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https://github.com/golang/go
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[dev.typeparams] go/types: move instantiation code to instantiate.go (cleanup)
This is a port of CL 333589 to go/types. Change-Id: Ib9fb1b09e10c400e62d20b55ff0558f3a92fc0eb Reviewed-on: https://go-review.googlesource.com/c/go/+/335072 Trust: Robert Findley <rfindley@google.com> Run-TryBot: Robert Findley <rfindley@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Rob Findley
Robert Findley
parent
41ff0aac13
commit
4a72be87b3
@ -2,6 +2,9 @@
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file implements instantiation of generic types
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// through substitution of type parameters by type arguments.
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package types
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import (
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@ -9,6 +12,106 @@ import (
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"go/token"
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)
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// Instantiate instantiates the type typ with the given type arguments
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// targs. To check type constraint satisfaction, verify must be set.
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// pos and posList correspond to the instantiation and type argument
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// positions respectively; posList may be nil or shorter than the number
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// of type arguments provided.
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// typ must be a *Named or a *Signature type, and its number of type
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// parameters must match the number of provided type arguments.
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// The receiver (check) may be nil if and only if verify is not set.
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// The result is a new, instantiated (not generic) type of the same kind
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// (either a *Named or a *Signature).
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// Any methods attached to a *Named are simply copied; they are not
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// instantiated.
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func (check *Checker) Instantiate(pos token.Pos, typ Type, targs []Type, posList []token.Pos, verify bool) (res Type) {
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if verify && check == nil {
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panic("cannot have nil receiver if verify is set")
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}
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if check != nil && trace {
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check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
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check.indent++
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defer func() {
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check.indent--
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var under Type
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if res != nil {
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// Calling under() here may lead to endless instantiations.
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// Test case: type T[P any] T[P]
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// TODO(gri) investigate if that's a bug or to be expected.
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under = res.Underlying()
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}
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check.trace(pos, "=> %s (under = %s)", res, under)
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}()
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}
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assert(len(posList) <= len(targs))
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// TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
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var tparams []*TypeName
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switch t := typ.(type) {
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case *Named:
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tparams = t.TParams()
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case *Signature:
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tparams = t.tparams
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defer func() {
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// If we had an unexpected failure somewhere don't panic below when
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// asserting res.(*Signature). Check for *Signature in case Typ[Invalid]
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// is returned.
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if _, ok := res.(*Signature); !ok {
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return
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}
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// If the signature doesn't use its type parameters, subst
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// will not make a copy. In that case, make a copy now (so
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// we can set tparams to nil w/o causing side-effects).
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if t == res {
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copy := *t
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res = ©
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}
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// After instantiating a generic signature, it is not generic
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// anymore; we need to set tparams to nil.
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res.(*Signature).tparams = nil
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}()
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default:
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// only types and functions can be generic
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panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
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}
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// the number of supplied types must match the number of type parameters
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if len(targs) != len(tparams) {
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// TODO(gri) provide better error message
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if check != nil {
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check.errorf(atPos(pos), _Todo, "got %d arguments but %d type parameters", len(targs), len(tparams))
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return Typ[Invalid]
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}
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panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
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}
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if len(tparams) == 0 {
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return typ // nothing to do (minor optimization)
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}
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smap := makeSubstMap(tparams, targs)
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// check bounds
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if verify {
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for i, tname := range tparams {
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// best position for error reporting
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pos := pos
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if i < len(posList) {
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pos = posList[i]
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}
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// stop checking bounds after the first failure
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if !check.satisfies(pos, targs[i], tname.typ.(*TypeParam), smap) {
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break
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}
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}
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}
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return check.subst(pos, typ, smap)
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}
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// InstantiateLazy is like Instantiate, but avoids actually
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// instantiating the type until needed.
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func (check *Checker) InstantiateLazy(pos token.Pos, typ Type, targs []Type, verify bool) (res Type) {
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@ -25,3 +128,85 @@ func (check *Checker) InstantiateLazy(pos token.Pos, typ Type, targs []Type, ver
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verify: verify,
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}
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}
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// satisfies reports whether the type argument targ satisfies the constraint of type parameter
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// parameter tpar (after any of its type parameters have been substituted through smap).
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// A suitable error is reported if the result is false.
