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// Copyright 2018 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.
// Indexed package export.
//
// The indexed export data format is an evolution of the previous
// binary export data format. Its chief contribution is introducing an
// index table, which allows efficient random access of individual
// declarations and inline function bodies. In turn, this allows
// avoiding unnecessary work for compilation units that import large
// packages.
//
//
// The top-level data format is structured as:
//
// Header struct {
// Tag byte // 'i'
// Version uvarint
// StringSize uvarint
// DataSize uvarint
// }
//
// Strings [StringSize]byte
// Data [DataSize]byte
//
// MainIndex []struct{
// PkgPath stringOff
// PkgName stringOff
// PkgHeight uvarint
//
// Decls []struct{
// Name stringOff
// Offset declOff
// }
// }
//
// Fingerprint [8]byte
//
// uvarint means a uint64 written out using uvarint encoding.
//
// []T means a uvarint followed by that many T objects. In other
// words:
//
// Len uvarint
// Elems [Len]T
//
// stringOff means a uvarint that indicates an offset within the
// Strings section. At that offset is another uvarint, followed by
// that many bytes, which form the string value.
//
// declOff means a uvarint that indicates an offset within the Data
// section where the associated declaration can be found.
//
//
// There are five kinds of declarations, distinguished by their first
// byte:
//
// type Var struct {
// Tag byte // 'V'
// Pos Pos
// Type typeOff
// }
//
// type Func struct {
// Tag byte // 'F' or 'G'
// Pos Pos
// TypeParams []typeOff // only present if Tag == 'G'
// Signature Signature
// }
//
// type Const struct {
// Tag byte // 'C'
// Pos Pos
// Value Value
// }
//
// type Type struct {
// Tag byte // 'T' or 'U'
// Pos Pos
// TypeParams []typeOff // only present if Tag == 'U'
// Underlying typeOff
//
// Methods []struct{ // omitted if Underlying is an interface type
// Pos Pos
// Name stringOff
// Recv Param
// Signature Signature
// }
// }
//
// type Alias struct {
// Tag byte // 'A'
// Pos Pos
// Type typeOff
// }
//
// // "Automatic" declaration of each typeparam
// type TypeParam struct {
// Tag byte // 'P'
// Pos Pos
// Implicit bool
// Constraint typeOff
// }
//
// typeOff means a uvarint that either indicates a predeclared type,
// or an offset into the Data section. If the uvarint is less than
// predeclReserved, then it indicates the index into the predeclared
// types list (see predeclared in bexport.go for order). Otherwise,
// subtracting predeclReserved yields the offset of a type descriptor.
//
// Value means a type, kind, and type-specific value. See
// (*exportWriter).value for details.
//
//
// There are twelve kinds of type descriptors, distinguished by an itag:
//
// type DefinedType struct {
// Tag itag // definedType
// Name stringOff
// PkgPath stringOff
// }
//
// type PointerType struct {
// Tag itag // pointerType
// Elem typeOff
// }
//
// type SliceType struct {
// Tag itag // sliceType
// Elem typeOff
// }
//
// type ArrayType struct {
// Tag itag // arrayType
// Len uint64
// Elem typeOff
// }
//
// type ChanType struct {
// Tag itag // chanType
// Dir uint64 // 1 RecvOnly; 2 SendOnly; 3 SendRecv
// Elem typeOff
// }
//
// type MapType struct {
// Tag itag // mapType
// Key typeOff
// Elem typeOff
// }
//
// type FuncType struct {
// Tag itag // signatureType
// PkgPath stringOff
// Signature Signature
// }
//
// type StructType struct {
// Tag itag // structType
// PkgPath stringOff
// Fields []struct {
// Pos Pos
// Name stringOff
// Type typeOff
// Embedded bool
// Note stringOff
// }
// }
//
// type InterfaceType struct {
// Tag itag // interfaceType
// PkgPath stringOff
// Embeddeds []struct {
// Pos Pos
// Type typeOff
// }
// Methods []struct {
// Pos Pos
// Name stringOff
// Signature Signature
// }
// }
//
// // Reference to a type param declaration
// type TypeParamType struct {
// Tag itag // typeParamType
// Name stringOff
// PkgPath stringOff
// }
//
// // Instantiation of a generic type (like List[T2] or List[int])
// type InstanceType struct {
// Tag itag // instanceType
// Pos pos
// TypeArgs []typeOff
// BaseType typeOff
// }
//
// type UnionType struct {
// Tag itag // interfaceType
// Terms []struct {
// tilde bool
// Type typeOff
// }
// }
//
//
//
// type Signature struct {
// Params []Param
// Results []Param
// Variadic bool // omitted if Results is empty
// }
//
// type Param struct {
// Pos Pos
// Name stringOff
// Type typOff
// }
//
//
// Pos encodes a file:line:column triple, incorporating a simple delta
// encoding scheme within a data object. See exportWriter.pos for
// details.
