Add column type inference to placeholders

Author: muglug

src/Processor/Expression/Evaluator.php

@@ -236,6 +236,15 @@ public static function getColumnSchema(
                     return self::getColumnTypeFromValue($expr, $scope->parameters[$expr->parameterName]);
                 }
 
+                // When MySQL can't figure out a variable column's type
+                // it defaults to string
+                return new Column\Varchar(10);
+
+            case \Vimeo\MysqlEngine\Query\Expression\PlaceholderExpression::class:
+                if (\array_key_exists($expr->offset, $scope->parameters)) {
+                    return self::getColumnTypeFromValue($expr, $scope->parameters[$expr->offset]);
+                }
+
                 // When MySQL can't figure out a variable column's type
                 // it defaults to string
                 return new Column\Varchar(10);