<?php
namespace Psalm\Internal\Analyzer\Statements\Expression;

use PhpParser;
use Psalm\Internal\Analyzer\CommentAnalyzer;
use Psalm\Internal\Analyzer\Statements\Block\ForeachAnalyzer;
use Psalm\Internal\Analyzer\Statements\Expression\Assignment\ArrayAssignmentAnalyzer;
use Psalm\Internal\Analyzer\Statements\Expression\Assignment\PropertyAssignmentAnalyzer;
use Psalm\Internal\Analyzer\Statements\ExpressionAnalyzer;
use Psalm\Internal\Analyzer\StatementsAnalyzer;
use Psalm\Internal\Analyzer\TypeAnalyzer;
use Psalm\CodeLocation;
use Psalm\Context;
use Psalm\Exception\DocblockParseException;
use Psalm\Exception\IncorrectDocblockException;
use Psalm\Internal\FileManipulation\FileManipulationBuffer;
use Psalm\Issue\AssignmentToVoid;
use Psalm\Issue\ImpureByReferenceAssignment;
use Psalm\Issue\ImpurePropertyAssignment;
use Psalm\Issue\InvalidArrayOffset;
use Psalm\Issue\InvalidDocblock;
use Psalm\Issue\InvalidScope;
use Psalm\Issue\LoopInvalidation;
use Psalm\Issue\MissingDocblockType;
use Psalm\Issue\MixedAssignment;
use Psalm\Issue\NoValue;
use Psalm\Issue\PossiblyUndefinedArrayOffset;
use Psalm\Issue\ReferenceConstraintViolation;
use Psalm\Issue\UnnecessaryVarAnnotation;
use Psalm\IssueBuffer;
use Psalm\Type;
use function is_string;
use function strpos;
use function strtolower;

/**
 * @internal
 */
class AssignmentAnalyzer
{
    /**
     * @param  StatementsAnalyzer        $statements_analyzer
     * @param  PhpParser\Node\Expr      $assign_var
     * @param  PhpParser\Node\Expr|null $assign_value  This has to be null to support list destructuring
     * @param  Type\Union|null          $assign_value_type
     * @param  Context                  $context
     * @param  ?PhpParser\Comment\Doc   $doc_comment
     *
     * @return false|Type\Union
     */
    public static function analyze(
        StatementsAnalyzer $statements_analyzer,
        PhpParser\Node\Expr $assign_var,
        $assign_value,
        $assign_value_type,
        Context $context,
        ?PhpParser\Comment\Doc $doc_comment
    ) {
        $var_id = ExpressionAnalyzer::getVarId(
            $assign_var,
            $statements_analyzer->getFQCLN(),
            $statements_analyzer
        );

        // gets a variable id that *may* contain array keys
        $array_var_id = ExpressionAnalyzer::getArrayVarId(
            $assign_var,
            $statements_analyzer->getFQCLN(),
            $statements_analyzer
        );

        $var_comments = [];
        $comment_type = null;
        $comment_type_location = null;

        $was_in_assignment = $context->inside_assignment;

        $context->inside_assignment = true;

        $codebase = $statements_analyzer->getCodebase();

        $remove_taint = false;

        if ($doc_comment) {
            $file_path = $statements_analyzer->getRootFilePath();

            $file_storage_provider = $codebase->file_storage_provider;

            $file_storage = $file_storage_provider->get($file_path);

            $template_type_map = $statements_analyzer->getTemplateTypeMap();

            try {
                $var_comments = CommentAnalyzer::getTypeFromComment(
                    $doc_comment,
                    $statements_analyzer->getSource(),
                    $statements_analyzer->getAliases(),
                    $template_type_map,
                    $file_storage->type_aliases
                );
            } catch (IncorrectDocblockException $e) {
                if (IssueBuffer::accepts(
                    new MissingDocblockType(
                        (string)$e->getMessage(),
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    )
                )) {
                    // fall through
                }
            } catch (DocblockParseException $e) {
                if (IssueBuffer::accepts(
                    new InvalidDocblock(
                        (string)$e->getMessage(),
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    )
                )) {
                    // fall through
                }
            }

            foreach ($var_comments as $var_comment) {
                if ($var_comment->remove_taint) {
                    $remove_taint = true;
                }

                if (!$var_comment->type) {
                    continue;
                }

                try {
                    $var_comment_type = ExpressionAnalyzer::fleshOutType(
                        $codebase,
                        $var_comment->type,
                        $context->self,
                        $context->self,
                        $statements_analyzer->getParentFQCLN()
                    );

                    $var_comment_type->setFromDocblock();

