<?php
namespace Psalm\Internal\Analyzer;

use Psalm\Codebase;
use Psalm\CodeLocation;
use Psalm\Internal\Analyzer\Statements\ExpressionAnalyzer;
use Psalm\Internal\MethodIdentifier;
use Psalm\Issue\ImplementedParamTypeMismatch;
use Psalm\Issue\ImplementedReturnTypeMismatch;
use Psalm\Issue\MethodSignatureMismatch;
use Psalm\Issue\MoreSpecificImplementedParamType;
use Psalm\Issue\LessSpecificImplementedReturnType;
use Psalm\Issue\OverriddenMethodAccess;
use Psalm\Issue\TraitMethodSignatureMismatch;
use Psalm\IssueBuffer;
use Psalm\Storage\ClassLikeStorage;
use Psalm\Storage\FunctionLikeParameter;
use Psalm\Storage\MethodStorage;
use Psalm\Type;
use function strtolower;
use function is_string;
use function in_array;
use Psalm\Issue\MissingImmutableAnnotation;

class MethodComparator
{
    /**
     * @param  ClassLikeStorage $implementer_classlike_storage
     * @param  ClassLikeStorage $guide_classlike_storage
     * @param  MethodStorage    $implementer_method_storage
     * @param  MethodStorage    $guide_method_storage
     * @param  CodeLocation     $code_location
     * @param  string[]         $suppressed_issues
     * @param  bool             $prevent_abstract_override
     * @param  bool             $prevent_method_signature_mismatch
     *
     * @return false|null
     */
    public static function compare(
        Codebase $codebase,
        ClassLikeStorage $implementer_classlike_storage,
        ClassLikeStorage $guide_classlike_storage,
        MethodStorage $implementer_method_storage,
        MethodStorage $guide_method_storage,
        string $implementer_called_class_name,
        int $implementer_visibility,
        CodeLocation $code_location,
        array $suppressed_issues,
        $prevent_abstract_override = true,
        $prevent_method_signature_mismatch = true
    ) {
        $implementer_declaring_method_id = $codebase->methods->getDeclaringMethodId(
            new MethodIdentifier(
                $implementer_classlike_storage->name,
                strtolower($guide_method_storage->cased_name ?: '')
            )
        );

        $cased_implementer_method_id = $implementer_classlike_storage->name . '::'
            . $implementer_method_storage->cased_name;

        $cased_guide_method_id = $guide_classlike_storage->name . '::' . $guide_method_storage->cased_name;

        self::checkForObviousMethodMismatches(
            $guide_classlike_storage,
            $implementer_classlike_storage,
            $guide_method_storage,
            $implementer_method_storage,
            $guide_method_storage->visibility,
            $implementer_visibility,
            $cased_guide_method_id,
            $cased_implementer_method_id,
            $prevent_method_signature_mismatch,
            $prevent_abstract_override,
            $code_location,
            $suppressed_issues
        );

        if ($guide_method_storage->signature_return_type && $prevent_method_signature_mismatch) {
            self::compareMethodSignatureReturnTypes(
                $codebase,
                $guide_classlike_storage,
                $implementer_classlike_storage,
                $guide_method_storage,
                $implementer_method_storage,
                $guide_method_storage->signature_return_type,
                $cased_guide_method_id,
                $cased_implementer_method_id,
                $code_location,
                $suppressed_issues
            );
        }

        if ($guide_method_storage->return_type
            && $implementer_method_storage->return_type
            && !$implementer_method_storage->inherited_return_type
            && ($guide_method_storage->signature_return_type !== $guide_method_storage->return_type
                || $implementer_method_storage->signature_return_type !== $implementer_method_storage->return_type)
            && $implementer_classlike_storage->user_defined
            && (!$guide_classlike_storage->stubbed || $guide_classlike_storage->template_types)
        ) {
            self::compareMethodDocblockReturnTypes(
                $codebase,
                $guide_classlike_storage,
                $implementer_classlike_storage,
                $implementer_method_storage,
                $guide_method_storage->return_type,
                $implementer_method_storage->return_type,
                $cased_guide_method_id,
                $implementer_called_class_name,
                $implementer_declaring_method_id,
                $code_location,
                $suppressed_issues
            );
        }