//
//
// Compiler-specific details.
//
// cmd/compile writes out a second index for inline bodies and also
// appends additional compiler-specific details after declarations.
// Third-party tools are not expected to depend on these details and
// they're expected to change much more rapidly, so they're omitted
// here. See exportWriter's varExt/funcExt/etc methods for details.
package typecheck
import (
"go/constant"
"strconv"
"strings"
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/types"
)
// predeclReserved is the number of type offsets reserved for types
// implicitly declared in the universe block.
const predeclReserved = 32
// An itag distinguishes the kind of type that was written into the
// indexed export format.
type itag uint64
const (
// Types
definedType itag = iota
pointerType
sliceType
arrayType
chanType
mapType
signatureType
structType
interfaceType
typeParamType
instanceType // Instantiation of a generic type
unionType
)
const (
debug = false
magic = 0x6742937dc293105
)
// exportPath returns the path for pkg as it appears in the iexport
// file format. For historical reasons (before cmd/compile required
// the -p flag), the local package is represented as the empty string,
// instead of its actual path.
func exportPath(pkg *types.Pkg) string {
if pkg == types.LocalPkg {
return ""
}
return pkg.Path
}
const blankMarker = "$"
// TparamExportName creates a unique name for type param in a method or a generic
// type, using the specified unique prefix and the index of the type param. The index
// is only used if the type param is blank, in which case the blank is replace by
// "$<index>". A unique name is needed for later substitution in the compiler and
// export/import that keeps blank type params associated with the correct constraint.
func TparamExportName(prefix string, name string, index int) string {
if name == "_" {
name = blankMarker + strconv.Itoa(index)
}
return prefix + "." + name
}
// TparamName returns the real name of a type parameter, after stripping its
// qualifying prefix and reverting blank-name encoding. See TparamExportName
// for details.
func TparamName(exportName string) string {
// Remove the "path" from the type param name that makes it unique.
ix := strings.LastIndex(exportName, ".")
if ix < 0 {
return ""
}
name := exportName[ix+1:]
if strings.HasPrefix(name, blankMarker) {
return "_"
}
return name
}
func constTypeOf(typ *types.Type) constant.Kind {
switch typ {
case types.UntypedInt, types.UntypedRune:
return constant.Int
case types.UntypedFloat:
return constant.Float
case types.UntypedComplex:
return constant.Complex
}
switch typ.Kind() {
case types.TBOOL:
return constant.Bool
case types.TSTRING:
return constant.String
case types.TINT, types.TINT8, types.TINT16, types.TINT32, types.TINT64,
types.TUINT, types.TUINT8, types.TUINT16, types.TUINT32, types.TUINT64, types.TUINTPTR:
return constant.Int
case types.TFLOAT32, types.TFLOAT64:
return constant.Float
case types.TCOMPLEX64, types.TCOMPLEX128:
return constant.Complex
}
base.Fatalf("unexpected constant type: %v", typ)
return 0
}
func intSize(typ *types.Type) (signed bool, maxBytes uint) {
if typ.IsUntyped() {
return true, ir.ConstPrec / 8
}
switch typ.Kind() {
case types.TFLOAT32, types.TCOMPLEX64:
return true, 3
case types.TFLOAT64, types.TCOMPLEX128:
return true, 7
}
signed = typ.IsSigned()
maxBytes = uint(typ.Size())
// The go/types API doesn't expose sizes to importers, so they
// don't know how big these types are.
switch typ.Kind() {
case types.TINT, types.TUINT, types.TUINTPTR:
maxBytes = 8
}
return
}
func isNonEmptyAssign(n ir.Node) bool {
switch n.Op() {
case ir.OAS:
if n.(*ir.AssignStmt).Y != nil {
return true
}
case ir.OAS2, ir.OAS2DOTTYPE, ir.OAS2FUNC, ir.OAS2MAPR, ir.OAS2RECV:
return true
}
return false
}
func isNamedTypeSwitch(x ir.Node) bool {
guard, ok := x.(*ir.TypeSwitchGuard)
return ok && guard.Tag != nil
}
func simplifyForExport(n ir.Node) ir.Node {
switch n.Op() {
case ir.OPAREN:
n := n.(*ir.ParenExpr)
return simplifyForExport(n.X)
}
return n
}
// The name used for dictionary parameters or local variables.
const LocalDictName = ".dict"