                    $var_comment_type->check(
                        $statements_analyzer,
                        new CodeLocation($statements_analyzer->getSource(), $assign_var),
                        $statements_analyzer->getSuppressedIssues(),
                        [],
                        false
                    );

                    $type_location = null;

                    if ($var_comment->type_start
                        && $var_comment->type_end
                        && $var_comment->line_number
                    ) {
                        $type_location = new CodeLocation\DocblockTypeLocation(
                            $statements_analyzer,
                            $var_comment->type_start,
                            $var_comment->type_end,
                            $var_comment->line_number
                        );

                        if ($codebase->alter_code) {
                            $codebase->classlikes->handleDocblockTypeInMigration(
                                $codebase,
                                $statements_analyzer,
                                $var_comment_type,
                                $type_location,
                                $context->calling_function_id
                            );
                        }
                    }

                    if (!$var_comment->var_id || $var_comment->var_id === $var_id) {
                        $comment_type = $var_comment_type;
                        $comment_type_location = $type_location;
                        continue;
                    }

                    if ($codebase->find_unused_variables
                        && $type_location
                        && isset($context->vars_in_scope[$var_comment->var_id])
                        && $context->vars_in_scope[$var_comment->var_id]->getId() === $var_comment_type->getId()
                        && !$var_comment_type->isMixed()
                    ) {
                        $project_analyzer = $statements_analyzer->getProjectAnalyzer();

                        if ($codebase->alter_code
                            && isset($project_analyzer->getIssuesToFix()['UnnecessaryVarAnnotation'])
                        ) {
                            FileManipulationBuffer::addVarAnnotationToRemove($type_location);
                        } elseif (IssueBuffer::accepts(
                            new UnnecessaryVarAnnotation(
                                'The @var ' . $var_comment_type . ' annotation for '
                                    . $var_comment->var_id . ' is unnecessary',
                                $type_location
                            ),
                            [],
                            true
                        )) {
                            // fall through
                        }
                    }

                    $context->vars_in_scope[$var_comment->var_id] = $var_comment_type;
                } catch (\UnexpectedValueException $e) {
                    if (IssueBuffer::accepts(
                        new InvalidDocblock(
                            (string)$e->getMessage(),
                            new CodeLocation($statements_analyzer->getSource(), $assign_var)
                        )
                    )) {
                        // fall through
                    }
                }
            }
        }

        if ($array_var_id) {
            unset($context->referenced_var_ids[$array_var_id]);
            $context->assigned_var_ids[$array_var_id] = true;
            $context->possibly_assigned_var_ids[$array_var_id] = true;
        }

        if ($assign_value) {
            if ($var_id && $assign_value instanceof PhpParser\Node\Expr\Closure) {
                foreach ($assign_value->uses as $closure_use) {
                    if ($closure_use->byRef
                        && is_string($closure_use->var->name)
                        && $var_id === '$' . $closure_use->var->name
                    ) {
                        $context->vars_in_scope[$var_id] = Type::getClosure();
                        $context->vars_possibly_in_scope[$var_id] = true;
                    }
                }
            }

            if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_value, $context) === false) {
                if ($var_id) {
                    if ($array_var_id) {
                        $context->removeDescendents($array_var_id, null, $assign_value_type);
                    }

                    // if we're not exiting immediately, make everything mixed
                    $context->vars_in_scope[$var_id] = $comment_type ?: Type::getMixed();
                }

                return false;
            }
        }

        if ($comment_type && $comment_type_location) {
            $temp_assign_value_type = $assign_value_type
                ? $assign_value_type
                : ($assign_value ? $statements_analyzer->node_data->getType($assign_value) : null);

            if ($codebase->find_unused_variables
                && $temp_assign_value_type
                && $array_var_id
                && $temp_assign_value_type->getId() === $comment_type->getId()
                && !$comment_type->isMixed()
            ) {
                if ($codebase->alter_code
                    && isset($statements_analyzer->getProjectAnalyzer()->getIssuesToFix()['UnnecessaryVarAnnotation'])
                ) {
                    FileManipulationBuffer::addVarAnnotationToRemove($comment_type_location);
                } elseif (IssueBuffer::accepts(
                    new UnnecessaryVarAnnotation(
                        'The @var ' . $comment_type . ' annotation for '
                            . $array_var_id . ' is unnecessary',
                        $comment_type_location
                    )
                )) {
                    // fall through
                }
            }

