Fix #1859 - allow function_exists introspection when function exists

src/Psalm/Internal/Analyzer/StatementsAnalyzer.php

@@ -150,8 +150,12 @@ class StatementsAnalyzer extends SourceAnalyzer implements StatementsSource
         // hoist functions to the top
         foreach ($stmts as $stmt) {
             if ($stmt instanceof PhpParser\Node\Stmt\Function_) {
+                try {
                     $function_analyzer = new FunctionAnalyzer($stmt, $this->source);
                     $this->function_analyzers[strtolower($stmt->name->name)] = $function_analyzer;
+                } catch (\UnexpectedValueException $e) {
+                    // do nothing
+                }
             }
         }
 
@@ -542,6 +546,8 @@ class StatementsAnalyzer extends SourceAnalyzer implements StatementsSource
                     $config = Config::getInstance();
                     $function_context->collect_references = $codebase->collect_references;
                     $function_context->collect_exceptions = $config->check_for_throws_docblock;
+
+                    if (isset($this->function_analyzers[$function_id])) {
                         $this->function_analyzers[$function_id]->analyze($function_context, $context);
 
                         if ($config->reportIssueInFile('InvalidReturnType', $this->getFilePath())) {
@@ -563,6 +569,7 @@ class StatementsAnalyzer extends SourceAnalyzer implements StatementsSource
                             );
                         }
                     }
+                }
             } elseif ($stmt instanceof PhpParser\Node\Stmt\Expression) {
                 if (ExpressionAnalyzer::analyze($this, $stmt->expr, $context, false, $global_context) === false) {
                     return false;

tests/ClassStringTest.php

@@ -611,6 +611,15 @@ class ClassStringTest extends TestCase
                         new \RuntimeException();
                     }'
             ],
+
+            'noCrashWhenClassExistsNegated' => [
+                '<?php
+                    class A {}
+
+                    if (!class_exists(A::class)) {
+                        new \RuntimeException();
+                    }'
+            ],
         ];
     }
 

tests/FunctionCallTest.php

@@ -1760,6 +1760,14 @@ class FunctionCallTest extends TestCase
                         $f->bar();
                     }'
             ],
+            'functionExists' => [
+                '<?php
+                    if (!function_exists("in_array")) {
+                        function in_array($a, $b) {
+                            return true;
+                        }
+                    }'
+            ],
         ];
     }