fix corner case in evaluate (#3938)

fixes #3937

lib/compress.js

@@ -3493,7 +3493,7 @@ merge(Compressor.prototype, {
             var fixed = this.fixed_value();
             if (!fixed) return this;
             var value;
-            if (member(fixed, cached)) {
+            if (HOP(fixed, "_eval")) {
                 value = fixed._eval();
             } else {
                 this._eval = return_this;

test/compress/evaluate.js

@@ -2669,3 +2669,24 @@ issue_3935: {
     }
     expect_stdout: "NaN"
 }
+
+issue_3937: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        var a = 123;
+        (a++ + (b = a))[b] ? 0 ? a : b : 0 ? a : b;
+        console.log(a, b);
+    }
+    expect: {
+        var a = 123;
+        (a++ + (b = a))[b], 0, b;
+        console.log(a, b);
+    }
+    expect_stdout: "124 124"
+}