        foreach ($guide_method_storage->params as $i => $guide_param) {
            if (!isset($implementer_method_storage->params[$i])) {
                if (!$prevent_abstract_override && $i >= $guide_method_storage->required_param_count) {
                    continue;
                }

                if (IssueBuffer::accepts(
                    new MethodSignatureMismatch(
                        'Method ' . $cased_implementer_method_id . ' has fewer parameters than parent method ' .
                            $cased_guide_method_id,
                        $code_location
                    )
                )) {
                    return false;
                }

                return null;
            }

            self::compareMethodParams(
                $codebase,
                $implementer_classlike_storage,
                $guide_classlike_storage,
                $implementer_called_class_name,
                $guide_method_storage,
                $implementer_method_storage,
                $guide_param,
                $implementer_method_storage->params[$i],
                $i,
                $cased_guide_method_id,
                $cased_implementer_method_id,
                $prevent_method_signature_mismatch,
                $code_location,
                $suppressed_issues
            );
        }

        if ($guide_classlike_storage->user_defined
            && ($guide_classlike_storage->is_interface || $implementer_method_storage->cased_name !== '__construct')
            && $implementer_method_storage->required_param_count > $guide_method_storage->required_param_count
        ) {
            if (IssueBuffer::accepts(
                new MethodSignatureMismatch(
                    'Method ' . $cased_implementer_method_id . ' has more required parameters than parent method ' .
                        $cased_guide_method_id,
                    $code_location
                )
            )) {
                return false;
            }

            return null;
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function checkForObviousMethodMismatches(
        ClassLikeStorage $guide_classlike_storage,
        ClassLikeStorage $implementer_classlike_storage,
        MethodStorage $guide_method_storage,
        MethodStorage $implementer_method_storage,
        int $guide_visibility,
        int $implementer_visibility,
        string $cased_guide_method_id,
        string $cased_implementer_method_id,
        bool $prevent_method_signature_mismatch,
        bool $prevent_abstract_override,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        if ($implementer_visibility > $guide_visibility) {
            if ($guide_classlike_storage->is_trait === $implementer_classlike_storage->is_trait
                || !in_array($guide_classlike_storage->name, $implementer_classlike_storage->used_traits)
                || $implementer_method_storage->defining_fqcln !== $implementer_classlike_storage->name
                || (!$implementer_method_storage->abstract
                    && !$guide_method_storage->abstract)
            ) {
                if (IssueBuffer::accepts(
                    new OverriddenMethodAccess(
                        'Method ' . $cased_implementer_method_id . ' has different access level than '
                            . $cased_guide_method_id,
                        $code_location
                    )
                )) {
                    // fall through
                }
            } elseif (IssueBuffer::accepts(
                new TraitMethodSignatureMismatch(
                    'Method ' . $cased_implementer_method_id . ' has different access level than '
                        . $cased_guide_method_id,
                    $code_location
                )
            )) {
                // fall through
            }
        }

        if ($guide_method_storage->final
            && $prevent_method_signature_mismatch
            && $prevent_abstract_override
        ) {
            if (IssueBuffer::accepts(
                new MethodSignatureMismatch(
                    'Method ' . $cased_guide_method_id . ' is declared final and cannot be overridden',
                    $code_location
                )
            )) {
                // fall through
            }
        }

        if ($prevent_abstract_override
            && !$guide_method_storage->abstract
            && $implementer_method_storage->abstract
            && !$guide_classlike_storage->abstract
            && !$guide_classlike_storage->is_interface
        ) {
            if (IssueBuffer::accepts(
                new MethodSignatureMismatch(
                    'Method ' . $cased_implementer_method_id . ' cannot be abstract when inherited method '
                        . $cased_guide_method_id . ' is non-abstract',
                    $code_location
                )
            )) {
                // fall through
            }
        }

