// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file implements the Check function, which drives type-checking.

package types

import (
	
	
	
	
	
)

// debugging/development support
const (
	debug = false // leave on during development
	trace = false // turn on for detailed type resolution traces

	// TODO(rfindley): add compiler error message handling from types2, guarded
	// behind this flag, so that we can keep the code in sync.
	compilerErrorMessages = false // match compiler error messages
)

// exprInfo stores information about an untyped expression.
type exprInfo struct {
	isLhs bool // expression is lhs operand of a shift with delayed type-check
	mode  operandMode
	typ   *Basic
	val   constant.Value // constant value; or nil (if not a constant)
}

// An environment represents the environment within which an object is
// type-checked.
type environment struct {
	decl          *declInfo              // package-level declaration whose init expression/function body is checked
	scope         *Scope                 // top-most scope for lookups
	pos           token.Pos              // if valid, identifiers are looked up as if at position pos (used by Eval)
	iota          constant.Value         // value of iota in a constant declaration; nil otherwise
	errpos        positioner             // if set, identifier position of a constant with inherited initializer
	inTParamList  bool                   // set if inside a type parameter list
	sig           *Signature             // function signature if inside a function; nil otherwise
	isPanic       map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
	hasLabel      bool                   // set if a function makes use of labels (only ~1% of functions); unused outside functions
	hasCallOrRecv bool                   // set if an expression contains a function call or channel receive operation
}

// lookup looks up name in the current environment and returns the matching object, or nil.
func ( *environment) ( string) Object {
	,  := .scope.LookupParent(, .pos)
	return 
}

// An importKey identifies an imported package by import path and source directory
// (directory containing the file containing the import). In practice, the directory
// may always be the same, or may not matter. Given an (import path, directory), an
// importer must always return the same package (but given two different import paths,
// an importer may still return the same package by mapping them to the same package
// paths).
type importKey struct {
	path, dir string
}

// A dotImportKey describes a dot-imported object in the given scope.
type dotImportKey struct {
	scope *Scope
	name  string
}

// An action describes a (delayed) action.
type action struct {
	f    func()      // action to be executed
	desc *actionDesc // action description; may be nil, requires debug to be set
}

// If debug is set, describef sets a printf-formatted description for action a.
// Otherwise, it is a no-op.
func ( *action) ( positioner,  string,  ...any) {
	if debug {
		.desc = &actionDesc{, , }
	}
}

// An actionDesc provides information on an action.
// For debugging only.
type actionDesc struct {
	pos    positioner
	format string
	args   []any
}

// A Checker maintains the state of the type checker.
// It must be created with NewChecker.
type Checker struct {
	// package information
	// (initialized by NewChecker, valid for the life-time of checker)
	conf *Config
	ctxt *Context // context for de-duplicating instances
	fset *token.FileSet
	pkg  *Package
	*Info
	version version                // accepted language version
	nextID  uint64                 // unique Id for type parameters (first valid Id is 1)
	objMap  map[Object]*declInfo   // maps package-level objects and (non-interface) methods to declaration info
	impMap  map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
	valids  instanceLookup         // valid *Named (incl. instantiated) types per the validType check

	// pkgPathMap maps package names to the set of distinct import paths we've
	// seen for that name, anywhere in the import graph. It is used for
	// disambiguating package names in error messages.
	//
	// pkgPathMap is allocated lazily, so that we don't pay the price of building
	// it on the happy path. seenPkgMap tracks the packages that we've already
	// walked.
	pkgPathMap map[string]map[string]bool
	seenPkgMap map[*Package]bool