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// TODO(gri) This should be a method of interfaces or type sets.
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func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
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iface := tpar.Bound()
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if iface.Empty() {
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return true // no type bound
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}
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// The type parameter bound is parameterized with the same type parameters
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// as the instantiated type; before we can use it for bounds checking we
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// need to instantiate it with the type arguments with which we instantiate
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// the parameterized type.
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iface = check.subst(pos, iface, smap).(*Interface)
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// targ must implement iface (methods)
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// - check only if we have methods
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if iface.NumMethods() > 0 {
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// If the type argument is a pointer to a type parameter, the type argument's
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// method set is empty.
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// TODO(gri) is this what we want? (spec question)
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if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
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check.errorf(atPos(pos), 0, "%s has no methods", targ)
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return false
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}
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if m, wrong := check.missingMethod(targ, iface, true); m != nil {
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// TODO(gri) needs to print updated name to avoid major confusion in error message!
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// (print warning for now)
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// Old warning:
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// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
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if m.name == "==" {
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// We don't want to report "missing method ==".
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check.softErrorf(atPos(pos), 0, "%s does not satisfy comparable", targ)
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} else if wrong != nil {
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// TODO(gri) This can still report uninstantiated types which makes the error message
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// more difficult to read then necessary.
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// TODO(rFindley) should this use parentheses rather than ':' for qualification?
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check.softErrorf(atPos(pos), _Todo,
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"%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
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targ, tpar.bound, wrong, m,
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)
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} else {
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check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
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}
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return false
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}
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}
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// targ's underlying type must also be one of the interface types listed, if any
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if iface.typeSet().types == nil {
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return true // nothing to do
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}
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// If targ is itself a type parameter, each of its possible types, but at least one, must be in the
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// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
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if targ := asTypeParam(targ); targ != nil {
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targBound := targ.Bound()
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if targBound.typeSet().types == nil {
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check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
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return false
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}
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return iface.is(func(typ Type, tilde bool) bool {
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// TODO(gri) incorporate tilde information!
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if !iface.isSatisfiedBy(typ) {
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// TODO(gri) match this error message with the one below (or vice versa)
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check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, typ, iface.typeSet().types)
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return false
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}
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return true
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})
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}
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// Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
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if !iface.isSatisfiedBy(targ) {
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check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types)
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return false
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}
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return true
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}
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@ -2,9 +2,7 @@
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file implements instantiation of generic types
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// through substitution of type parameters by actual
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// types.
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// This file implements type parameter substitution.
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package types
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@ -56,188 +54,6 @@ func (m *substMap) lookup(tpar *TypeParam) Type {
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return tpar
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}
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// Instantiate instantiates the type typ with the given type arguments
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// targs. To check type constraint satisfaction, verify must be set.
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// pos and posList correspond to the instantiation and type argument
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// positions respectively; posList may be nil or shorter than the number
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// of type arguments provided.
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// typ must be a *Named or a *Signature type, and its number of type
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// parameters must match the number of provided type arguments.
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// The receiver (check) may be nil if and only if verify is not set.
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// The result is a new, instantiated (not generic) type of the same kind
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// (either a *Named or a *Signature).
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// Any methods attached to a *Named are simply copied; they are not
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// instantiated.
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func (check *Checker) Instantiate(pos token.Pos, typ Type, targs []Type, posList []token.Pos, verify bool) (res Type) {
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if verify && check == nil {
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panic("cannot have nil receiver if verify is set")
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}
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if check != nil && trace {
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check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
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check.indent++
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defer func() {
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check.indent--
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var under Type
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if res != nil {
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// Calling under() here may lead to endless instantiations.
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// Test case: type T[P any] T[P]
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// TODO(gri) investigate if that's a bug or to be expected.
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under = res.Underlying()
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}
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check.trace(pos, "=> %s (under = %s)", res, under)
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}()
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}
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assert(len(posList) <= len(targs))
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// TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
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var tparams []*TypeName
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switch t := typ.(type) {
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case *Named:
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tparams = t.TParams()
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case *Signature:
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tparams = t.tparams
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defer func() {
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// If we had an unexpected failure somewhere don't panic below when
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// asserting res.(*Signature). Check for *Signature in case Typ[Invalid]
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// is returned.