            $assign_value_type = $comment_type;
        } elseif (!$assign_value_type) {
            $assign_value_type = $assign_value
                ? ($statements_analyzer->node_data->getType($assign_value) ?: Type::getMixed())
                : Type::getMixed();
        }

        if ($array_var_id && isset($context->vars_in_scope[$array_var_id])) {
            if ($context->vars_in_scope[$array_var_id]->by_ref) {
                if ($context->mutation_free) {
                    if (IssueBuffer::accepts(
                        new ImpureByReferenceAssignment(
                            'Variable ' . $array_var_id . ' cannot be assigned to as it is passed by reference',
                            new CodeLocation($statements_analyzer->getSource(), $assign_var)
                        )
                    )) {
                        // fall through
                    }
                }

                $assign_value_type->by_ref = true;
            }

            // removes dependent vars from $context
            $context->removeDescendents(
                $array_var_id,
                $context->vars_in_scope[$array_var_id],
                $assign_value_type,
                $statements_analyzer
            );
        } else {
            $root_var_id = ExpressionAnalyzer::getRootVarId(
                $assign_var,
                $statements_analyzer->getFQCLN(),
                $statements_analyzer
            );

            if ($root_var_id && isset($context->vars_in_scope[$root_var_id])) {
                $context->removeVarFromConflictingClauses(
                    $root_var_id,
                    $context->vars_in_scope[$root_var_id],
                    $statements_analyzer
                );
            }
        }

        $codebase = $statements_analyzer->getCodebase();

        if ($assign_value_type->hasMixed()) {
            $root_var_id = ExpressionAnalyzer::getRootVarId(
                $assign_var,
                $statements_analyzer->getFQCLN(),
                $statements_analyzer
            );

            if (!$context->collect_initializations
                && !$context->collect_mutations
                && $statements_analyzer->getFilePath() === $statements_analyzer->getRootFilePath()
                && (!(($parent_source = $statements_analyzer->getSource())
                            instanceof \Psalm\Internal\Analyzer\FunctionLikeAnalyzer)
                        || !$parent_source->getSource() instanceof \Psalm\Internal\Analyzer\TraitAnalyzer)
            ) {
                $codebase->analyzer->incrementMixedCount($statements_analyzer->getFilePath());
            }

            if (!$assign_var instanceof PhpParser\Node\Expr\PropertyFetch
                && !strpos($root_var_id ?? '', '->')
                && !$comment_type
            ) {
                if (IssueBuffer::accepts(
                    new MixedAssignment(
                        'Cannot assign' . ($var_id ? ' ' . $var_id . ' ' : ' ') . 'to a mixed type',
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    ),
                    $statements_analyzer->getSuppressedIssues()
                )) {
                    // fall through
                }
            }
        } else {
            if (!$context->collect_initializations
                && !$context->collect_mutations
                && $statements_analyzer->getFilePath() === $statements_analyzer->getRootFilePath()
                && (!(($parent_source = $statements_analyzer->getSource())
                        instanceof \Psalm\Internal\Analyzer\FunctionLikeAnalyzer)
                    || !$parent_source->getSource() instanceof \Psalm\Internal\Analyzer\TraitAnalyzer)
            ) {
                $codebase->analyzer->incrementNonMixedCount($statements_analyzer->getFilePath());
            }

            if ($var_id
                && isset($context->byref_constraints[$var_id])
                && ($outer_constraint_type = $context->byref_constraints[$var_id]->type)
            ) {
                if (!TypeAnalyzer::isContainedBy(
                    $codebase,
                    $assign_value_type,
                    $outer_constraint_type,
                    $assign_value_type->ignore_nullable_issues,
                    $assign_value_type->ignore_falsable_issues
                )
                ) {
                    if (IssueBuffer::accepts(
                        new ReferenceConstraintViolation(
                            'Variable ' . $var_id . ' is limited to values of type '
                                . $context->byref_constraints[$var_id]->type
                                . ' because it is passed by reference, '
                                . $assign_value_type->getId() . ' type found',
                            new CodeLocation($statements_analyzer->getSource(), $assign_var)
                        ),
                        $statements_analyzer->getSuppressedIssues()
                    )) {
                        // fall through
                    }
                }
            }
        }

        if ($var_id === '$this' && IssueBuffer::accepts(
            new InvalidScope(
                'Cannot re-assign ' . $var_id,
                new CodeLocation($statements_analyzer->getSource(), $assign_var)
            ),
            $statements_analyzer->getSuppressedIssues()
        )) {
            return false;
        }

        if (isset($context->protected_var_ids[$var_id])) {
            if (IssueBuffer::accepts(
                new LoopInvalidation(
                    'Variable ' . $var_id . ' has already been assigned in a for/foreach loop',
                    new CodeLocation($statements_analyzer->getSource(), $assign_var)
                ),
                $statements_analyzer->getSuppressedIssues()
            )) {
                // fall through
            }
        }

        if ($assign_var instanceof PhpParser\Node\Expr\Variable) {
            if (is_string($assign_var->name)) {
                if ($var_id) {
                    $context->vars_in_scope[$var_id] = $assign_value_type;
                    $context->vars_possibly_in_scope[$var_id] = true;

