From 5b7d1906408c40f6c0292ea1072f5874a4300454 Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Tue, 17 Apr 2018 15:39:09 -0400
Subject: [PATCH] Emit RedundantCondition when asserting two variables can
 never be equal

---
 .../Checker/Statements/Block/TryChecker.php   |  6 +-
 .../Statements/Expression/AssertionFinder.php | 64 +++++++++++++++++++
 tests/TypeAlgebraTest.php                     |  7 ++
 3 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/src/Psalm/Checker/Statements/Block/TryChecker.php b/src/Psalm/Checker/Statements/Block/TryChecker.php
index f4f422a61..43700347a 100644
--- a/src/Psalm/Checker/Statements/Block/TryChecker.php
+++ b/src/Psalm/Checker/Statements/Block/TryChecker.php
@@ -275,9 +275,9 @@ class TryChecker
 
             if ($catch_actions[$i] !== [ScopeChecker::ACTION_END]) {
                 foreach ($catch_context->vars_in_scope as $var_id => $type) {
-                    if ($catch->var !== $var_id &&
-                        $context->hasVariable($var_id) &&
-                        $context->vars_in_scope[$var_id]->getId() !== $type->getId()
+                    if ((!is_string($catch->var->name) || ('$' . $catch->var->name) !== $var_id)
+                        && $context->hasVariable($var_id)
+                        && $context->vars_in_scope[$var_id]->getId() !== $type->getId()
                     ) {
                         $context->vars_in_scope[$var_id] = Type::combineUnionTypes(
                             $context->vars_in_scope[$var_id],
diff --git a/src/Psalm/Checker/Statements/Expression/AssertionFinder.php b/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
index ca39966f2..63f086ffc 100644
--- a/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
+++ b/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
@@ -7,6 +7,7 @@ use Psalm\Checker\Statements\ExpressionChecker;
 use Psalm\Checker\TypeChecker;
 use Psalm\CodeLocation;
 use Psalm\FileSource;
+use Psalm\Issue\RedundantCondition;
 use Psalm\Issue\TypeDoesNotContainNull;
 use Psalm\Issue\TypeDoesNotContainType;
 use Psalm\Issue\UnevaluatedCode;
@@ -442,6 +443,7 @@ class AssertionFinder
             $true_position = self::hasTrueVariable($conditional);
             $gettype_position = self::hasGetTypeCheck($conditional);
             $getclass_position = self::hasGetClassCheck($conditional);
+            $typed_value_position = self::hasTypedValueComparison($conditional);
 
             if ($null_position !== null) {
                 if ($null_position === self::ASSIGNMENT_TO_RIGHT) {
@@ -621,6 +623,68 @@ class AssertionFinder
                 return $if_types;
             }
 
+            if ($typed_value_position) {
+                if ($typed_value_position === self::ASSIGNMENT_TO_RIGHT) {
+                    /** @var PhpParser\Node\Expr $conditional->right */
+                    $var_name = ExpressionChecker::getArrayVarId(
+                        $conditional->left,
+                        $this_class_name,
+                        $source
+                    );
+
+                    $other_type = isset($conditional->left->inferredType) ? $conditional->left->inferredType : null;
+                    $var_type = isset($conditional->right->inferredType) ? $conditional->right->inferredType : null;
+                } elseif ($typed_value_position === self::ASSIGNMENT_TO_LEFT) {
+                    /** @var PhpParser\Node\Expr $conditional->left */
+                    $var_name = ExpressionChecker::getArrayVarId(
+                        $conditional->right,
+                        $this_class_name,
+                        $source
+                    );
+
+                    $var_type = isset($conditional->left->inferredType) ? $conditional->left->inferredType : null;
+                    $other_type = isset($conditional->right->inferredType) ? $conditional->right->inferredType : null;
+                } else {
+                    throw new \UnexpectedValueException('$typed_value_position value');
+                }
+
+                if ($var_type) {
+                    if ($var_name) {
+                        $if_types[$var_name] = '!^' . $var_type;
+                    }
+
+                    if ($other_type
+                        && $conditional instanceof PhpParser\Node\Expr\BinaryOp\NotIdentical
+                        && $source instanceof StatementsSource
+                        && $project_checker
+                    ) {
+                        if (!TypeChecker::isContainedBy(
+                            $project_checker->codebase,
+                            $var_type,
+                            $other_type,
+                            true
+                        ) && !TypeChecker::isContainedBy(
+                            $project_checker->codebase,
+                            $other_type,
+                            $var_type,
+                            true
+                        )) {
+                            if (IssueBuffer::accepts(
+                                new RedundantCondition(
+                                    $var_type . ' can never contain ' . $other_type,
+                                    new CodeLocation($source, $conditional)
+                                ),
+                                $source->getSuppressedIssues()
+                            )) {
+                                // fall through
+                            }
+                        }
+                    }
+                }
+
+                return $if_types;
+            }
+
             return [];
         }
 
diff --git a/tests/TypeAlgebraTest.php b/tests/TypeAlgebraTest.php
index a0995ba19..3d3732970 100644
--- a/tests/TypeAlgebraTest.php
+++ b/tests/TypeAlgebraTest.php
@@ -764,6 +764,13 @@ class TypeAlgebraTest extends TestCase
                     }',
                 'error_message' => 'ParadoxicalCondition',
             ],
+            'typeDoesntEqualType' => [
+                '<?php
+                    $a = "hello";
+                    $b = 5;
+                    if ($a !== $b) {}',
+                'error_message' => 'RedundantCondition',
+            ],
         ];
     }
 }