third_party/gotools/go/types/decl.go - llvm-project/llgo - Git at Google

 // Copyright 2014 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.

 package types

 import (
 	"go/ast"
 	"go/token"

 	"llvm.org/llgo/third_party/gotools/go/exact"
 )

 func (check *Checker) reportAltDecl(obj Object) {
 	if pos := obj.Pos(); pos.IsValid() {
 		// We use "other" rather than "previous" here because
 		// the first declaration seen may not be textually
 		// earlier in the source.
 		check.errorf(pos, "\tother declaration of %s", obj.Name()) // secondary error, \t indented
 	}
 }

 func (check *Checker) declare(scope *Scope, id *ast.Ident, obj Object) {
 	// spec: "The blank identifier, represented by the underscore
 	// character _, may be used in a declaration like any other
 	// identifier but the declaration does not introduce a new
 	// binding."
 	if obj.Name() != "_" {
 		if alt := scope.Insert(obj); alt != nil {
 			check.errorf(obj.Pos(), "%s redeclared in this block", obj.Name())
 			check.reportAltDecl(alt)
 			return
 		}
 	}
 	if id != nil {
 		check.recordDef(id, obj)
 	}
 }

 // objDecl type-checks the declaration of obj in its respective (file) context.
 // See check.typ for the details on def and path.
 func (check *Checker) objDecl(obj Object, def *Named, path []*TypeName) {
 	if obj.Type() != nil {
 		return // already checked - nothing to do
 	}

 	if trace {
 		check.trace(obj.Pos(), "-- declaring %s", obj.Name())
 		check.indent++
 		defer func() {
 			check.indent--
 			check.trace(obj.Pos(), "=> %s", obj)
 		}()
 	}

 	d := check.objMap[obj]
 	if d == nil {
 		check.dump("%s: %s should have been declared", obj.Pos(), obj.Name())
 		unreachable()
 	}

 	// save/restore current context and setup object context
 	defer func(ctxt context) {
 		check.context = ctxt
 	}(check.context)
 	check.context = context{
 		scope: d.file,
 	}

 	// Const and var declarations must not have initialization
 	// cycles. We track them by remembering the current declaration
 	// in check.decl. Initialization expressions depending on other
 	// consts, vars, or functions, add dependencies to the current
 	// check.decl.
 	switch obj := obj.(type) {
 	case *Const:
 		check.decl = d // new package-level const decl
 		check.constDecl(obj, d.typ, d.init)
 	case *Var:
 		check.decl = d // new package-level var decl
 		check.varDecl(obj, d.lhs, d.typ, d.init)
 	case *TypeName:
 		// invalid recursive types are detected via path
 		check.typeDecl(obj, d.typ, def, path)
 	case *Func:
 		// functions may be recursive - no need to track dependencies
 		check.funcDecl(obj, d)
 	default:
 		unreachable()
 	}
 }

 func (check *Checker) constDecl(obj *Const, typ, init ast.Expr) {
 	assert(obj.typ == nil)

 	if obj.visited {
 		obj.typ = Typ[Invalid]
 		return
 	}
 	obj.visited = true

 	// use the correct value of iota
 	assert(check.iota == nil)
 	check.iota = obj.val
 	defer func() { check.iota = nil }()

 	// provide valid constant value under all circumstances
 	obj.val = exact.MakeUnknown()

 	// determine type, if any
 	if typ != nil {
 		t := check.typ(typ)
 		if !isConstType(t) {
 			check.errorf(typ.Pos(), "invalid constant type %s", t)
 			obj.typ = Typ[Invalid]
 			return
 		}
 		obj.typ = t
 	}

 	// check initialization
 	var x operand
 	if init != nil {
 		check.expr(&x, init)
 	}
 	check.initConst(obj, &x)
 }

 func (check *Checker) varDecl(obj *Var, lhs []*Var, typ, init ast.Expr) {
 	assert(obj.typ == nil)

 	if obj.visited {
 		obj.typ = Typ[Invalid]
 		return
 	}
 	obj.visited = true

 	// var declarations cannot use iota
 	assert(check.iota == nil)

 	// determine type, if any
 	if typ != nil {
 		obj.typ = check.typ(typ)
 	}

 	// check initialization
 	if init == nil {
 		if typ == nil {
 			// error reported before by arityMatch
 			obj.typ = Typ[Invalid]
 		}
 		return
 	}

 	if lhs == nil || len(lhs) == 1 {
 		assert(lhs == nil || lhs[0] == obj)
 		var x operand
 		check.expr(&x, init)
 		check.initVar(obj, &x, false)
 		return
 	}

 	if debug {
 		// obj must be one of lhs
 		found := false
 		for _, lhs := range lhs {
 			if obj == lhs {
 				found = true
 				break
 			}
 		}
 		if !found {
 			panic("inconsistent lhs")
 		}
 	}
 	check.initVars(lhs, []ast.Expr{init}, token.NoPos)
 }

