Allow weak equality between scalar types

src/Psalm/Type/Reconciler.php

@@ -663,6 +663,8 @@ class Reconciler
                 );
             }
 
+            $any_scalar_type_match_found = false;
+
             foreach ($new_type->getTypes() as $new_type_part) {
                 $has_local_match = false;
 
@@ -689,6 +691,10 @@ class Reconciler
                         break;
                     }
 
+                    if ($scalar_type_match_found) {
+                        $any_scalar_type_match_found = true;
+                    }
+
                     if ($new_type_part instanceof TCallable &&
                         (
                             $existing_var_type_part instanceof TString ||
@@ -712,7 +718,7 @@ class Reconciler
                 }
             }
 
-            if (!$has_match) {
+            if (!$has_match && (!$is_loose_equality || !$any_scalar_type_match_found)) {
                 if ($new_var_type === 'null') {
                     if ($existing_var_type->from_docblock) {
                         if (IssueBuffer::accepts(

tests/TypeReconciliationTest.php

@@ -819,6 +819,12 @@ class TypeReconciliationTest extends TestCase
                         }
                     }',
             ],
+            'allowWeakEqualityScalarType' => [
+                '<?php
+                    function foo(int $i) : void {
+                        if ($i == "5") {}
+                    }',
+            ],
         ];
     }
 
@@ -948,6 +954,13 @@ class TypeReconciliationTest extends TestCase
                     if (is_bool($a[0]) && $a[0]) {}',
                 'error_message' => 'DocblockTypeContradiction',
             ],
+            'preventWeakEqualityToObject' => [
+                '<?php
+                    function foo(int $i, stdClass $s) : void {
+                        if ($i == $s) {}
+                    }',
+                'error_message' => 'TypeDoesNotContainType',
+            ],
         ];
     }
 }