        if ($guide_method_storage->external_mutation_free
            && !$implementer_method_storage->external_mutation_free
            && !$guide_method_storage->mutation_free_inferred
            && $prevent_method_signature_mismatch
        ) {
            if (IssueBuffer::accepts(
                new MissingImmutableAnnotation(
                    $cased_guide_method_id . ' is marked immutable, but '
                        . $implementer_classlike_storage->name . '::'
                        . ($guide_method_storage->cased_name ?: '')
                        . ' is not marked immutable',
                    $code_location
                ),
                $suppressed_issues
            )) {
                // fall through
            }
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function compareMethodParams(
        Codebase $codebase,
        ClassLikeStorage $implementer_classlike_storage,
        ClassLikeStorage $guide_classlike_storage,
        string $implementer_called_class_name,
        MethodStorage $guide_method_storage,
        MethodStorage $implementer_method_storage,
        FunctionLikeParameter $guide_param,
        FunctionLikeParameter $implementer_param,
        int $i,
        string $cased_guide_method_id,
        string $cased_implementer_method_id,
        bool $prevent_method_signature_mismatch,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        if ($prevent_method_signature_mismatch) {
            if (!$guide_classlike_storage->user_defined
                && $guide_param->type
            ) {
                $implementer_param_type = $implementer_param->signature_type;

                $guide_param_signature_type = $guide_param->type;

                $or_null_guide_param_signature_type = $guide_param->signature_type
                    ? clone $guide_param->signature_type
                    : null;

                if ($or_null_guide_param_signature_type) {
                    $or_null_guide_param_signature_type->addType(new Type\Atomic\TNull);
                }

                if ($cased_guide_method_id === 'Serializable::unserialize') {
                    $guide_param_signature_type = null;
                    $or_null_guide_param_signature_type = null;
                }

                if (!$guide_param->type->hasMixed()
                    && !$guide_param->type->from_docblock
                    && ($implementer_param_type || $guide_param_signature_type)
                ) {
                    $config = \Psalm\Config::getInstance();

                    if ($implementer_param_type
                        && (!$guide_param_signature_type
                            || strtolower($implementer_param_type->getId())
                                !== strtolower($guide_param_signature_type->getId()))
                        && (!$or_null_guide_param_signature_type
                            || strtolower($implementer_param_type->getId())
                                !== strtolower($or_null_guide_param_signature_type->getId()))
                    ) {
                        if (IssueBuffer::accepts(
                            new MethodSignatureMismatch(
                                'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id . ' has wrong type \'' .
                                    $implementer_param_type . '\', expecting \'' .
                                    $guide_param_signature_type . '\' as defined by ' .
                                    $cased_guide_method_id,
                                $implementer_param->location
                                    && $config->isInProjectDirs(
                                        $implementer_param->location->file_path
                                    )
                                    ? $implementer_param->location
                                    : $code_location
                            )
                        )) {
                            // fall through
                        }

                        return;
                    }
                }
            }

            if ($guide_classlike_storage->user_defined
                && $implementer_param->signature_type
            ) {
                self::compareMethodSignatureParams(
                    $codebase,
                    $i,
                    $guide_classlike_storage,
                    $implementer_classlike_storage,
                    $guide_method_storage,
                    $implementer_method_storage,
                    $guide_param,
                    $implementer_param->signature_type,
                    $cased_guide_method_id,
                    $cased_implementer_method_id,
                    $code_location,
                    $suppressed_issues
                );
            }
        }

        if ($implementer_param->type
            && $guide_param->type
            && $implementer_param->type->getId() !== $guide_param->type->getId()
        ) {
            self::compareMethodDocblockParams(
                $codebase,
                $i,
                $guide_classlike_storage,
                $implementer_classlike_storage,
                $implementer_called_class_name,
                $guide_method_storage,
                $implementer_method_storage,
                $cased_guide_method_id,
                $cased_implementer_method_id,
                $guide_param->type,
                $implementer_param->type,
                $code_location,
                $suppressed_issues
            );
        }

