dart2dart: Logical operators and related rewrite rules in dart_tree.

sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart
index 95ef81c85dfa08e5d1fbf1897844bc252f735e6a..c636063c4279499d5ef896105b9931dac522848e 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/tree_tracer.dart
@@ -52,6 +52,8 @@ class BlockCollector extends Visitor {
   visitConcatenateStrings(ConcatenateStrings node) {}
   visitConstant(Constant node) {}
   visitConditional(Conditional node) {}
+  visitLogicalOperator(LogicalOperator node) {}
+  visitNot(Not node) {}
 
   visitLabeledStatement(LabeledStatement node) {
     Block target = new Block();
@@ -186,6 +188,14 @@ class TreeTracer extends TracerUtil with Visitor {
     printStatement(null, expr(node));
   }
 
+  visitLogicalOperator(LogicalOperator node) {
+    printStatement(null, expr(node));
+  }
+
+  visitNot(Not node) {
+    printStatement(null, expr(node));
+  }
+
   visitReturn(Return node) {
     printStatement(null, "return ${expr(node.value)}");
   }
@@ -266,10 +276,35 @@ class SubexpressionVisitor extends Visitor<String, String> {
     return "${node.value}";
   }
 
+  bool usesInfixNotation(Expression node) {
+    return node is Conditional || node is LogicalOperator;

[Kevin Millikin (Google), 2014/05/19 11:36:41]

The implementation doesn't seem to match the name.  I  worry that it either
doesn't scale or is a source of later bugs.

I would expect an implementation like !usesPrefixNotation(node) &&
!usesPostfixNotation(node).  Alternately, a different approach in terms of
precedence.

I guess it's fine for now.

[asgerf, 2014/05/19 13:29:07]

Yeah we need proper precedence-awareness. Right now, things like (x ? y :
z).foo() will be printed as x ? y : z.foo() in the tracer.

+  }
+
   String visitConditional(Conditional node) {
-    return visitExpression(node.condition) + ' ? ' +
-           visitExpression(node.thenExpression) + ' : ' +
-           visitExpression(node.elseExpression);
+    String condition = visitExpression(node.condition);
+    String thenExpr = visitExpression(node.thenExpression);
+    String elseExpr = visitExpression(node.elseExpression);
+    return "$condition ? $thenExpr : $elseExpr";
+  }
+
+  String visitLogicalOperator(LogicalOperator node) {
+    String left = visitExpression(node.left);
+    String right = visitExpression(node.right);
+    if (usesInfixNotation(node.left)) {
+      left = "($left)";
+    }
+    if (usesInfixNotation(node.right)) {
+      right = "($right)";
+    }
+    return "$left ${node.operator} $right";
+  }
+
+  String visitNot(Not node) {
+    String operand = visitExpression(node.operand);
+    if (usesInfixNotation(node.operand)) {
+      operand = '($operand)';
+    }
+    return '!$operand';
   }
 
   // Note: There should not be statements in the context of expressions.