 // underlying returns the underlying type of typ; possibly by following
 // forward chains of named types. Such chains only exist while named types
 // are incomplete.
 func underlying(typ Type) Type {
 	for {
 		n, _ := typ.(*Named)
 		if n == nil {
 			break
 		}
 		typ = n.underlying
 	}
 	return typ
 }

 func (n *Named) setUnderlying(typ Type) {
 	if n != nil {
 		n.underlying = typ
 	}
 }

 func (check *Checker) typeDecl(obj *TypeName, typ ast.Expr, def *Named, path []*TypeName) {
 	assert(obj.typ == nil)

 	// type declarations cannot use iota
 	assert(check.iota == nil)

 	named := &Named{obj: obj}
 	def.setUnderlying(named)
 	obj.typ = named // make sure recursive type declarations terminate

 	// determine underlying type of named
 	check.typExpr(typ, named, append(path, obj))

 	// The underlying type of named may be itself a named type that is
 	// incomplete:
 	//
 	//	type (
 	//		A B
 	//		B *C
 	//		C A
 	//	)
 	//
 	// The type of C is the (named) type of A which is incomplete,
 	// and which has as its underlying type the named type B.
 	// Determine the (final, unnamed) underlying type by resolving
 	// any forward chain (they always end in an unnamed type).
 	named.underlying = underlying(named.underlying)

 	// check and add associated methods
 	// TODO(gri) It's easy to create pathological cases where the
 	// current approach is incorrect: In general we need to know
 	// and add all methods _before_ type-checking the type.
 	// See http://play.golang.org/p/WMpE0q2wK8
 	check.addMethodDecls(obj)
 }

 func (check *Checker) addMethodDecls(obj *TypeName) {
 	// get associated methods
 	methods := check.methods[obj.name]
 	if len(methods) == 0 {
 		return // no methods
 	}
 	delete(check.methods, obj.name)

 	// use an objset to check for name conflicts
 	var mset objset

 	// spec: "If the base type is a struct type, the non-blank method
 	// and field names must be distinct."
 	base := obj.typ.(*Named)
 	if t, _ := base.underlying.(*Struct); t != nil {
 		for _, fld := range t.fields {
 			if fld.name != "_" {
 				assert(mset.insert(fld) == nil)
 			}
 		}
 	}

 	// Checker.Files may be called multiple times; additional package files
 	// may add methods to already type-checked types. Add pre-existing methods
 	// so that we can detect redeclarations.
 	for _, m := range base.methods {
 		assert(m.name != "_")
 		assert(mset.insert(m) == nil)
 	}

 	// type-check methods
 	for _, m := range methods {
 		// spec: "For a base type, the non-blank names of methods bound
 		// to it must be unique."
 		if m.name != "_" {
 			if alt := mset.insert(m); alt != nil {
 				switch alt.(type) {
 				case *Var:
 					check.errorf(m.pos, "field and method with the same name %s", m.name)
 				case *Func:
 					check.errorf(m.pos, "method %s already declared for %s", m.name, base)
 				default:
 					unreachable()
 				}
 				check.reportAltDecl(alt)
 				continue
 			}
 		}
 		check.objDecl(m, nil, nil)
 		// methods with blank _ names cannot be found - don't keep them
 		if m.name != "_" {
 			base.methods = append(base.methods, m)
 		}
 	}
 }

 func (check *Checker) funcDecl(obj *Func, decl *declInfo) {
 	assert(obj.typ == nil)

 	// func declarations cannot use iota
 	assert(check.iota == nil)

 	sig := new(Signature)
 	obj.typ = sig // guard against cycles
 	fdecl := decl.fdecl
 	check.funcType(sig, fdecl.Recv, fdecl.Type)
 	if sig.recv == nil && obj.name == "init" && (sig.params.Len() > 0 || sig.results.Len() > 0) {
 		check.errorf(fdecl.Pos(), "func init must have no arguments and no return values")
 		// ok to continue
 	}