                    $location = new CodeLocation($statements_analyzer, $assign_var);

                    if ($context->collect_references) {
                        $context->unreferenced_vars[$var_id] = [$location->getHash() => $location];
                    }

                    if (!$statements_analyzer->hasVariable($var_id)) {
                        $statements_analyzer->registerVariable(
                            $var_id,
                            $location,
                            $context->branch_point
                        );
                    } else {
                        $statements_analyzer->registerVariableAssignment(
                            $var_id,
                            $location
                        );
                    }

                    if (isset($context->byref_constraints[$var_id]) || $assign_value_type->by_ref) {
                        $statements_analyzer->registerVariableUses([$location->getHash() => $location]);
                    }
                }
            } else {
                if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_var->name, $context) === false) {
                    return false;
                }
            }
        } elseif ($assign_var instanceof PhpParser\Node\Expr\List_
            || $assign_var instanceof PhpParser\Node\Expr\Array_
        ) {
            if (!$assign_value_type->hasArray()
                && !$assign_value_type->isMixed()
                && !$assign_value_type->hasArrayAccessInterface($codebase)
            ) {
                if (IssueBuffer::accepts(
                    new InvalidArrayOffset(
                        'Cannot destructure non-array of type ' . $assign_value_type->getId(),
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    ),
                    $statements_analyzer->getSuppressedIssues()
                )) {
                    // fall through
                }
            }

            $can_be_empty = true;

            foreach ($assign_var->items as $offset => $assign_var_item) {
                // $assign_var_item can be null e.g. list($a, ) = ['a', 'b']
                if (!$assign_var_item) {
                    continue;
                }

                $var = $assign_var_item->value;

                if ($assign_value instanceof PhpParser\Node\Expr\Array_
                    && $statements_analyzer->node_data->getType($assign_var_item->value)
                ) {
                    self::analyze(
                        $statements_analyzer,
                        $var,
                        $assign_var_item->value,
                        null,
                        $context,
                        $doc_comment
                    );

                    continue;
                }

                $list_var_id = ExpressionAnalyzer::getArrayVarId(
                    $var,
                    $statements_analyzer->getFQCLN(),
                    $statements_analyzer
                );

                $new_assign_type = null;

                foreach ($assign_value_type->getAtomicTypes() as $assign_value_atomic_type) {
                    if ($assign_value_atomic_type instanceof Type\Atomic\ObjectLike
                        && !$assign_var_item->key
                        && isset($assign_value_atomic_type->properties[$offset]) // if object-like has int offsets
                    ) {
                        $offset_type = $assign_value_atomic_type->properties[(string)$offset];

                        if ($offset_type->possibly_undefined) {
                            if (IssueBuffer::accepts(
                                new PossiblyUndefinedArrayOffset(
                                    'Possibly undefined array key',
                                    new CodeLocation($statements_analyzer->getSource(), $var)
                                ),
                                $statements_analyzer->getSuppressedIssues()
                            )) {
                                // fall through
                            }

                            $offset_type = clone $offset_type;
                            $offset_type->possibly_undefined = false;
                        }

                        self::analyze(
                            $statements_analyzer,
                            $var,
                            null,
                            $offset_type,
                            $context,
                            $doc_comment
                        );

                        continue 2;
                    }

                    if ($var instanceof PhpParser\Node\Expr\List_
                        || $var instanceof PhpParser\Node\Expr\Array_
                    ) {
                        if ($assign_value_atomic_type instanceof Type\Atomic\ObjectLike) {
                            $assign_value_atomic_type = $assign_value_atomic_type->getGenericArrayType();
                        }

                        if ($assign_value_atomic_type instanceof Type\Atomic\TList) {
                            $assign_value_atomic_type = new Type\Atomic\TArray([
                                Type::getInt(),
                                $assign_value_atomic_type->type_param
                            ]);
                        }

                        self::analyze(
                            $statements_analyzer,
                            $var,
                            null,
                            $assign_value_atomic_type instanceof Type\Atomic\TArray
                                ? clone $assign_value_atomic_type->type_params[1]
                                : Type::getMixed(),
                            $context,
                            $doc_comment
                        );
                    }

                    if ($list_var_id) {
                        $context->vars_possibly_in_scope[$list_var_id] = true;
                        $context->assigned_var_ids[$list_var_id] = true;
                        $context->possibly_assigned_var_ids[$list_var_id] = true;