        if ($guide_classlike_storage->user_defined && $implementer_param->by_ref !== $guide_param->by_ref) {
            $config = \Psalm\Config::getInstance();

            if (IssueBuffer::accepts(
                new MethodSignatureMismatch(
                    'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id . ' is' .
                        ($implementer_param->by_ref ? '' : ' not') . ' passed by reference, but argument ' .
                        ($i + 1) . ' of ' . $cased_guide_method_id . ' is' . ($guide_param->by_ref ? '' : ' not'),
                    $implementer_param->location
                        && $config->isInProjectDirs(
                            $implementer_param->location->file_path
                        )
                        ? $implementer_param->location
                        : $code_location
                )
            )) {
                // fall through
            }
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function compareMethodSignatureParams(
        Codebase $codebase,
        int $i,
        ClassLikeStorage $guide_classlike_storage,
        ClassLikeStorage $implementer_classlike_storage,
        MethodStorage $guide_method_storage,
        MethodStorage $implementer_method_storage,
        FunctionLikeParameter $guide_param,
        Type\Union $implementer_param_signature_type,
        string $cased_guide_method_id,
        string $cased_implementer_method_id,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        $guide_param_signature_type = $guide_param->signature_type
            ? ExpressionAnalyzer::fleshOutType(
                $codebase,
                $guide_param->signature_type,
                $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                    ? $implementer_classlike_storage->name
                    : $guide_classlike_storage->name,
                $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                    ? $implementer_classlike_storage->name
                    : $guide_classlike_storage->name,
                $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                    ? $implementer_classlike_storage->parent_class
                    : $guide_classlike_storage->parent_class
            )
            : null;

        $implementer_param_signature_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $implementer_param_signature_type,
            $implementer_classlike_storage->name,
            $implementer_classlike_storage->name,
            $implementer_classlike_storage->parent_class
        );

        $is_contained_by = $codebase->php_major_version >= 7
            && $codebase->php_minor_version >= 4
            && $guide_param_signature_type
            ? TypeAnalyzer::isContainedBy(
                $codebase,
                $guide_param_signature_type,
                $implementer_param_signature_type
            )
            : TypeAnalyzer::isContainedByInPhp(
                $guide_param_signature_type,
                $implementer_param_signature_type
            );
        if (!$is_contained_by) {
            $config = \Psalm\Config::getInstance();

            if ($guide_classlike_storage->is_trait === $implementer_classlike_storage->is_trait
                || !in_array($guide_classlike_storage->name, $implementer_classlike_storage->used_traits)
                || $implementer_method_storage->defining_fqcln !== $implementer_classlike_storage->name
                || (!$implementer_method_storage->abstract
                    && !$guide_method_storage->abstract)
            ) {
                if (IssueBuffer::accepts(
                    new MethodSignatureMismatch(
                        'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id . ' has wrong type \'' .
                            $implementer_param_signature_type . '\', expecting \'' .
                            $guide_param_signature_type . '\' as defined by ' .
                            $cased_guide_method_id,
                        $implementer_method_storage->params[$i]->location
                            && $config->isInProjectDirs(
                                $implementer_method_storage->params[$i]->location->file_path
                            )
                            ? $implementer_method_storage->params[$i]->location
                            : $code_location
                    )
                )) {
                    // fall through
                }
            } else {
                if (IssueBuffer::accepts(
                    new TraitMethodSignatureMismatch(
                        'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id . ' has wrong type \'' .
                            $implementer_param_signature_type . '\', expecting \'' .
                            $guide_param_signature_type . '\' as defined by ' .
                            $cased_guide_method_id,
                        $implementer_method_storage->params[$i]->location
                            && $config->isInProjectDirs(
                                $implementer_method_storage->params[$i]->location->file_path
                            )
                            ? $implementer_method_storage->params[$i]->location
                            : $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            }
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function compareMethodDocblockParams(
        Codebase $codebase,
        int $i,
        ClassLikeStorage $guide_classlike_storage,
        ClassLikeStorage $implementer_classlike_storage,
        string $implementer_called_class_name,
        MethodStorage $guide_method_storage,
        MethodStorage $implementer_method_storage,
        string $cased_guide_method_id,
        string $cased_implementer_method_id,
        Type\Union $guide_param_type,
        Type\Union $implementer_param_type,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        $implementer_method_storage_param_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $implementer_param_type,
            $implementer_classlike_storage->name,
            $implementer_called_class_name,
            $implementer_classlike_storage->parent_class
        );

