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// Copyright 2021 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.
//go:build !go1.18
// +build !go1.18
package typeparams
import (
"go/ast"
"go/token"
"go/types"
)
func unsupported() {
panic("type parameters are unsupported at this go version")
}
// IndexListExpr is a placeholder type, as type parameters are not supported at
// this Go version. Its methods panic on use.
type IndexListExpr struct {
ast.Expr
X ast.Expr // expression
Lbrack token.Pos // position of "["
Indices []ast.Expr // index expressions
Rbrack token.Pos // position of "]"
}
// ForTypeSpec returns an empty field list, as type parameters on not supported
// at this Go version.
func ForTypeSpec(*ast.TypeSpec) *ast.FieldList {
return nil
}
// ForFuncType returns an empty field list, as type parameters are not
// supported at this Go version.
func ForFuncType(*ast.FuncType) *ast.FieldList {
return nil
}
// TypeParam is a placeholder type, as type parameters are not supported at
// this Go version. Its methods panic on use.
type TypeParam struct{ types.Type }
func (*TypeParam) Index() int { unsupported(); return 0 }
func (*TypeParam) Constraint() types.Type { unsupported(); return nil }
func (*TypeParam) Obj() *types.TypeName { unsupported(); return nil }
// TypeParamList is a placeholder for an empty type parameter list.
type TypeParamList struct{}
func (*TypeParamList) Len() int { return 0 }
func (*TypeParamList) At(int) *TypeParam { unsupported(); return nil }
// TypeList is a placeholder for an empty type list.
type TypeList struct{}
func (*TypeList) Len() int { return 0 }
func (*TypeList) At(int) types.Type { unsupported(); return nil }
// NewTypeParam is unsupported at this Go version, and panics.
func NewTypeParam(name *types.TypeName, constraint types.Type) *TypeParam {
unsupported()
return nil
}
// SetTypeParamConstraint is unsupported at this Go version, and panics.
func SetTypeParamConstraint(tparam *TypeParam, constraint types.Type) {
unsupported()
}
// NewSignatureType calls types.NewSignature, panicking if recvTypeParams or
// typeParams is non-empty.
func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
if len(recvTypeParams) != 0 || len(typeParams) != 0 {
panic("signatures cannot have type parameters at this Go version")
}
return types.NewSignature(recv, params, results, variadic)
}
// ForSignature returns an empty slice.
func ForSignature(*types.Signature) *TypeParamList {
return nil
}
// RecvTypeParams returns a nil slice.
func RecvTypeParams(sig *types.Signature) *TypeParamList {
return nil
}
// IsComparable returns false, as no interfaces are type-restricted at this Go
// version.
func IsComparable(*types.Interface) bool {
return false
}
// IsMethodSet returns true, as no interfaces are type-restricted at this Go
// version.
func IsMethodSet(*types.Interface) bool {
return true
}
// IsImplicit returns false, as no interfaces are implicit at this Go version.
func IsImplicit(*types.Interface) bool {
return false
}
// MarkImplicit does nothing, because this Go version does not have implicit
// interfaces.
func MarkImplicit(*types.Interface) {}
// ForNamed returns an empty type parameter list, as type parameters are not
// supported at this Go version.
func ForNamed(*types.Named) *TypeParamList {
return nil
}
// SetForNamed panics if tparams is non-empty.
func SetForNamed(_ *types.Named, tparams []*TypeParam) {
if len(tparams) > 0 {
unsupported()
}
}
// NamedTypeArgs returns nil.
func NamedTypeArgs(*types.Named) *TypeList {
return nil
}
// NamedTypeOrigin is the identity method at this Go version.
func NamedTypeOrigin(named *types.Named) types.Type {
return named
}
// Term holds information about a structural type restriction.
type Term struct {
tilde bool
typ types.Type
}
func (m *Term) Tilde() bool { return m.tilde }
func (m *Term) Type() types.Type { return m.typ }
func (m *Term) String() string {
pre := ""
if m.tilde {
pre = "~"
}
return pre + m.typ.String()
}
// NewTerm is unsupported at this Go version, and panics.
func NewTerm(tilde bool, typ types.Type) *Term {
return &Term{tilde, typ}
}
// Union is a placeholder type, as type parameters are not supported at this Go
// version. Its methods panic on use.
type Union struct{ types.Type }
func (*Union) Len() int { return 0 }
func (*Union) Term(i int) *Term { unsupported(); return nil }
// NewUnion is unsupported at this Go version, and panics.
func NewUnion(terms []*Term) *Union {
unsupported()
return nil
}
// InitInstanceInfo is a noop at this Go version.
func InitInstanceInfo(*types.Info) {}
// Instance is a placeholder type, as type parameters are not supported at this
// Go version.
type Instance struct {
TypeArgs *TypeList
Type types.Type
}
// GetInstances returns a nil map, as type parameters are not supported at this
// Go version.
func GetInstances(info *types.Info) map[*ast.Ident]Instance { return nil }
// Context is a placeholder type, as type parameters are not supported at
// this Go version.
type Context struct{}
// Instantiate is unsupported on this Go version, and panics.
func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
unsupported()
return nil, nil
}
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