                        $already_in_scope = isset($context->vars_in_scope[$list_var_id]);

                        if (strpos($list_var_id, '-') === false && strpos($list_var_id, '[') === false) {
                            $location = new CodeLocation($statements_analyzer, $var);

                            if ($context->collect_references) {
                                $context->unreferenced_vars[$list_var_id] = [$location->getHash() => $location];
                            }

                            if (!$statements_analyzer->hasVariable($list_var_id)) {
                                $statements_analyzer->registerVariable(
                                    $list_var_id,
                                    $location,
                                    $context->branch_point
                                );
                            } else {
                                $statements_analyzer->registerVariableAssignment(
                                    $list_var_id,
                                    $location
                                );
                            }

                            if (isset($context->byref_constraints[$list_var_id])) {
                                $statements_analyzer->registerVariableUses([$location->getHash() => $location]);
                            }
                        }

                        if ($assign_value_atomic_type instanceof Type\Atomic\TArray) {
                            $new_assign_type = clone $assign_value_atomic_type->type_params[1];

                            $can_be_empty = !$assign_value_atomic_type instanceof Type\Atomic\TNonEmptyArray;
                        } elseif ($assign_value_atomic_type instanceof Type\Atomic\TList) {
                            $new_assign_type = clone $assign_value_atomic_type->type_param;

                            $can_be_empty = !$assign_value_atomic_type instanceof Type\Atomic\TNonEmptyList;
                        } elseif ($assign_value_atomic_type instanceof Type\Atomic\ObjectLike) {
                            if ($assign_var_item->key
                                && ($assign_var_item->key instanceof PhpParser\Node\Scalar\String_
                                    || $assign_var_item->key instanceof PhpParser\Node\Scalar\LNumber)
                                && isset($assign_value_atomic_type->properties[$assign_var_item->key->value])
                            ) {
                                $new_assign_type =
                                    clone $assign_value_atomic_type->properties[$assign_var_item->key->value];

                                if ($new_assign_type->possibly_undefined) {
                                    if (IssueBuffer::accepts(
                                        new PossiblyUndefinedArrayOffset(
                                            'Possibly undefined array key',
                                            new CodeLocation($statements_analyzer->getSource(), $var)
                                        ),
                                        $statements_analyzer->getSuppressedIssues()
                                    )) {
                                        // fall through
                                    }

                                    $new_assign_type->possibly_undefined = false;
                                }
                            }

                            $can_be_empty = !$assign_value_atomic_type->sealed;
                        } elseif ($assign_value_atomic_type->hasArrayAccessInterface($codebase)) {
                            ForeachAnalyzer::getKeyValueParamsForTraversableObject(
                                $assign_value_atomic_type,
                                $codebase,
                                $array_access_key_type,
                                $array_access_value_type
                            );

                            $new_assign_type = $array_access_value_type;
                        }

                        if ($already_in_scope) {
                            // removes dependennt vars from $context
                            $context->removeDescendents(
                                $list_var_id,
                                $context->vars_in_scope[$list_var_id],
                                $new_assign_type,
                                $statements_analyzer
                            );
                        }
                    }
                }

                foreach ($var_comments as $var_comment) {
                    if (!$var_comment->type) {
                        continue;
                    }

                    try {
                        if ($var_comment->var_id === $list_var_id) {
                            $var_comment_type = ExpressionAnalyzer::fleshOutType(
                                $codebase,
                                $var_comment->type,
                                $context->self,
                                $context->self,
                                $statements_analyzer->getParentFQCLN()
                            );

                            $var_comment_type->setFromDocblock();

                            $new_assign_type = $var_comment_type;
                            break;
                        }
                    } catch (\UnexpectedValueException $e) {
                        if (IssueBuffer::accepts(
                            new InvalidDocblock(
                                (string)$e->getMessage(),
                                new CodeLocation($statements_analyzer->getSource(), $assign_var)
                            )
                        )) {
                            // fall through
                        }
                    }
                }

                if ($list_var_id) {
                    $context->vars_in_scope[$list_var_id] = $new_assign_type ?: Type::getMixed();

                    if ($context->error_suppressing && ($offset || $can_be_empty)) {
                        $context->vars_in_scope[$list_var_id]->addType(new Type\Atomic\TNull);
                    }
                }
            }
        } elseif ($assign_var instanceof PhpParser\Node\Expr\ArrayDimFetch) {
            ArrayAssignmentAnalyzer::analyze(
                $statements_analyzer,
                $assign_var,
                $context,
                $assign_value,
                $assign_value_type
            );
        } elseif ($assign_var instanceof PhpParser\Node\Expr\PropertyFetch) {
            if (!$assign_var->name instanceof PhpParser\Node\Identifier) {
                // this can happen when the user actually means to type $this-><autocompleted>, but there's
                // a variable on the next line
                if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_var->var, $context) === false) {
                    return false;
                }

