Fix incorrect parse of integer values for double vars (#1024)

Values like `{"a": 101}` were parsed incorrectly during JSON parsing.

They're internally interpreted as being integer and during assignment to double variable it were bit-casted from `int` to `double`, which is wrong.

This PR fixes this behavior. Now integer values are converted to double explicitly.

runtime/from-json-processor.h

@@ -79,7 +79,7 @@ class FromJsonVisitor {
       on_input_type_mismatch(json);
       return;
     }
-    value = json.as_double();
+    value = json.is_int() ? json.as_int() : json.as_double();
   }
 
   void do_set(string &value, const mixed &json) noexcept {

tests/phpt/json/37_json_float_read.php

@@ -0,0 +1,23 @@
+<?php
+require_once 'kphp_tester_include.php';
+
+class MoneyRequest {
+  private float $amount;
+
+  public function __construct(float $amount) {
+    $this->amount = $amount;
+  }
+
+  public function getAmount(): float {
+    return $this->amount;
+  }
+}
+
+function test_json_float_read(): void {
+  $raw = '{"amount":101}';
+
+  $res = JsonEncoder::decode($raw, MoneyRequest::class);
+  var_dump($res->getAmount());
+}
+
+test_json_float_read();