Handle more boolean conversion cases.

lib/src/compiler/code_generator.dart

Index: lib/src/compiler/code_generator.dart
diff --git a/lib/src/compiler/code_generator.dart b/lib/src/compiler/code_generator.dart
index be0dc06fd553c9d925704116ea161195f880a5ff..4c8001751fb93d265197105016866d1a2c5c5d3b 100644
--- a/lib/src/compiler/code_generator.dart
+++ b/lib/src/compiler/code_generator.dart
@@ -3468,6 +3468,14 @@ class CodeGenerator extends GeneralizingAstVisitor
   @override
   JS.Expression visitBinaryExpression(BinaryExpression node) {
     var op = node.operator;
+
+    // The operands of logical boolean operators are subject to boolean
+    // conversion.
+    if (op.type == TokenType.BAR_BAR ||
+        op.type == TokenType.AMPERSAND_AMPERSAND) {
+      return _visitTest(node);

[Jennifer Messerly, 2016/06/07 19:28:35]

Reading this, I was confused ... my thought was "shouldn't the check be on the
operands, not the result?"

I see that _visitTest is implemented to "push down" the check, so it works. Not
sure if it's worth a comment.

It does seem pretty cool that _visitTest is the place with the knowledge of all
boolean operations. I wonder if _emitBooleanOperation or something like that
might describe its role (just brainstorming ... not sure the right name).

+    }
+
     var left = node.leftOperand;
     var right = node.rightOperand;
 
@@ -3923,6 +3931,11 @@ class CodeGenerator extends GeneralizingAstVisitor
   @override
   JS.Expression visitPrefixExpression(PrefixExpression node) {
     var op = node.operator;
+
+    // Logical negation, `!e`, is a boolean conversion context since it is
+    // defined as `e ? false : true`.
+    if (op.lexeme == '!') return _visitTest(node);
+
     var expr = node.operand;
 
     var dispatchType = getStaticType(expr);