From 80494384081ea4b2f82b05d957cd223209fef5c1 Mon Sep 17 00:00:00 2001
From: orklah <ronan_morin@hotmail.com>
Date: Sat, 1 Jan 2022 11:13:45 +0100
Subject: [PATCH 1/2] forbid calling impure callable in immutable context

---
 src/Psalm/Context.php                         |  2 ++
 .../Expression/Call/FunctionCallAnalyzer.php  |  2 +-
 tests/PureAnnotationTest.php                  | 32 +++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/Psalm/Context.php b/src/Psalm/Context.php
index fd90976fd8a..3b9470d6f64 100644
--- a/src/Psalm/Context.php
+++ b/src/Psalm/Context.php
@@ -353,11 +353,13 @@ class Context
 
     /**
      * @var bool
+     * Set by @psalm-immutable
      */
     public $mutation_free = false;
 
     /**
      * @var bool
+     * Set by @psalm-external-mutation-free
      */
     public $external_mutation_free = false;
 
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php
index 1fa7cdf11b9..bdc1dcbb8aa 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php
@@ -642,7 +642,7 @@ private static function getAnalyzeNamedExpression(
                 }
 
                 if ($var_type_part instanceof TClosure || $var_type_part instanceof TCallable) {
-                    if (!$var_type_part->is_pure && $context->pure) {
+                    if (!$var_type_part->is_pure && ($context->pure || $context->mutation_free)) {
                         IssueBuffer::maybeAdd(
                             new ImpureFunctionCall(
                                 'Cannot call an impure function from a mutation-free context',
diff --git a/tests/PureAnnotationTest.php b/tests/PureAnnotationTest.php
index b9264f20ebe..988459f9167 100644
--- a/tests/PureAnnotationTest.php
+++ b/tests/PureAnnotationTest.php
@@ -876,6 +876,38 @@ function testImpure(): void
                     ',
                 'error_message' => 'ImpureMethodCall',
             ],
+            'impureCallableInImmutableContext' => [
+                '<?php
+
+                    /**
+                     * @psalm-immutable
+                     */
+                    class Either
+                    {
+                        /**
+                         * @psalm-param callable $_
+                         */
+                        public function fold($_): void
+                        {
+                            $_();
+                        }
+                    }
+
+                    class Whatever
+                    {
+                        public function __construct()
+                        {
+                            $either = new Either();
+                            $either->fold(
+                                function (): void {}
+                            );
+                        }
+                    }
+
+                    new Whatever();
+                    ',
+                'error_message' => 'ImpureFunctionCall',
+            ],
         ];
     }
 }

From 8e5c9f02bbef37afb41dffcbaa833c6ae7103caa Mon Sep 17 00:00:00 2001
From: orklah <ronan_morin@hotmail.com>
Date: Sat, 1 Jan 2022 11:21:43 +0100
Subject: [PATCH 2/2] fix test

---
 tests/Template/ClassTemplateTest.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Template/ClassTemplateTest.php b/tests/Template/ClassTemplateTest.php
index ff2f03cfec1..eca908c2bdf 100644
--- a/tests/Template/ClassTemplateTest.php
+++ b/tests/Template/ClassTemplateTest.php
@@ -2991,7 +2991,7 @@ public function toString(): string
 
                         /**
                          * @psalm-template TResult
-                         * @psalm-param callable(self::READ_UNCOMMITTED): TResult $readUncommitted
+                         * @psalm-param pure-callable(self::READ_UNCOMMITTED): TResult $readUncommitted
                          * @psalm-return TResult
                          */
                         public function resolve(callable $readUncommitted) {