From fd19dfaebc74cc0f4927e1acaca7c82c961728f8 Mon Sep 17 00:00:00 2001
From: epriestley <epriestley@phabricator.com>
Date: Thu, 10 Mar 2011 15:11:41 -0800
Subject: [PATCH] Detect use of "+" on a string literal in PHP.

Summary:
This is realistically always wrong and the author means "."

Test Plan:
lint / unit

Reviewed By: crackerjack
Reviewers: crackerjack, aran
CC: crackerjack
Differential Revision: 68
---
 .../linter/xhpast/ArcanistXHPASTLinter.php    | 24 +++++++++++++++++++
 .../data/wrong-concat-operator.lint-test      |  9 +++++++
 2 files changed, 33 insertions(+)
 create mode 100644 src/lint/linter/xhpast/__tests__/data/wrong-concat-operator.lint-test

diff --git a/src/lint/linter/xhpast/ArcanistXHPASTLinter.php b/src/lint/linter/xhpast/ArcanistXHPASTLinter.php
index fd2f1c8f..d6aafab7 100644
--- a/src/lint/linter/xhpast/ArcanistXHPASTLinter.php
+++ b/src/lint/linter/xhpast/ArcanistXHPASTLinter.php
@@ -45,6 +45,7 @@ class ArcanistXHPASTLinter extends ArcanistLinter {
   const LINT_COMMENT_STYLE            = 18;
   const LINT_CLASS_FILENAME_MISMATCH  = 19;
   const LINT_TAUTOLOGICAL_EXPRESSION  = 20;
+  const LINT_PLUS_OPERATOR_ON_STRINGS = 21;
 
 
   public function getLintNameMap() {
@@ -69,6 +70,7 @@ class ArcanistXHPASTLinter extends ArcanistLinter {
       self::LINT_COMMENT_STYLE            => 'Comment Style',
       self::LINT_CLASS_FILENAME_MISMATCH  => 'Class-Filename Mismatch',
       self::LINT_TAUTOLOGICAL_EXPRESSION  => 'Tautological Expression',
+      self::LINT_PLUS_OPERATOR_ON_STRINGS => 'Not String Concatenation',
     );
   }
 
@@ -146,6 +148,7 @@ class ArcanistXHPASTLinter extends ArcanistLinter {
     $this->lintHashComments($root);
     $this->lintPrimaryDeclarationFilenameMatch($root);
     $this->lintTautologicalExpressions($root);
+    $this->lintPlusOperatorOnStrings($root);
   }
 
   private function lintTautologicalExpressions($root) {
@@ -977,6 +980,27 @@ class ArcanistXHPASTLinter extends ArcanistLinter {
     );
   }
 
+  private function lintPlusOperatorOnStrings($root) {
+    $binops = $root->selectDescendantsOfType('n_BINARY_EXPRESSION');
+    foreach ($binops as $binop) {
+      $op = $binop->getChildByIndex(1);
+      if ($op->getConcreteString() != '+') {
+        continue;
+      }
+
+      $left = $binop->getChildByIndex(0);
+      $right = $binop->getChildByIndex(2);
+      if (($left->getTypeName() == 'n_STRING_SCALAR') ||
+          ($right->getTypeName() == 'n_STRING_SCALAR')) {
+        $this->raiseLintAtNode(
+          $binop,
+          self::LINT_PLUS_OPERATOR_ON_STRINGS,
+          "In PHP, '.' is the string concatenation operator, not '+'. This ".
+          "expression uses '+' with a string literal as an operand.");
+      }
+    }
+  }
+
   protected function raiseLintAtToken(
     XHPASTToken $token,
     $code,
diff --git a/src/lint/linter/xhpast/__tests__/data/wrong-concat-operator.lint-test b/src/lint/linter/xhpast/__tests__/data/wrong-concat-operator.lint-test
new file mode 100644
index 00000000..aaf0de4d
--- /dev/null
+++ b/src/lint/linter/xhpast/__tests__/data/wrong-concat-operator.lint-test
@@ -0,0 +1,9 @@
+<?php
+"a"."b";
+"a" + "b";
+"a" + $x;
+$x + $y + $z + "q" + 0;
+~~~~~~~~~~
+error:3:1
+error:4:1
+error:5:1