Empty checks variables are really falsy checks

vimeo · Oct 24, 2020 · 94e26b2 · 94e26b2
1 parent 5ff3f13
commit 94e26b2
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Showing 2 changed files with 23 additions and 1 deletion.
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php b/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
@@ -484,7 +484,16 @@ public static function scrapeAssertions(
             );
 
             if ($var_name) {
-                $if_types[$var_name] = [['empty']];
+                if ($conditional->expr instanceof PhpParser\Node\Expr\Variable
+                    && $source instanceof StatementsAnalyzer
+                    && ($var_type = $source->node_data->getType($conditional->expr))
+                    && !$var_type->isMixed()
+                    && !$var_type->possibly_undefined
+                ) {
+                    $if_types[$var_name] = [['falsy']];
+                } else {
+                    $if_types[$var_name] = [['empty']];
+                }
             }
 
             return $if_types;

diff --git a/tests/TypeReconciliation/TypeAlgebraTest.php b/tests/TypeReconciliation/TypeAlgebraTest.php
@@ -1271,6 +1271,19 @@ function foo(string $input) : string {
                     }',
                 'error_message' => 'ParadoxicalCondition',
             ],
+            'mismatchingChecks' => [
+                '<?php
+                    function doesntFindBug(?string $old, ?string $new): void {
+                        if (empty($old) && empty($new)) {
+                            return;
+                        }
+
+                        if (($old && empty($new)) || ($new && empty($old))) {
+                            return;
+                        }
+                    }',
+                'error_message' => 'RedundantCondition',
+            ],
         ];
     }
 }