	// information collected during type-checking of a set of package files
	// (initialized by Files, valid only for the duration of check.Files;
	// maps and lists are allocated on demand)
	files         []*ast.File               // package files
	imports       []*PkgName                // list of imported packages
	dotImportMap  map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
	recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
	brokenAliases map[*TypeName]bool        // set of aliases with broken (not yet determined) types
	unionTypeSets map[*Union]*_TypeSet      // computed type sets for union types
	mono          monoGraph                 // graph for detecting non-monomorphizable instantiation loops

	firstErr error                 // first error encountered
	methods  map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
	untyped  map[ast.Expr]exprInfo // map of expressions without final type
	delayed  []action              // stack of delayed action segments; segments are processed in FIFO order
	objPath  []Object              // path of object dependencies during type inference (for cycle reporting)
	cleaners []cleaner             // list of types that may need a final cleanup at the end of type-checking

	// environment within which the current object is type-checked (valid only
	// for the duration of type-checking a specific object)
	environment

	// debugging
	indent int // indentation for tracing
}

// addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
func ( *Checker) ( Object) {
	 := .decl
	if  == nil {
		return // not in a package-level init expression
	}
	if ,  := .objMap[]; ! {
		return // to is not a package-level object
	}
	.addDep()
}

// brokenAlias records that alias doesn't have a determined type yet.
// It also sets alias.typ to Typ[Invalid].
func ( *Checker) ( *TypeName) {
	if .brokenAliases == nil {
		.brokenAliases = make(map[*TypeName]bool)
	}
	.brokenAliases[] = true
	.typ = Typ[Invalid]
}

// validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
func ( *Checker) ( *TypeName,  Type) {
	delete(.brokenAliases, )
	.typ = 
}

// isBrokenAlias reports whether alias doesn't have a determined type yet.
func ( *Checker) ( *TypeName) bool {
	return .typ == Typ[Invalid] && .brokenAliases[]
}

func ( *Checker) ( ast.Expr,  bool,  operandMode,  *Basic,  constant.Value) {
	 := .untyped
	if  == nil {
		 = make(map[ast.Expr]exprInfo)
		.untyped = 
	}
	[] = exprInfo{, , , }
}

// later pushes f on to the stack of actions that will be processed later;
// either at the end of the current statement, or in case of a local constant
// or variable declaration, before the constant or variable is in scope
// (so that f still sees the scope before any new declarations).
// later returns the pushed action so one can provide a description
// via action.describef for debugging, if desired.
func ( *Checker) ( func()) *action {
	 := len(.delayed)
	.delayed = append(.delayed, action{f: })
	return &.delayed[]
}

// push pushes obj onto the object path and returns its index in the path.
func ( *Checker) ( Object) int {
	.objPath = append(.objPath, )
	return len(.objPath) - 1
}

// pop pops and returns the topmost object from the object path.
func ( *Checker) () Object {
	 := len(.objPath) - 1
	 := .objPath[]
	.objPath[] = nil
	.objPath = .objPath[:]
	return 
}

type cleaner interface {
	cleanup()
}

// needsCleanup records objects/types that implement the cleanup method
// which will be called at the end of type-checking.
func ( *Checker) ( cleaner) {
	.cleaners = append(.cleaners, )
}

// NewChecker returns a new Checker instance for a given package.
// Package files may be added incrementally via checker.Files.
func ( *Config,  *token.FileSet,  *Package,  *Info) *Checker {
	// make sure we have a configuration
	if  == nil {
		 = new(Config)
	}

	// make sure we have an info struct
	if  == nil {
		 = new(Info)
	}

	,  := parseGoVersion(.GoVersion)
	if  != nil {
		panic(fmt.Sprintf("invalid Go version %q (%v)", .GoVersion, ))
	}

	return &Checker{
		conf:    ,
		ctxt:    .Context,
		fset:    ,
		pkg:     ,
		Info:    ,
		version: ,
		objMap:  make(map[Object]*declInfo),
		impMap:  make(map[importKey]*Package),
	}
}

// initFiles initializes the files-specific portion of checker.
// The provided files must all belong to the same package.
func ( *Checker) ( []*ast.File) {
	// start with a clean slate (check.Files may be called multiple times)
	.files = nil
	.imports = nil
	.dotImportMap = nil

	.firstErr = nil
	.methods = nil
	.untyped = nil
	.delayed = nil
	.objPath = nil
	.cleaners = nil