                if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_var->name, $context) === false) {
                    return false;
                }
            }

            if ($assign_var->name instanceof PhpParser\Node\Identifier) {
                $prop_name = $assign_var->name->name;
            } elseif (($assign_var_name_type = $statements_analyzer->node_data->getType($assign_var->name))
                && $assign_var_name_type->isSingleStringLiteral()
            ) {
                $prop_name = $assign_var_name_type->getSingleStringLiteral()->value;
            } else {
                $prop_name = null;
            }

            if ($prop_name) {
                PropertyAssignmentAnalyzer::analyzeInstance(
                    $statements_analyzer,
                    $assign_var,
                    $prop_name,
                    $assign_value,
                    $assign_value_type,
                    $context
                );
            } else {
                if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_var->var, $context) === false) {
                    return false;
                }

                if (($assign_var_type = $statements_analyzer->node_data->getType($assign_var->var))
                    && !$context->ignore_variable_property
                ) {
                    $stmt_var_type = $assign_var_type;

                    if ($stmt_var_type->hasObjectType()) {
                        foreach ($stmt_var_type->getAtomicTypes() as $type) {
                            if ($type instanceof Type\Atomic\TNamedObject) {
                                $codebase->analyzer->addMixedMemberName(
                                    strtolower($type->value) . '::$',
                                    $context->calling_function_id ?: $statements_analyzer->getFileName()
                                );
                            }
                        }
                    }
                }
            }

            if ($var_id) {
                $context->vars_possibly_in_scope[$var_id] = true;
            }

            $method_pure_compatible = $statements_analyzer->node_data->isPureCompatible($assign_var->var);

            if (($context->mutation_free || $context->external_mutation_free)
                && !$method_pure_compatible
                && !$context->collect_mutations
                && !$context->collect_initializations
            ) {
                if (IssueBuffer::accepts(
                    new ImpurePropertyAssignment(
                        'Cannot assign to a property from a mutation-free context',
                        new CodeLocation($statements_analyzer, $assign_var)
                    ),
                    $statements_analyzer->getSuppressedIssues()
                )) {
                    // fall through
                }
            }
        } elseif ($assign_var instanceof PhpParser\Node\Expr\StaticPropertyFetch &&
            $assign_var->class instanceof PhpParser\Node\Name
        ) {
            if (ExpressionAnalyzer::analyze($statements_analyzer, $assign_var, $context) === false) {
                return false;
            }

            if ($context->check_classes) {
                PropertyAssignmentAnalyzer::analyzeStatic(
                    $statements_analyzer,
                    $assign_var,
                    $assign_value,
                    $assign_value_type,
                    $context
                );
            }

            if ($var_id) {
                $context->vars_possibly_in_scope[$var_id] = true;
            }
        }

        if ($var_id && isset($context->vars_in_scope[$var_id])) {
            if ($context->vars_in_scope[$var_id]->isVoid()) {
                if (IssueBuffer::accepts(
                    new AssignmentToVoid(
                        'Cannot assign ' . $var_id . ' to type void',
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    ),
                    $statements_analyzer->getSuppressedIssues()
                )) {
                    // fall through
                }

                $context->vars_in_scope[$var_id] = Type::getNull();

                if (!$was_in_assignment) {
                    $context->inside_assignment = false;
                }

                return $context->vars_in_scope[$var_id];
            }

            if ($context->vars_in_scope[$var_id]->isNever()) {
                if (IssueBuffer::accepts(
                    new NoValue(
                        'This function or method call never returns output',
                        new CodeLocation($statements_analyzer->getSource(), $assign_var)
                    ),
                    $statements_analyzer->getSuppressedIssues()
                )) {
                    return false;
                }

                $context->vars_in_scope[$var_id] = Type::getEmpty();

                if (!$was_in_assignment) {
                    $context->inside_assignment = false;
                }

                return $context->vars_in_scope[$var_id];
            }

            if ($remove_taint && $context->vars_in_scope[$var_id]->sources) {
                $context->vars_in_scope[$var_id]->sources = null;

                $context->vars_in_scope[$var_id]->tainted = null;
            }
        }

        if (!$was_in_assignment) {
            $context->inside_assignment = false;
        }

        return $assign_value_type;
    }

    /**
     * @param   StatementsAnalyzer               $statements_analyzer
     * @param   PhpParser\Node\Expr\AssignOp    $stmt
     * @param   Context                         $context
     *
     * @return  false|null
     */
    public static function analyzeAssignmentOperation(
        StatementsAnalyzer $statements_analyzer,
        PhpParser\Node\Expr\AssignOp $stmt,
        Context $context
    ) {
        $was_in_assignment = $context->inside_assignment;

