fix assignment extraction from conditional (#1651)

fixes #1645
fixes #1646

lib/compress.js

@@ -3550,19 +3550,17 @@ merge(Compressor.prototype, {
         }
         var consequent = self.consequent;
         var alternative = self.alternative;
+        // if (foo) exp = something; else exp = something_else;
+        //                   |
+        //                   v
+        // exp = foo ? something : something_else;
         if (consequent instanceof AST_Assign
             && alternative instanceof AST_Assign
             && consequent.operator == alternative.operator
             && consequent.left.equivalent_to(alternative.left)
-            && (!consequent.left.has_side_effects(compressor)
+            && (!self.condition.has_side_effects(compressor)
-                || !self.condition.has_side_effects(compressor))
+                || consequent.operator == "="
-           ) {
+                    && !consequent.left.has_side_effects(compressor))) {
-            /*
-             * Stuff like this:
-             * if (foo) exp = something; else exp = something_else;
-             * ==>
-             * exp = foo ? something : something_else;
-             */
             return make_node(AST_Assign, self, {
                 operator: consequent.operator,
                 left: consequent.left,

test/compress/conditionals.js

@@ -893,3 +893,43 @@ equality_conditionals_true: {
     }
     expect_stdout: true
 }
+
+issue_1645_1: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        var a = 100, b = 10;
+        (b = a) ? a++ + (b += a) ? b += a : b += a : b ^= a;
+        console.log(a, b);
+    }
+    expect: {
+        var a = 100, b = 10;
+        (b = a) ? (a++ + (b += a), b += a) : b ^= a;
+        console.log(a,b);
+    }
+    expect_stdout: true
+}
+
+issue_1645_2: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        var a = 0;
+        function f() {
+            return a++;
+        }
+        f() ? a += 2 : a += 4;
+        console.log(a);
+    }
+    expect: {
+        var a = 0;
+        function f(){
+            return a++;
+        }
+        f() ? a += 2 : a += 4;
+        console.log(a);
+    }
+    expect_stdout: true
+}