Improve "and"/"or" compatibility with reference implementation

Author: robocoder

src/Compiler.php

@@ -1151,8 +1151,7 @@ protected function filterWithout($envs, $without)
                 $ec->block = null;
                 $ec->selectors = [];
                 $filtered[] = $ec;
-            }
-            else {
+            } else {
                 $filtered[] = $e;
             }
         }
@@ -2937,8 +2936,14 @@ protected function opAdd($left, $right)
      */
     protected function opAnd($left, $right, $shouldEval)
     {
+        $truthy = ($left === static::$null || $right === static::$null) ||
+                  ($left === static::$false || $left === static::$true) &&
+                  ($right === static::$false || $right === static::$true);
+
         if (! $shouldEval) {
-            return null;
+            if (! $truthy) {
+                return null;
+            }
         }
 
         if ($left !== static::$false && $left !== static::$null) {
@@ -2959,8 +2964,14 @@ protected function opAnd($left, $right, $shouldEval)
      */
     protected function opOr($left, $right, $shouldEval)
     {
+        $truthy = ($left === static::$null || $right === static::$null) ||
+                  ($left === static::$false || $left === static::$true) &&
+                  ($right === static::$false || $right === static::$true);
+
         if (! $shouldEval) {
-            return null;
+            if (! $truthy) {
+                return null;
+            }
         }
 
         if ($left !== static::$false && $left !== static::$null) {

tests/inputs/operators.scss

@@ -191,3 +191,37 @@ $gridRowWidth: 20px;
 {
 width: (2.5 / $gridRowWidth * 100px * 1% );
 }
+
+$and: true and false;
+$or: false or true;
+
+$and1: null and true;  // (null)
+$and2: true and null;  // (null)
+$and3: null and false; // (null)
+$and4: false and null; // false
+$and5: one and null;   // (null)
+$and6: null and one;   // (null)
+
+$or1: null or true;    // true
+$or2: true or null;    // true
+$or3: null or false;   // false
+$or4: false or null;   // (null)
+$or5: one or null;     // one
+$or6: null or one;     // one
+
+#bools-test {
+  a: $and;
+  b: $or;
+  c: $and1;
+  d: $and2;
+  e: $and3;
+  f: $and4;
+  g: $and5;
+  h: $and6;
+  n: $or1;
+  o: $or2;
+  p: $or3;
+  q: $or4;
+  r: $or5;
+  s: $or6;
+}

tests/outputs/operators.css

@@ -173,3 +173,13 @@ div {
 
 .foo {
   width: 12.5%; }
+
+#bools-test {
+  a: false;
+  b: true;
+  f: false;
+  n: true;
+  o: true;
+  p: false;
+  r: one;
+  s: one; }

tests/outputs_numbered/operators.css

@@ -174,3 +174,13 @@ div {
 /* line 190, inputs/operators.scss */
 .foo {
   width: 12.5%; }
+/* line 212, inputs/operators.scss */
+#bools-test {
+  a: false;
+  b: true;
+  f: false;
+  n: true;
+  o: true;
+  p: false;
+  r: one;
+  s: one; }