Fix int and float compatibility in union types

This was broken in commit
0479532
as withType may be called in union type context.
First calling withValue() to set an int value and then updating the type
with withType() does not trigger the float cast, in turn causing a
mapping error.

Developed by: Social Deal (@socialdeal)

src/Mapper/Tree/Shell.php

@@ -80,6 +80,7 @@ public function withType(Type $newType): self
     {
         $clone = clone $this;
         $clone->type = $newType;
+        $clone->value = self::castCompatibleValue($newType, $this->value);
 
         return $clone;
     }
@@ -91,17 +92,9 @@ public function type(): Type
 
     public function withValue(mixed $value): self
     {
-        // When the value is an integer and the type is a float, the value is
-        // cast to float, to follow the rule of PHP regarding acceptance of an
-        // integer value in a float type. Note that PHPStan/Psalm analysis
-        // applies the same rule.
-        if ($this->type instanceof FloatType && is_int($value)) {
-            $value = (float)$value;
-        }
-
         $clone = clone $this;
         $clone->hasValue = true;
-        $clone->value = $value;
+        $clone->value = self::castCompatibleValue($clone->type, $value);
 
         return $clone;
     }
@@ -173,4 +166,17 @@ public function path(): string
 
         return implode('.', $path);
     }
+
+    private static function castCompatibleValue(Type $type, mixed $value): mixed
+    {
+        // When the value is an integer and the type is a float, the value is
+        // cast to float, to follow the rule of PHP regarding acceptance of an
+        // integer value in a float type. Note that PHPStan/Psalm analysis
+        // applies the same rule.
+        if ($type instanceof FloatType && is_int($value)) {
+            return (float)$value;
+        }
+
+        return $value;
+    }
 }

tests/Integration/Mapping/UnionMappingTest.php

@@ -64,6 +64,15 @@ public static function union_mapping_works_properly_data_provider(): iterable
             'assertion' => fn (mixed $result) => self::assertNull($result),
         ];
 
+        yield 'nullable float with integer value' => [
+            'type' => 'float|null',
+            'source' => 42,
+            'assertion' => function (mixed $result) {
+                self::assertIsFloat($result);
+                self::assertEquals(42.0, $result);
+            },
+        ];
+
         yield 'string or list of string, with string' => [
             'type' => 'string|list<string>',
             'source' => 'foo',