 	// function body must be type-checked after global declarations
 	// (functions implemented elsewhere have no body)
 	if !check.conf.IgnoreFuncBodies && fdecl.Body != nil {
 		check.later(obj.name, decl, sig, fdecl.Body)
 	}
 }

 func (check *Checker) declStmt(decl ast.Decl) {
 	pkg := check.pkg

 	switch d := decl.(type) {
 	case *ast.BadDecl:
 		// ignore

 	case *ast.GenDecl:
 		var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
 		for iota, spec := range d.Specs {
 			switch s := spec.(type) {
 			case *ast.ValueSpec:
 				switch d.Tok {
 				case token.CONST:
 					// determine which init exprs to use
 					switch {
 					case s.Type != nil || len(s.Values) > 0:
 						last = s
 					case last == nil:
 						last = new(ast.ValueSpec) // make sure last exists
 					}

 					// declare all constants
 					lhs := make([]*Const, len(s.Names))
 					for i, name := range s.Names {
 						obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))
 						lhs[i] = obj

 						var init ast.Expr
 						if i < len(last.Values) {
 							init = last.Values[i]
 						}

 						check.constDecl(obj, last.Type, init)
 					}

 					check.arityMatch(s, last)

 					for i, name := range s.Names {
 						check.declare(check.scope, name, lhs[i])
 					}

 				case token.VAR:
 					lhs0 := make([]*Var, len(s.Names))
 					for i, name := range s.Names {
 						lhs0[i] = NewVar(name.Pos(), pkg, name.Name, nil)
 					}

 					// initialize all variables
 					for i, obj := range lhs0 {
 						var lhs []*Var
 						var init ast.Expr
 						switch len(s.Values) {
 						case len(s.Names):
 							// lhs and rhs match
 							init = s.Values[i]
 						case 1:
 							// rhs is expected to be a multi-valued expression
 							lhs = lhs0
 							init = s.Values[0]
 						default:
 							if i < len(s.Values) {
 								init = s.Values[i]
 							}
 						}
 						check.varDecl(obj, lhs, s.Type, init)
 						if len(s.Values) == 1 {
 							// If we have a single lhs variable we are done either way.
 							// If we have a single rhs expression, it must be a multi-
 							// valued expression, in which case handling the first lhs
 							// variable will cause all lhs variables to have a type
 							// assigned, and we are done as well.
 							if debug {
 								for _, obj := range lhs0 {
 									assert(obj.typ != nil)
 								}
 							}
 							break
 						}
 					}

 					check.arityMatch(s, nil)

 					// declare all variables
 					// (only at this point are the variable scopes (parents) set)
 					for i, name := range s.Names {
 						check.declare(check.scope, name, lhs0[i])
 					}

 				default:
 					check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
 				}

 			case *ast.TypeSpec:
 				obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
 				check.declare(check.scope, s.Name, obj)
 				check.typeDecl(obj, s.Type, nil, nil)

 			default:
 				check.invalidAST(s.Pos(), "const, type, or var declaration expected")
 			}
 		}

 	default:
 		check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
 	}
 }
	// Copyright 2014 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.

	package types

	import (
	"go/ast"
	"go/token"

	"llvm.org/llgo/third_party/gotools/go/exact"
	)

	func (check *Checker) reportAltDecl(obj Object) {
	if pos := obj.Pos(); pos.IsValid() {
	// We use "other" rather than "previous" here because
	// the first declaration seen may not be textually
	// earlier in the source.
	check.errorf(pos, "\tother declaration of %s", obj.Name()) // secondary error, \t indented
	}
	}

	func (check Checker) declare(scope Scope, id *ast.Ident, obj Object) {
	// spec: "The blank identifier, represented by the underscore
	// character _, may be used in a declaration like any other
	// identifier but the declaration does not introduce a new
	// binding."
	if obj.Name() != "_" {
	if alt := scope.Insert(obj); alt != nil {
	check.errorf(obj.Pos(), "%s redeclared in this block", obj.Name())
	check.reportAltDecl(alt)
	return
	}
	}
	if id != nil {
	check.recordDef(id, obj)
	}
	}

	// objDecl type-checks the declaration of obj in its respective (file) context.
	// See check.typ for the details on def and path.
	func (check Checker) objDecl(obj Object, def Named, path []*TypeName) {
	if obj.Type() != nil {
	return // already checked - nothing to do
	}

	if trace {
	check.trace(obj.Pos(), "-- declaring %s", obj.Name())
	check.indent++
	defer func() {
	check.indent--
	check.trace(obj.Pos(), "=> %s", obj)
	}()
	}

	d := check.objMap[obj]
	if d == nil {
	check.dump("%s: %s should have been declared", obj.Pos(), obj.Name())
	unreachable()
	}

	// save/restore current context and setup object context
	defer func(ctxt context) {
	check.context = ctxt
	}(check.context)
	check.context = context{
	scope: d.file,
	}

