enhance inline (#5610)

lib/compress.js

@@ -10825,7 +10825,7 @@ Compressor.prototype.compress = function(node) {
             var begin;
             var in_order = [];
             var side_effects = false;
-            value.walk(new TreeWalker(function(node, descend) {
+            var tw = new TreeWalker(function(node, descend) {
                 if (abort) return true;
                 if (node instanceof AST_Binary && lazy_op[node.operator]
                     || node instanceof AST_Conditional) {
@@ -10841,7 +10841,7 @@ Compressor.prototype.compress = function(node) {
                         return;
                     }
                     if (def.init instanceof AST_LambdaDefinition) return abort = true;
-                    if (is_lhs(node, this.parent())) return abort = true;
+                    if (is_lhs(node, tw.parent())) return abort = true;
                     var index = resolve_index(def);
                     if (!(begin < index)) begin = index;
                     if (!in_order) return;
@@ -10852,12 +10852,21 @@ Compressor.prototype.compress = function(node) {
                     }
                     return;
                 }
+                if (side_effects) return;
+                if (node instanceof AST_Assign && node.left instanceof AST_PropAccess) {
+                    node.left.expression.walk(tw);
+                    if (node.left instanceof AST_Sub) node.left.property.walk(tw);
+                    node.right.walk(tw);
+                    side_effects = true;
+                    return true;
+                }
                 if (node.has_side_effects(compressor)) {
                     descend();
                     side_effects = true;
                     return true;
                 }
-            }));
+            });
+            value.walk(tw);
             if (abort) return;
             var end = self.args.length;
             if (in_order && fn.argnames.length >= end) {

test/compress/functions.js

@@ -5512,6 +5512,40 @@ substitute_use_strict: {
     ]
 }
 
+substitute_assignment: {
+    options = {
+        evaluate: true,
+        inline: true,
+        passes: 2,
+        properties: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a, b, c) {
+            a[b] = c;
+        }
+        var o = {};
+        f(o, 42, null);
+        f(o, "foo", "bar");
+        for (var k in o)
+            console.log(k, o[k]);
+    }
+    expect: {
+        var o = {};
+        o[42] = null;
+        o.foo = "bar";
+        for (var k in o)
+            console.log(k, o[k]);
+    }
+    expect_stdout: [
+        "42 null",
+        "foo bar",
+    ]
+}
+
 issue_3833_1: {
     options = {
         inline: 3,