	// determine package name and collect valid files
	 := .pkg
	for ,  := range  {
		switch  := .Name.Name; .name {
		case "":
			if  != "_" {
				.name = 
			} else {
				.errorf(.Name, _BlankPkgName, "invalid package name _")
			}
			fallthrough

		case :
			.files = append(.files, )

		default:
			.errorf(atPos(.Package), _MismatchedPkgName, "package %s; expected %s", , .name)
			// ignore this file
		}
	}
}

// A bailout panic is used for early termination.
type bailout struct{}

func ( *Checker) ( *error) {
	switch p := recover().(type) {
	case nil, bailout:
		// normal return or early exit
		* = .firstErr
	default:
		// re-panic
		panic()
	}
}

// Files checks the provided files as part of the checker's package.
func ( *Checker) ( []*ast.File) error { return .checkFiles() }

var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")

func ( *Checker) ( []*ast.File) ( error) {
	if .conf.FakeImportC && .conf.go115UsesCgo {
		return errBadCgo
	}

	defer .handleBailout(&)

	 := func( string) {
		if trace {
			fmt.Println()
			fmt.Println()
		}
	}

	("== initFiles ==")
	.initFiles()

	("== collectObjects ==")
	.collectObjects()

	("== packageObjects ==")
	.packageObjects()

	("== processDelayed ==")
	.processDelayed(0) // incl. all functions

	("== cleanup ==")
	.cleanup()

	("== initOrder ==")
	.initOrder()

	if !.conf.DisableUnusedImportCheck {
		("== unusedImports ==")
		.unusedImports()
	}

	("== recordUntyped ==")
	.recordUntyped()

	if .firstErr == nil {
		// TODO(mdempsky): Ensure monomorph is safe when errors exist.
		.monomorph()
	}

	.pkg.complete = true

	// no longer needed - release memory
	.imports = nil
	.dotImportMap = nil
	.pkgPathMap = nil
	.seenPkgMap = nil
	.recvTParamMap = nil
	.brokenAliases = nil
	.unionTypeSets = nil
	.ctxt = nil

	// TODO(rFindley) There's more memory we should release at this point.

	return
}

// processDelayed processes all delayed actions pushed after top.
func ( *Checker) ( int) {
	// If each delayed action pushes a new action, the
	// stack will continue to grow during this loop.
	// However, it is only processing functions (which
	// are processed in a delayed fashion) that may
	// add more actions (such as nested functions), so
	// this is a sufficiently bounded process.
	for  := ;  < len(.delayed); ++ {
		 := &.delayed[]
		if trace {
			if .desc != nil {
				.trace(.desc.pos.Pos(), "-- "+.desc.format, .desc.args...)
			} else {
				.trace(token.NoPos, "-- delayed %p", .f)
			}
		}
		.f() // may append to check.delayed
		if trace {
			fmt.Println()
		}
	}
	assert( <= len(.delayed)) // stack must not have shrunk
	.delayed = .delayed[:]
}

// cleanup runs cleanup for all collected cleaners.
func ( *Checker) () {
	// Don't use a range clause since Named.cleanup may add more cleaners.
	for  := 0;  < len(.cleaners); ++ {
		.cleaners[].cleanup()
	}
	.cleaners = nil
}

func ( *Checker) ( *operand) {
	// convert x into a user-friendly set of values
	// TODO(gri) this code can be simplified
	var  Type
	var  constant.Value
	switch .mode {
	case invalid:
		 = Typ[Invalid]
	case novalue:
		 = (*Tuple)(nil)
	case constant_:
		 = .typ
		 = .val
	default:
		 = .typ
	}
	assert(.expr != nil &&  != nil)

	if isUntyped() {
		// delay type and value recording until we know the type
		// or until the end of type checking
		.rememberUntyped(.expr, false, .mode, .(*Basic), )
	} else {
		.recordTypeAndValue(.expr, .mode, , )
	}
}