	// Const and var declarations must not have initialization
	// cycles. We track them by remembering the current declaration
	// in check.decl. Initialization expressions depending on other
	// consts, vars, or functions, add dependencies to the current
	// check.decl.
	switch obj := obj.(type) {
	case *Const:
	check.decl = d // new package-level const decl
	check.constDecl(obj, d.typ, d.init)
	case *Var:
	check.decl = d // new package-level var decl
	check.varDecl(obj, d.lhs, d.typ, d.init)
	case *TypeName:
	// invalid recursive types are detected via path
	check.typeDecl(obj, d.typ, def, path)
	case *Func:
	// functions may be recursive - no need to track dependencies
	check.funcDecl(obj, d)
	default:
	unreachable()
	}
	}

	func (check Checker) constDecl(obj Const, typ, init ast.Expr) {
	assert(obj.typ == nil)

	if obj.visited {
	obj.typ = Typ[Invalid]
	return
	}
	obj.visited = true

	// use the correct value of iota
	assert(check.iota == nil)
	check.iota = obj.val
	defer func() { check.iota = nil }()

	// provide valid constant value under all circumstances
	obj.val = exact.MakeUnknown()

	// determine type, if any
	if typ != nil {
	t := check.typ(typ)
	if !isConstType(t) {
	check.errorf(typ.Pos(), "invalid constant type %s", t)
	obj.typ = Typ[Invalid]
	return
	}
	obj.typ = t
	}

	// check initialization
	var x operand
	if init != nil {
	check.expr(&x, init)
	}
	check.initConst(obj, &x)
	}

	func (check Checker) varDecl(obj Var, lhs []*Var, typ, init ast.Expr) {
	assert(obj.typ == nil)

	if obj.visited {
	obj.typ = Typ[Invalid]
	return
	}
	obj.visited = true

	// var declarations cannot use iota
	assert(check.iota == nil)

	// determine type, if any
	if typ != nil {
	obj.typ = check.typ(typ)
	}

	// check initialization
	if init == nil {
	if typ == nil {
	// error reported before by arityMatch
	obj.typ = Typ[Invalid]
	}
	return
	}

	if lhs == nil \|\| len(lhs) == 1 {
	assert(lhs == nil \|\| lhs[0] == obj)
	var x operand
	check.expr(&x, init)
	check.initVar(obj, &x, false)
	return
	}

	if debug {
	// obj must be one of lhs
	found := false
	for _, lhs := range lhs {
	if obj == lhs {
	found = true
	break
	}
	}
	if !found {
	panic("inconsistent lhs")
	}
	}
	check.initVars(lhs, []ast.Expr{init}, token.NoPos)
	}

	// underlying returns the underlying type of typ; possibly by following
	// forward chains of named types. Such chains only exist while named types
	// are incomplete.
	func underlying(typ Type) Type {
	for {
	n, _ := typ.(*Named)
	if n == nil {
	break
	}
	typ = n.underlying
	}
	return typ
	}

	func (n *Named) setUnderlying(typ Type) {
	if n != nil {
	n.underlying = typ
	}
	}

	func (check Checker) typeDecl(obj TypeName, typ ast.Expr, def Named, path []TypeName) {
	assert(obj.typ == nil)

	// type declarations cannot use iota
	assert(check.iota == nil)

	named := &Named{obj: obj}
	def.setUnderlying(named)
	obj.typ = named // make sure recursive type declarations terminate

	// determine underlying type of named
	check.typExpr(typ, named, append(path, obj))

	// The underlying type of named may be itself a named type that is
	// incomplete:
	//
	// type (
	// A B
	// B *C
	// C A
	// )
	//
	// The type of C is the (named) type of A which is incomplete,
	// and which has as its underlying type the named type B.
	// Determine the (final, unnamed) underlying type by resolving
	// any forward chain (they always end in an unnamed type).
	named.underlying = underlying(named.underlying)

	// check and add associated methods
	// TODO(gri) It's easy to create pathological cases where the
	// current approach is incorrect: In general we need to know
	// and add all methods _before_ type-checking the type.
	// See http://play.golang.org/p/WMpE0q2wK8
	check.addMethodDecls(obj)
	}

	func (check Checker) addMethodDecls(obj TypeName) {
	// get associated methods
	methods := check.methods[obj.name]
	if len(methods) == 0 {
	return // no methods
	}
	delete(check.methods, obj.name)

	// use an objset to check for name conflicts
	var mset objset

	// spec: "If the base type is a struct type, the non-blank method
	// and field names must be distinct."
	base := obj.typ.(*Named)
	if t, _ := base.underlying.(*Struct); t != nil {
	for _, fld := range t.fields {
	if fld.name != "_" {
	assert(mset.insert(fld) == nil)
	}
	}
	}

