fix a couple of bugs in global_defs

- `optimize()` substituted expression
- compute nested property string correctly

fixes #1801

lib/compress.js

@@ -1346,7 +1346,7 @@ merge(Compressor.prototype, {
         }
         def(AST_Node, noop);
         def(AST_Dot, function(compressor, suffix){
-            return this.expression._find_defs(compressor, suffix + "." + this.property);
+            return this.expression._find_defs(compressor, "." + this.property + suffix);
         });
         def(AST_SymbolRef, function(compressor, suffix){
             if (!this.global()) return;
@@ -3566,7 +3566,7 @@ merge(Compressor.prototype, {
     OPT(AST_SymbolRef, function(self, compressor){
         var def = self.resolve_defines(compressor);
         if (def) {
-            return def;
+            return def.optimize(compressor);
         }
         // testing against !self.scope.uses_with first is an optimization
         if (compressor.option("screw_ie8")
@@ -3916,7 +3916,7 @@ merge(Compressor.prototype, {
     OPT(AST_Dot, function(self, compressor){
         var def = self.resolve_defines(compressor);
         if (def) {
-            return def;
+            return def.optimize(compressor);
         }
         var prop = self.property;
         if (RESERVED_WORDS(prop) && !compressor.option("screw_ie8")) {

test/compress/global_defs.js

@@ -145,3 +145,18 @@ mixed: {
         'WARN: global_defs CONFIG.VALUE redefined [test/compress/global_defs.js:129,8]',
     ]
 }
+
+issue_1801: {
+    options = {
+        booleans: true,
+        global_defs: {
+            "CONFIG.FOO.BAR": true,
+        },
+    }
+    input: {
+        console.log(CONFIG.FOO.BAR);
+    }
+    expect: {
+        console.log(!0);
+    }
+}