +80,7 @@ same_variable_in_multiple_forOf: {
         }
     }
     expect_stdout: true
-    reminify: false // FIXME - regression https://github.com/mishoo/UglifyJS2/issues/2835
+    node_version: ">=6"
 }
 
 same_variable_in_multiple_forIn: {
@@ -121,7 +122,7 @@ same_variable_in_multiple_forIn: {
         }
     }
     expect_stdout: true
-    reminify: false // FIXME - regression https://github.com/mishoo/UglifyJS2/issues/2835
+    node_version: ">=6"
 }
 
 different_variable_in_multiple_for_loop: {
@@ -164,6 +165,7 @@ different_variable_in_multiple_for_loop: {
         }
     }
     expect_stdout: true
+    node_version: ">=6"
 }
 
 different_variable_in_multiple_forOf: {
@@ -205,6 +207,7 @@ different_variable_in_multiple_forOf: {
         }
     }
     expect_stdout: true
+    node_version: ">=6"
 }
 
 different_variable_in_multiple_forIn: {
@@ -246,6 +249,175 @@ different_variable_in_multiple_forIn: {
         }
     }
     expect_stdout: true
+    node_version: ">=6"
+}
+
+same_variable_in_multiple_forOf_sequences_let: {
+    options = {
+        hoist_funs: true,
+        dead_code: true,
+        conditionals: true,
+        comparisons: true,
+        evaluate: true,
+        booleans: true,
+        loops: true,
+        unused: true,
+        keep_fargs: true,
+        if_return: true,
+        join_vars: true,
+        sequences: true,
+        side_effects: true,
+        collapse_vars: true,
+    }
+    mangle = {}
+    input: {
+        var test = [ "a", "b", "c" ];
+        for (let tmp of test) {
+            console.log(tmp);
+            let dd;
+            dd = [ "e", "f", "g" ];
+            for (let tmp of dd) {
+                console.log(tmp);
+            }
+        }
+    }
+    expect: {
+        var test = [ "a", "b", "c" ];
+        for (let o of test) {
+            let e;
+            console.log(o), e = [ "e", "f", "g" ];
+            for (let o of e)
+                console.log(o);
+        }
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}
+
+same_variable_in_multiple_forOf_sequences_const: {
+    options = {
+        hoist_funs: true,
+        dead_code: true,
+        conditionals: true,
+        comparisons: true,
+        evaluate: true,
+        booleans: true,
+        loops: true,
+        unused: true,
+        keep_fargs: true,
+        if_return: true,
+        join_vars: true,
+        sequences: true,
+        side_effects: true,
+        collapse_vars: true,
+    }
+    mangle = {}
+    input: {
+        var test = [ "a", "b", "c" ];
+        for (const tmp of test) {
+            console.log(tmp);
+            let dd;
+            dd = [ "e", "f", "g" ];
+            for (const tmp of dd) {
+                console.log(tmp);
+            }
+        }
+    }
+    expect: {
+        var test = [ "a", "b", "c" ];
+        for (const o of test) {
+            let t;
+            console.log(o), t = [ "e", "f", "g" ];
+            for (const o of t)
+                console.log(o);
+        }
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}
+
+same_variable_in_multiple_forIn_sequences_let: {
+    options = {
+        hoist_funs: true,
+        dead_code: true,
+        conditionals: true,
+        comparisons: true,
+        evaluate: true,
+        booleans: true,
+        loops: true,
+        unused: false,
+        keep_fargs: true,
+        if_return: true,
+        join_vars: true,
+        sequences: true,
+        side_effects: true,
+        collapse_vars: true,
+    }
+    mangle = {}
+    input: {
+        var test = [ "a", "b", "c" ];
+        for (let tmp in test) {
+            console.log(tmp);
+            let dd;
+            dd = [ "e", "f", "g" ];
+            for (let tmp in test) {
+                console.log(tmp);
+            }
+        }
+    }
+    expect: {
+        var test = [ "a", "b", "c" ];
+        for (let e in test) {
+            let t;
+            console.log(e), t = [ "e", "f", "g" ];
+            for (let e in test)
+                console.log(e);
+        }
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}
+
+same_variable_in_multiple_forIn_sequences_const: {
+    options = {
+        hoist_funs: true,
+        dead_code: true,
+        conditionals: true,
+        comparisons: true,
+        evaluate: true,
+        booleans: true,
+        loops: true,
+        unused: false,
+        keep_fargs: true,
+        if_return: true,
+        join_vars: true,
+        sequences: true,
+        side_effects: true,
+        collapse_vars: true,
+    }
+    mangle = {}
+    input: {
+        var test = [ "a", "b", "c" ];
+        for (const tmp in test) {
+            console.log(tmp);
+            let dd;
+            dd = [ "e", "f", "g" ];
+            for (const tmp in test) {
+                console.log(tmp);
+            }
+        }
+    }
+    expect: {
+        var test = [ "a", "b", "c" ];
+        for (const o in test) {
+            let t;
+            console.log(o), t = [ "e", "f", "g" ];
+            for (const o in test)
+                console.log(o);
+        }
+    }
+    expect_stdout: true
+    node_version: ">=6"
 }
 
 more_variable_in_multiple_for: {
@@ -283,4 +455,5 @@ more_variable_in_multiple_for: {
         }
     }
     expect_stdout: true
+    node_version: ">=6"
 }