func ( *Checker) () {
	if !debug && .Types == nil {
		return // nothing to do
	}

	for ,  := range .untyped {
		if debug && isTyped(.typ) {
			.dump("%v: %s (type %s) is typed", .Pos(), , .typ)
			unreachable()
		}
		.recordTypeAndValue(, .mode, .typ, .val)
	}
}

func ( *Checker) ( ast.Expr,  operandMode,  Type,  constant.Value) {
	assert( != nil)
	assert( != nil)
	if  == invalid {
		return // omit
	}
	if  == constant_ {
		assert( != nil)
		// We check allBasic(typ, IsConstType) here as constant expressions may be
		// recorded as type parameters.
		assert( == Typ[Invalid] || allBasic(, IsConstType))
	}
	if  := .Types;  != nil {
		[] = TypeAndValue{, , }
	}
}

func ( *Checker) ( ast.Expr,  *Signature) {
	// f must be a (possibly parenthesized, possibly qualified)
	// identifier denoting a built-in (including unsafe's non-constant
	// functions Add and Slice): record the signature for f and possible
	// children.
	for {
		.recordTypeAndValue(, builtin, , nil)
		switch p := .(type) {
		case *ast.Ident, *ast.SelectorExpr:
			return // we're done
		case *ast.ParenExpr:
			 = .X
		default:
			unreachable()
		}
	}
}

func ( *Checker) ( ast.Expr,  [2]Type) {
	assert( != nil)
	if [0] == nil || [1] == nil {
		return
	}
	assert(isTyped([0]) && isTyped([1]) && (isBoolean([1]) || [1] == universeError))
	if  := .Types;  != nil {
		for {
			 := []
			assert(.Type != nil) // should have been recorded already
			 := .Pos()
			.Type = NewTuple(
				NewVar(, .pkg, "", [0]),
				NewVar(, .pkg, "", [1]),
			)
			[] = 
			// if x is a parenthesized expression (p.X), update p.X
			,  := .(*ast.ParenExpr)
			if  == nil {
				break
			}
			 = .X
		}
	}
}

// recordInstance records instantiation information into check.Info, if the
// Instances map is non-nil. The given expr must be an ident, selector, or
// index (list) expr with ident or selector operand.
//
// TODO(rfindley): the expr parameter is fragile. See if we can access the
// instantiated identifier in some other way.
func ( *Checker) ( ast.Expr,  []Type,  Type) {
	 := instantiatedIdent()
	assert( != nil)
	assert( != nil)
	if  := .Instances;  != nil {
		[] = Instance{newTypeList(), }
	}
}

func instantiatedIdent( ast.Expr) *ast.Ident {
	var  ast.Expr
	switch e := .(type) {
	case *ast.IndexExpr:
		 = .X
	case *ast.IndexListExpr:
		 = .X
	case *ast.SelectorExpr, *ast.Ident:
		 = 
	}
	switch x := .(type) {
	case *ast.Ident:
		return 
	case *ast.SelectorExpr:
		return .Sel
	}
	panic("instantiated ident not found")
}

func ( *Checker) ( *ast.Ident,  Object) {
	assert( != nil)
	if  := .Defs;  != nil {
		[] = 
	}
}

func ( *Checker) ( *ast.Ident,  Object) {
	assert( != nil)
	assert( != nil)
	if  := .Uses;  != nil {
		[] = 
	}
}

func ( *Checker) ( ast.Node,  Object) {
	assert( != nil)
	assert( != nil)
	if  := .Implicits;  != nil {
		[] = 
	}
}

func ( *Checker) ( *ast.SelectorExpr,  SelectionKind,  Type,  Object,  []int,  bool) {
	assert( != nil && ( == nil || len() > 0))
	.recordUse(.Sel, )
	if  := .Selections;  != nil {
		[] = &Selection{, , , , }
	}
}

func ( *Checker) ( ast.Node,  *Scope) {
	assert( != nil)
	assert( != nil)
	if  := .Scopes;  != nil {
		[] = 
	}
}