	// Checker.Files may be called multiple times; additional package files
	// may add methods to already type-checked types. Add pre-existing methods
	// so that we can detect redeclarations.
	for _, m := range base.methods {
	assert(m.name != "_")
	assert(mset.insert(m) == nil)
	}

	// type-check methods
	for _, m := range methods {
	// spec: "For a base type, the non-blank names of methods bound
	// to it must be unique."
	if m.name != "_" {
	if alt := mset.insert(m); alt != nil {
	switch alt.(type) {
	case *Var:
	check.errorf(m.pos, "field and method with the same name %s", m.name)
	case *Func:
	check.errorf(m.pos, "method %s already declared for %s", m.name, base)
	default:
	unreachable()
	}
	check.reportAltDecl(alt)
	continue
	}
	}
	check.objDecl(m, nil, nil)
	// methods with blank _ names cannot be found - don't keep them
	if m.name != "_" {
	base.methods = append(base.methods, m)
	}
	}
	}

	func (check Checker) funcDecl(obj Func, decl *declInfo) {
	assert(obj.typ == nil)

	// func declarations cannot use iota
	assert(check.iota == nil)

	sig := new(Signature)
	obj.typ = sig // guard against cycles
	fdecl := decl.fdecl
	check.funcType(sig, fdecl.Recv, fdecl.Type)
	if sig.recv == nil && obj.name == "init" && (sig.params.Len() > 0 \|\| sig.results.Len() > 0) {
	check.errorf(fdecl.Pos(), "func init must have no arguments and no return values")
	// ok to continue
	}

	// function body must be type-checked after global declarations
	// (functions implemented elsewhere have no body)
	if !check.conf.IgnoreFuncBodies && fdecl.Body != nil {
	check.later(obj.name, decl, sig, fdecl.Body)
	}
	}

	func (check *Checker) declStmt(decl ast.Decl) {
	pkg := check.pkg

	switch d := decl.(type) {
	case *ast.BadDecl:
	// ignore

	case *ast.GenDecl:
	var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
	for iota, spec := range d.Specs {
	switch s := spec.(type) {
	case *ast.ValueSpec:
	switch d.Tok {
	case token.CONST:
	// determine which init exprs to use
	switch {
	case s.Type != nil \|\| len(s.Values) > 0:
	last = s
	case last == nil:
	last = new(ast.ValueSpec) // make sure last exists
	}

	// declare all constants
	lhs := make([]*Const, len(s.Names))
	for i, name := range s.Names {
	obj := NewConst(name.Pos(), pkg, name.Name, nil, exact.MakeInt64(int64(iota)))
	lhs[i] = obj

	var init ast.Expr
	if i < len(last.Values) {
	init = last.Values[i]
	}

	check.constDecl(obj, last.Type, init)
	}

	check.arityMatch(s, last)

	for i, name := range s.Names {
	check.declare(check.scope, name, lhs[i])
	}

	case token.VAR:
	lhs0 := make([]*Var, len(s.Names))
	for i, name := range s.Names {
	lhs0[i] = NewVar(name.Pos(), pkg, name.Name, nil)
	}

	// initialize all variables
	for i, obj := range lhs0 {
	var lhs []*Var
	var init ast.Expr
	switch len(s.Values) {
	case len(s.Names):
	// lhs and rhs match
	init = s.Values[i]
	case 1:
	// rhs is expected to be a multi-valued expression
	lhs = lhs0
	init = s.Values[0]
	default:
	if i < len(s.Values) {
	init = s.Values[i]
	}
	}
	check.varDecl(obj, lhs, s.Type, init)
	if len(s.Values) == 1 {
	// If we have a single lhs variable we are done either way.
	// If we have a single rhs expression, it must be a multi-
	// valued expression, in which case handling the first lhs
	// variable will cause all lhs variables to have a type
	// assigned, and we are done as well.
	if debug {
	for _, obj := range lhs0 {
	assert(obj.typ != nil)
	}
	}
	break
	}
	}

	check.arityMatch(s, nil)

	// declare all variables
	// (only at this point are the variable scopes (parents) set)
	for i, name := range s.Names {
	check.declare(check.scope, name, lhs0[i])
	}

	default:
	check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
	}

	case *ast.TypeSpec:
	obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
	check.declare(check.scope, s.Name, obj)
	check.typeDecl(obj, s.Type, nil, nil)

	default:
	check.invalidAST(s.Pos(), "const, type, or var declaration expected")
	}
	}

	default:
	check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
	}
	}