        $guide_method_storage_param_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $guide_param_type,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->parent_class
                : $guide_classlike_storage->parent_class
        );

        $guide_class_name = $guide_classlike_storage->name;

        if ($implementer_classlike_storage->template_type_extends) {
            self::transformTemplates(
                $implementer_classlike_storage->template_type_extends,
                $guide_class_name,
                $guide_method_storage_param_type,
                $codebase
            );
        }

        if ($implementer_classlike_storage->is_trait) {
            $implementer_called_class_storage = $codebase->classlike_storage_provider->get(
                $implementer_called_class_name
            );

            if (isset(
                $implementer_called_class_storage->template_type_extends[$implementer_classlike_storage->name]
            )) {
                self::transformTemplates(
                    $implementer_called_class_storage->template_type_extends,
                    $implementer_classlike_storage->name,
                    $implementer_method_storage_param_type,
                    $codebase
                );

                self::transformTemplates(
                    $implementer_called_class_storage->template_type_extends,
                    $guide_class_name,
                    $guide_method_storage_param_type,
                    $codebase
                );
            }
        }

        $union_comparison_results = new TypeComparisonResult();

        if (!TypeAnalyzer::isContainedBy(
            $codebase,
            $guide_method_storage_param_type,
            $implementer_method_storage_param_type,
            !$guide_classlike_storage->user_defined,
            !$guide_classlike_storage->user_defined,
            $union_comparison_results
        )) {
            // is the declared return type more specific than the inferred one?
            if ($union_comparison_results->type_coerced) {
                if ($guide_classlike_storage->user_defined) {
                    if (IssueBuffer::accepts(
                        new MoreSpecificImplementedParamType(
                            'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id
                                . ' has the more specific type \'' .
                                $implementer_method_storage_param_type->getId() . '\', expecting \'' .
                                $guide_method_storage_param_type->getId() . '\' as defined by ' .
                                $cased_guide_method_id,
                            $implementer_method_storage->params[$i]->location
                                ?: $code_location
                        ),
                        $suppressed_issues
                    )) {
                        // fall through
                    }
                }
            } else {
                if (TypeAnalyzer::isContainedBy(
                    $codebase,
                    $implementer_method_storage_param_type,
                    $guide_method_storage_param_type,
                    !$guide_classlike_storage->user_defined,
                    !$guide_classlike_storage->user_defined
                )) {
                    if (IssueBuffer::accepts(
                        new MoreSpecificImplementedParamType(
                            'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id
                                . ' has the more specific type \'' .
                                $implementer_method_storage_param_type->getId() . '\', expecting \'' .
                                $guide_method_storage_param_type->getId() . '\' as defined by ' .
                                $cased_guide_method_id,
                            $implementer_method_storage->params[$i]->location
                                ?: $code_location
                        ),
                        $suppressed_issues
                    )) {
                         // fall through
                    }
                } else {
                    if (IssueBuffer::accepts(
                        new ImplementedParamTypeMismatch(
                            'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id
                                . ' has wrong type \'' .
                                $implementer_method_storage_param_type->getId() . '\', expecting \'' .
                                $guide_method_storage_param_type->getId() . '\' as defined by ' .
                                $cased_guide_method_id,
                            $implementer_method_storage->params[$i]->location
                                ?: $code_location
                        ),
                        $suppressed_issues
                    )) {
                         // fall through
                    }
                }
            }
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function compareMethodSignatureReturnTypes(
        Codebase $codebase,
        ClassLikeStorage $guide_classlike_storage,
        ClassLikeStorage $implementer_classlike_storage,
        MethodStorage $guide_method_storage,
        MethodStorage $implementer_method_storage,
        Type\Union $guide_signature_return_type,
        string $cased_guide_method_id,
        string $cased_implementer_method_id,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        $guide_signature_return_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $guide_signature_return_type,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->is_trait && $guide_method_storage->abstract
                ? $implementer_classlike_storage->parent_class
                : $guide_classlike_storage->parent_class
        );

