2 files changed, 78 insertions, 0 deletions

diff --git a/lib/compress.js b/lib/compress.js
index a2666fa9..f49486a0 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2651,6 +2651,10 @@ merge(Compressor.prototype, {
 
         // y?true:false --> !!y
         if (is_true(consequent) && is_false(alternative)) {
+            if (self.condition.is_boolean()) {
+                // boolean_expression ? true : false --> boolean_expression
+                return self.condition;
+            }
             self.condition = self.condition.negate(compressor);
             return make_node(AST_UnaryPrefix, self.condition, {
                 operator: "!",
diff --git a/test/compress/conditionals.js b/test/compress/conditionals.js
index 65cfea64..db0d8000 100644
--- a/test/compress/conditionals.js
+++ b/test/compress/conditionals.js
@@ -738,3 +738,77 @@ conditional_or: {
         a = condition + 3    || null;
     }
 }
+
+trivial_boolean_ternary_expressions : {
+    options = {
+        conditionals: true,
+        evaluate    : true,
+        booleans    : true
+    };
+    input: {
+        f('foo' in m ? true  : false);
+        f('foo' in m ? false : true);
+
+        f(g       ? true : false);
+        f(foo()   ? true : false);
+        f("bar"   ? true : false);
+        f(5       ? true : false);
+        f(5.7     ? true : false);
+        f(x - y   ? true : false);
+
+        f(x == y  ? true : false);
+        f(x === y ?   !0 :    !1);
+        f(x < y   ?   !0 : false);
+        f(x <= y  ? true : false);
+        f(x > y   ? true :    !1);
+        f(x >= y  ?   !0 :    !1);
+
+        f(g       ? false : true);
+        f(foo()   ? false : true);
+        f("bar"   ? false : true);
+        f(5       ? false : true);
+        f(5.7     ? false : true);
+        f(x - y   ? false : true);
+
+        f(x == y  ?    !1 :   !0);
+        f(x === y ? false : true);
+
+        f(x < y   ? false : true);
+        f(x <= y  ? false :   !0);
+        f(x > y   ?    !1 : true);
+        f(x >= y  ?    !1 :   !0);
+    }
+    expect: {
+        f('foo' in m);
+        f(!('foo' in m));
+
+        f(!!g);
+        f(!!foo());
+        f(!0);
+        f(!0);
+        f(!0);
+        f(!!(x - y));
+
+        f(x == y);
+        f(x === y);
+        f(x < y);
+        f(x <= y);
+        f(x > y);
+        f(x >= y);
+
+        f(!g);
+        f(!foo());
+        f(!1);
+        f(!1);
+        f(!1);
+        f(!(x - y));
+
+        f(x != y);
+        f(x !== y);
+
+        f(!(x < y));
+        f(!(x <= y));
+        f(!(x > y));
+        f(!(x >= y));
+    }
+}