fix unknown property access

lib/compress.js

@@ -611,8 +611,9 @@ merge(Compressor.prototype, {
             } else if (parent instanceof AST_Array || parent instanceof AST_Object) {
                 mark_escaped(d, parent, parent, level + 1);
             } else if (parent instanceof AST_PropAccess && node === parent.expression) {
-                mark_escaped(d, parent, read_property(value, parent.property), level + 1);
-                return;
+                value = read_property(value, parent.property);
+                mark_escaped(d, parent, value, level + 1);
+                if (value) return;
             }
             if (level == 0) d.direct_access = true;
         }

test/compress/hoist_props.js

@@ -98,7 +98,7 @@ issue_2377_3: {
     expect_stdout: "1 27"
 }
 
-direct_access: {
+direct_access_1: {
     options = {
         reduce_vars: true,
         hoist_props: true,
@@ -129,6 +129,55 @@ direct_access: {
     expect_stdout: "2 1"
 }
 
+direct_access_2: {
+    options = {
+        reduce_vars: true,
+        hoist_props: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        var o = { a: 1 };
+        var f = function(k) {
+            if (o[k]) return "PASS";
+        };
+        console.log(f("a"));
+    }
+    expect: {
+        var n = { a: 1 };
+        console.log(function(o) {
+            if (n[o]) return "PASS";
+        }("a"));
+    }
+    expect_stdout: "PASS"
+}
+
+direct_access_3: {
+    options = {
+        reduce_vars: true,
+        hoist_props: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        var o = { a: 1 };
+        o.b;
+        console.log(o.a);
+    }
+    expect: {
+        var a = { a: 1 };
+        a.b;
+        console.log(a.a);
+    }
+    expect_stdout: "1"
+}
+
 single_use: {
     options = {
         reduce_vars: true,