        $implementer_signature_return_type = $implementer_method_storage->signature_return_type
            ? ExpressionAnalyzer::fleshOutType(
                $codebase,
                $implementer_method_storage->signature_return_type,
                $implementer_classlike_storage->name,
                $implementer_classlike_storage->name,
                $implementer_classlike_storage->parent_class
            ) : null;

        $is_contained_by = $codebase->php_major_version >= 7
            && $codebase->php_minor_version >= 4
            && $implementer_signature_return_type
            ? TypeAnalyzer::isContainedBy(
                $codebase,
                $implementer_signature_return_type,
                $guide_signature_return_type
            )
            : TypeAnalyzer::isContainedByInPhp($implementer_signature_return_type, $guide_signature_return_type);

        if (!$is_contained_by) {
            if ($guide_classlike_storage->is_trait === $implementer_classlike_storage->is_trait
                || !in_array($guide_classlike_storage->name, $implementer_classlike_storage->used_traits)
                || $implementer_method_storage->defining_fqcln !== $implementer_classlike_storage->name
                || (!$implementer_method_storage->abstract
                    && !$guide_method_storage->abstract)
            ) {
                if (IssueBuffer::accepts(
                    new MethodSignatureMismatch(
                        'Method ' . $cased_implementer_method_id . ' with return type \''
                            . $implementer_signature_return_type . '\' is different to return type \''
                            . $guide_signature_return_type . '\' of inherited method ' . $cased_guide_method_id,
                        $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            } else {
                if (IssueBuffer::accepts(
                    new TraitMethodSignatureMismatch(
                        'Method ' . $cased_implementer_method_id . ' with return type \''
                            . $implementer_signature_return_type . '\' is different to return type \''
                            . $guide_signature_return_type . '\' of inherited method ' . $cased_guide_method_id,
                        $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            }
        }
    }

    /**
     * @param  string[]         $suppressed_issues
     */
    private static function compareMethodDocblockReturnTypes(
        Codebase $codebase,
        ClassLikeStorage $guide_classlike_storage,
        ClassLikeStorage $implementer_classlike_storage,
        MethodStorage $implementer_method_storage,
        Type\Union $guide_return_type,
        Type\Union $implementer_return_type,
        string $cased_guide_method_id,
        string $implementer_called_class_name,
        ?MethodIdentifier $implementer_declaring_method_id,
        CodeLocation $code_location,
        array $suppressed_issues
    ) : void {
        $implementer_method_storage_return_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $implementer_return_type,
            $implementer_classlike_storage->name,
            $implementer_called_class_name,
            $implementer_classlike_storage->parent_class
        );

        $guide_method_storage_return_type = ExpressionAnalyzer::fleshOutType(
            $codebase,
            $guide_return_type,
            $guide_classlike_storage->is_trait
                ? $implementer_classlike_storage->name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->is_trait
                ? $implementer_called_class_name
                : $guide_classlike_storage->name,
            $guide_classlike_storage->parent_class
        );