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if _, ok := res.(*Signature); !ok {
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return
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}
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// If the signature doesn't use its type parameters, subst
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// will not make a copy. In that case, make a copy now (so
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// we can set tparams to nil w/o causing side-effects).
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if t == res {
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copy := *t
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res = ©
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}
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// After instantiating a generic signature, it is not generic
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// anymore; we need to set tparams to nil.
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res.(*Signature).tparams = nil
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}()
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default:
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// only types and functions can be generic
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panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
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}
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// the number of supplied types must match the number of type parameters
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if len(targs) != len(tparams) {
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// TODO(gri) provide better error message
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if check != nil {
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check.errorf(atPos(pos), _Todo, "got %d arguments but %d type parameters", len(targs), len(tparams))
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return Typ[Invalid]
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}
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panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
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}
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if len(tparams) == 0 {
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return typ // nothing to do (minor optimization)
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}
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smap := makeSubstMap(tparams, targs)
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// check bounds
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if verify {
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for i, tname := range tparams {
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// best position for error reporting
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pos := pos
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if i < len(posList) {
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pos = posList[i]
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}
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// stop checking bounds after the first failure
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if !check.satisfies(pos, targs[i], tname.typ.(*TypeParam), smap) {
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break
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}
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}
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}
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return check.subst(pos, typ, smap)
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}
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// satisfies reports whether the type argument targ satisfies the constraint of type parameter
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// parameter tpar (after any of its type parameters have been substituted through smap).
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// A suitable error is reported if the result is false.
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// TODO(gri) This should be a method of interfaces or type sets.
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func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap *substMap) bool {
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iface := tpar.Bound()
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if iface.Empty() {
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return true // no type bound
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}
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// The type parameter bound is parameterized with the same type parameters
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// as the instantiated type; before we can use it for bounds checking we
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// need to instantiate it with the type arguments with which we instantiate
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// the parameterized type.
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iface = check.subst(pos, iface, smap).(*Interface)
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// targ must implement iface (methods)
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// - check only if we have methods
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if iface.NumMethods() > 0 {
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// If the type argument is a pointer to a type parameter, the type argument's
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// method set is empty.
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// TODO(gri) is this what we want? (spec question)
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if base, isPtr := deref(targ); isPtr && asTypeParam(base) != nil {
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check.errorf(atPos(pos), 0, "%s has no methods", targ)
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return false
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}
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if m, wrong := check.missingMethod(targ, iface, true); m != nil {
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// TODO(gri) needs to print updated name to avoid major confusion in error message!
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// (print warning for now)
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// Old warning:
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// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)
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if m.name == "==" {
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// We don't want to report "missing method ==".
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check.softErrorf(atPos(pos), 0, "%s does not satisfy comparable", targ)
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} else if wrong != nil {
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// TODO(gri) This can still report uninstantiated types which makes the error message
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// more difficult to read then necessary.
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// TODO(rFindley) should this use parentheses rather than ':' for qualification?
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check.softErrorf(atPos(pos), _Todo,
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"%s does not satisfy %s: wrong method signature\n\tgot %s\n\twant %s",
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targ, tpar.bound, wrong, m,
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)
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} else {
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check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (missing method %s)", targ, tpar.bound, m.name)
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}
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return false
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}
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}
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// targ's underlying type must also be one of the interface types listed, if any
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if iface.typeSet().types == nil {
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return true // nothing to do
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}
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// If targ is itself a type parameter, each of its possible types, but at least one, must be in the
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// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
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if targ := asTypeParam(targ); targ != nil {
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targBound := targ.Bound()
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if targBound.typeSet().types == nil {
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check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
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return false
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}
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return iface.is(func(typ Type, tilde bool) bool {
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// TODO(gri) incorporate tilde information!
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if !iface.isSatisfiedBy(typ) {
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// TODO(gri) match this error message with the one below (or vice versa)
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check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, typ, iface.typeSet().types)
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return false
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}
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return true
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})
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}
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// Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
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if !iface.isSatisfiedBy(targ) {
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check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types)
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return false
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}
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return true
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}
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// subst returns the type typ with its type parameters tpars replaced by
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// the corresponding type arguments targs, recursively.
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// subst is functional in the sense that it doesn't modify the incoming
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