        $context->inside_assignment = true;

        if (ExpressionAnalyzer::analyze($statements_analyzer, $stmt->var, $context) === false) {
            return false;
        }

        if (ExpressionAnalyzer::analyze($statements_analyzer, $stmt->expr, $context) === false) {
            return false;
        }

        $array_var_id = ExpressionAnalyzer::getArrayVarId(
            $stmt->var,
            $statements_analyzer->getFQCLN(),
            $statements_analyzer
        );

        if ($array_var_id
            && $context->mutation_free
            && $stmt->var instanceof PhpParser\Node\Expr\PropertyFetch
            && ($stmt_var_var_type = $statements_analyzer->node_data->getType($stmt->var->var))
            && (!$stmt_var_var_type->external_mutation_free
                || $stmt_var_var_type->mutation_free)
        ) {
            if (IssueBuffer::accepts(
                new ImpurePropertyAssignment(
                    'Cannot assign to a property from a mutation-free context',
                    new CodeLocation($statements_analyzer, $stmt->var)
                ),
                $statements_analyzer->getSuppressedIssues()
            )) {
                // fall through
            }
        }

        if ($array_var_id) {
            $context->assigned_var_ids[$array_var_id] = true;
            $context->possibly_assigned_var_ids[$array_var_id] = true;

            if ($context->collect_references && $stmt->var instanceof PhpParser\Node\Expr\Variable) {
                $location = new CodeLocation($statements_analyzer, $stmt->var);
                $statements_analyzer->registerVariableAssignment(
                    $array_var_id,
                    $location
                );
                $context->unreferenced_vars[$array_var_id] = [$location->getHash() => $location];
            }
        }

        $stmt_var_type = $statements_analyzer->node_data->getType($stmt->var);
        $stmt_var_type = $stmt_var_type ? clone $stmt_var_type: null;

        $stmt_expr_type = $statements_analyzer->node_data->getType($stmt->expr);
        $result_type = null;

        if ($stmt instanceof PhpParser\Node\Expr\AssignOp\Plus
            || $stmt instanceof PhpParser\Node\Expr\AssignOp\Minus
            || $stmt instanceof PhpParser\Node\Expr\AssignOp\Mod
            || $stmt instanceof PhpParser\Node\Expr\AssignOp\Mul
            || $stmt instanceof PhpParser\Node\Expr\AssignOp\Pow
        ) {
            BinaryOpAnalyzer::analyzeNonDivArithmeticOp(
                $statements_analyzer,
                $statements_analyzer->node_data,
                $stmt->var,
                $stmt->expr,
                $stmt,
                $result_type,
                $context
            );

            if ($stmt->var instanceof PhpParser\Node\Expr\ArrayDimFetch) {
                ArrayAssignmentAnalyzer::analyze(
                    $statements_analyzer,
                    $stmt->var,
                    $context,
                    $stmt->expr,
                    $result_type ?: Type::getMixed($context->inside_loop)
                );
            } elseif ($result_type && $array_var_id) {
                $context->vars_in_scope[$array_var_id] = $result_type;
                $statements_analyzer->node_data->setType($stmt, clone $context->vars_in_scope[$array_var_id]);
            }
        } elseif ($stmt instanceof PhpParser\Node\Expr\AssignOp\Div
            && $stmt_var_type
            && $stmt_expr_type
            && $stmt_var_type->hasDefinitelyNumericType()
            && $stmt_expr_type->hasDefinitelyNumericType()
            && $array_var_id
        ) {
            $context->vars_in_scope[$array_var_id] = Type::combineUnionTypes(Type::getFloat(), Type::getInt());
            $statements_analyzer->node_data->setType($stmt, clone $context->vars_in_scope[$array_var_id]);
        } elseif ($stmt instanceof PhpParser\Node\Expr\AssignOp\Concat) {
            BinaryOpAnalyzer::analyzeConcatOp(
                $statements_analyzer,
                $stmt->var,
                $stmt->expr,
                $context,
                $result_type
            );