        $guide_class_name = $guide_classlike_storage->name;

        if ($implementer_classlike_storage->template_type_extends) {
            self::transformTemplates(
                $implementer_classlike_storage->template_type_extends,
                $guide_class_name,
                $guide_method_storage_return_type,
                $codebase
            );
        }

        if ($implementer_classlike_storage->is_trait) {
            $implementer_called_class_storage = $codebase->classlike_storage_provider->get(
                $implementer_called_class_name
            );

            if (isset(
                $implementer_called_class_storage->template_type_extends[$implementer_classlike_storage->name]
            )) {
                self::transformTemplates(
                    $implementer_called_class_storage->template_type_extends,
                    $implementer_classlike_storage->name,
                    $implementer_method_storage_return_type,
                    $codebase
                );

                self::transformTemplates(
                    $implementer_called_class_storage->template_type_extends,
                    $guide_class_name,
                    $guide_method_storage_return_type,
                    $codebase
                );
            }
        }

        // treat void as null when comparing against docblock implementer
        if ($implementer_method_storage_return_type->isVoid()) {
            $implementer_method_storage_return_type = Type::getNull();
        }

        if ($guide_method_storage_return_type->isVoid()) {
            $guide_method_storage_return_type = Type::getNull();
        }

        $union_comparison_results = new TypeComparisonResult();

        if (!TypeAnalyzer::isContainedBy(
            $codebase,
            $implementer_method_storage_return_type,
            $guide_method_storage_return_type,
            false,
            false,
            $union_comparison_results
        )) {
            // is the declared return type more specific than the inferred one?
            if ($union_comparison_results->type_coerced) {
                if (IssueBuffer::accepts(
                    new LessSpecificImplementedReturnType(
                        'The inherited return type \'' . $guide_method_storage_return_type->getId()
                            . '\' for ' . $cased_guide_method_id . ' is more specific than the implemented '
                            . 'return type for ' . $implementer_declaring_method_id . ' \''
                            . $implementer_method_storage_return_type->getId() . '\'',
                        $implementer_method_storage->return_type_location
                            ?: $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            } else {
                if (IssueBuffer::accepts(
                    new ImplementedReturnTypeMismatch(
                        'The inherited return type \'' . $guide_method_storage_return_type->getId()
                            . '\' for ' . $cased_guide_method_id . ' is different to the implemented '
                            . 'return type for ' . $implementer_declaring_method_id . ' \''
                            . $implementer_method_storage_return_type->getId() . '\'',
                        $implementer_method_storage->return_type_location
                            ?: $code_location
                    ),
                    $suppressed_issues
                )) {
                    // fall through
                }
            }
        }
    }

    /**
     * @param  array<string, array<int|string, Type\Union>>  $template_type_extends
     */
    private static function transformTemplates(
        array $template_type_extends,
        string $base_class_name,
        Type\Union $templated_type,
        Codebase $codebase
    ) : void {
        if (isset($template_type_extends[$base_class_name])) {
            $map = $template_type_extends[$base_class_name];

            $template_types = [];

            foreach ($map as $key => $mapped_type) {
                if (is_string($key)) {
                    $new_bases = [];

                    foreach ($mapped_type->getAtomicTypes() as $mapped_atomic_type) {
                        if ($mapped_atomic_type instanceof Type\Atomic\TTemplateParam) {
                            $new_bases[] = $mapped_atomic_type->defining_class;
                        }
                    }

                    if ($new_bases) {
                        $mapped_type = clone $mapped_type;

                        foreach ($new_bases as $new_base_class_name) {
                            self::transformTemplates(
                                $template_type_extends,
                                $new_base_class_name,
                                $mapped_type,
                                $codebase
                            );
                        }
                    }

                    $template_types[$key][$base_class_name] = [$mapped_type];
                }
            }

            $template_result = new \Psalm\Internal\Type\TemplateResult($template_types, []);

            $templated_type->replaceTemplateTypesWithArgTypes(
                $template_result->template_types,
                $codebase
            );
        }
    }
}