            if ($result_type && $array_var_id) {
                $context->vars_in_scope[$array_var_id] = $result_type;
                $statements_analyzer->node_data->setType($stmt, clone $context->vars_in_scope[$array_var_id]);
            }
        } elseif ($stmt_var_type
            && $stmt_expr_type
            && ($stmt_var_type->hasInt() || $stmt_expr_type->hasInt())
            && ($stmt instanceof PhpParser\Node\Expr\AssignOp\BitwiseOr
                || $stmt instanceof PhpParser\Node\Expr\AssignOp\BitwiseXor
                || $stmt instanceof PhpParser\Node\Expr\AssignOp\BitwiseAnd
                || $stmt instanceof PhpParser\Node\Expr\AssignOp\ShiftLeft
                || $stmt instanceof PhpParser\Node\Expr\AssignOp\ShiftRight
            )
        ) {
            BinaryOpAnalyzer::analyzeNonDivArithmeticOp(
                $statements_analyzer,
                $statements_analyzer->node_data,
                $stmt->var,
                $stmt->expr,
                $stmt,
                $result_type,
                $context
            );

            if ($result_type && $array_var_id) {
                $context->vars_in_scope[$array_var_id] = $result_type;
                $statements_analyzer->node_data->setType($stmt, clone $context->vars_in_scope[$array_var_id]);
            }
        }

        if ($array_var_id && isset($context->vars_in_scope[$array_var_id])) {
            if ($result_type && $context->vars_in_scope[$array_var_id]->by_ref) {
                $result_type->by_ref = true;
            }

            // removes dependent vars from $context
            $context->removeDescendents(
                $array_var_id,
                $context->vars_in_scope[$array_var_id],
                $result_type,
                $statements_analyzer
            );
        } else {
            $root_var_id = ExpressionAnalyzer::getRootVarId(
                $stmt->var,
                $statements_analyzer->getFQCLN(),
                $statements_analyzer
            );

            if ($root_var_id && isset($context->vars_in_scope[$root_var_id])) {
                $context->removeVarFromConflictingClauses(
                    $root_var_id,
                    $context->vars_in_scope[$root_var_id],
                    $statements_analyzer
                );
            }
        }

        if ($stmt->var instanceof PhpParser\Node\Expr\ArrayDimFetch) {
            ArrayAssignmentAnalyzer::analyze(
                $statements_analyzer,
                $stmt->var,
                $context,
                null,
                $result_type ?: Type::getEmpty()
            );
        }

        if ($stmt instanceof PhpParser\Node\Expr\AssignOp\Coalesce) {
            $old_data_provider = $statements_analyzer->node_data;

            $statements_analyzer->node_data = clone $statements_analyzer->node_data;

            $fake_coalesce_expr = new PhpParser\Node\Expr\BinaryOp\Coalesce(
                $stmt->var,
                $stmt->expr,
                $stmt->getAttributes()
            );

            if (BinaryOpAnalyzer::analyze(
                $statements_analyzer,
                $fake_coalesce_expr,
                $context
            ) === false) {
                return false;
            }

            $fake_coalesce_type = $statements_analyzer->node_data->getType($fake_coalesce_expr);

            $statements_analyzer->node_data = $old_data_provider;

            if ($fake_coalesce_type) {
                if ($array_var_id) {
                    $context->vars_in_scope[$array_var_id] = $fake_coalesce_type;
                }

                $statements_analyzer->node_data->setType($stmt, $fake_coalesce_type);
            }
        }

        if (!$was_in_assignment) {
            $context->inside_assignment = false;
        }

        return null;
    }

    /**
     * @param   StatementsAnalyzer               $statements_analyzer
     * @param   PhpParser\Node\Expr\AssignRef   $stmt
     * @param   Context                         $context
     *
     * @return  false|null
     */
    public static function analyzeAssignmentRef(
        StatementsAnalyzer $statements_analyzer,
        PhpParser\Node\Expr\AssignRef $stmt,
        Context $context
    ) {
        $assignment_type = self::analyze(
            $statements_analyzer,
            $stmt->var,
            $stmt->expr,
            null,
            $context,
            $stmt->getDocComment()
        );
        if ($assignment_type === false) {
            return false;
        }

        $assignment_type->by_ref = true;

        $lhs_var_id = ExpressionAnalyzer::getVarId(
            $stmt->var,
            $statements_analyzer->getFQCLN(),
            $statements_analyzer
        );

        $rhs_var_id = ExpressionAnalyzer::getVarId(
            $stmt->expr,
            $statements_analyzer->getFQCLN(),
            $statements_analyzer
        );

        if ($lhs_var_id) {
            $context->vars_in_scope[$lhs_var_id] = $assignment_type;
            $context->hasVariable($lhs_var_id, $statements_analyzer);
        }

        if ($rhs_var_id && !isset($context->vars_in_scope[$rhs_var_id])) {
            $context->vars_in_scope[$rhs_var_id] = Type::getMixed();
        }
    }
}
