[dev.typeparams] cmd/compile/internal/types2: delay interface check for type bounds

While at it, clean up code for collecting/declaring type parameters.

For #40789.

Change-Id: I0855137d5ee85c0ae2fa60d33b28c24a33132fbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/331690
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2021-06-29 12:22:21 -07:00
parent 1cd505c353
commit 9cb1b0f50b
4 changed files with 82 additions and 65 deletions

View file

@ -674,77 +674,54 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
} }
func (check *Checker) collectTypeParams(list []*syntax.Field) (tparams []*TypeName) { func (check *Checker) collectTypeParams(list []*syntax.Field) []*TypeName {
// Type parameter lists should not be empty. The parser will tparams := make([]*TypeName, len(list))
// complain but we still may get an incorrect AST: ignore it.
if len(list) == 0 {
return
}
// Declare type parameters up-front, with empty interface as type bound. // Declare type parameters up-front.
// The scope of type parameters starts at the beginning of the type parameter // The scope of type parameters starts at the beginning of the type parameter
// list (so we can have mutually recursive parameterized interfaces). // list (so we can have mutually recursive parameterized type bounds).
for _, f := range list { for i, f := range list {
tparams = check.declareTypeParam(tparams, f.Name) tparams[i] = check.declareTypeParam(i, f.Name)
} }
var bound Type var bound Type
for i, j := 0, 0; i < len(list); i = j { for i, f := range list {
f := list[i] // Optimization: Re-use the previous type bound if it hasn't changed.
// This also preserves the grouped output of type parameter lists
// determine the range of type parameters list[i:j] with identical type bound // when printing type strings.
// (declared as in (type a, b, c B)) if i == 0 || f.Type != list[i-1].Type {
j = i + 1 bound = check.boundType(f.Type)
for j < len(list) && list[j].Type == f.Type {
j++
} }
tparams[i].typ.(*TypeParam).bound = bound
// this should never be the case, but be careful
if f.Type == nil {
continue
}
// The predeclared identifier "any" is visible only as a constraint
// in a type parameter list. Look for it before general constraint
// resolution.
if tident, _ := unparen(f.Type).(*syntax.Name); tident != nil && tident.Value == "any" && check.lookup("any") == nil {
bound = universeAny
} else {
bound = check.typ(f.Type)
}
// type bound must be an interface
// TODO(gri) We should delay the interface check because
// we may not have a complete interface yet:
// type C(type T C) interface {}
// (issue #39724).
if _, ok := under(bound).(*Interface); ok {
// set the type bounds
for i < j {
tparams[i].typ.(*TypeParam).bound = bound
i++
}
} else if bound != Typ[Invalid] {
check.errorf(f.Type, "%s is not an interface", bound)
}
}
return
}
func (check *Checker) declareTypeParam(tparams []*TypeName, name *syntax.Name) []*TypeName {
tpar := NewTypeName(name.Pos(), check.pkg, name.Value, nil)
check.NewTypeParam(tpar, len(tparams), &emptyInterface) // assigns type to tpar as a side-effect
check.declare(check.scope, name, tpar, check.scope.pos) // TODO(gri) check scope position
tparams = append(tparams, tpar)
if check.conf.Trace {
check.trace(name.Pos(), "type param = %v", tparams[len(tparams)-1])
} }
return tparams return tparams
} }
func (check *Checker) declareTypeParam(index int, name *syntax.Name) *TypeName {
tpar := NewTypeName(name.Pos(), check.pkg, name.Value, nil)
check.NewTypeParam(tpar, index, nil) // assigns type to tpar as a side-effect
check.declare(check.scope, name, tpar, check.scope.pos) // TODO(gri) check scope position
return tpar
}
// boundType type-checks the type expression e and returns its type, or Typ[Invalid].
// The type must be an interface, including the predeclared type "any".
func (check *Checker) boundType(e syntax.Expr) Type {
// The predeclared identifier "any" is visible only as a type bound in a type parameter list.
if name, _ := unparen(e).(*syntax.Name); name != nil && name.Value == "any" && check.lookup("any") == nil {
return universeAny
}
bound := check.typ(e)
check.later(func() {
if _, ok := under(bound).(*Interface); !ok && bound != Typ[Invalid] {
check.errorf(e, "%s is not an interface", bound)
}
})
return bound
}
func (check *Checker) collectMethods(obj *TypeName) { func (check *Checker) collectMethods(obj *TypeName) {
// get associated methods // get associated methods
// (Checker.collectObjects only collects methods with non-blank names; // (Checker.collectObjects only collects methods with non-blank names;

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@ -48,10 +48,9 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
// blank identifiers were found => use rewritten receiver type // blank identifiers were found => use rewritten receiver type
recvTyp = isubst(recvPar.Type, smap) recvTyp = isubst(recvPar.Type, smap)
} }
// TODO(gri) rework declareTypeParams sig.rparams = make([]*TypeName, len(rparams))
sig.rparams = nil for i, rparam := range rparams {
for _, rparam := range rparams { sig.rparams[i] = check.declareTypeParam(i, rparam)
sig.rparams = check.declareTypeParam(sig.rparams, rparam)
} }
// determine receiver type to get its type parameters // determine receiver type to get its type parameters
// and the respective type parameter bounds // and the respective type parameter bounds

View file

@ -0,0 +1,37 @@
// 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.
package main
import "fmt"
func main() {
m := map[string]int{
"a": 6,
"b": 7,
}
fmt.Println(copyMap[map[string]int, string, int](m))
}
type Map[K comparable, V any] interface {
map[K] V
}
func copyMap[M Map[K, V], K comparable, V any](m M) M {
m1 := make(M)
for k, v := range m {
m1[k] = v
}
return m1
}
// simpler test case from the same issue
type A[X comparable] interface {
[]X
}
func f[B A[X], X comparable]() B {
return nil
}

View file

@ -626,7 +626,11 @@ func (t *TypeParam) SetId(id uint64) {
} }
func (t *TypeParam) Bound() *Interface { func (t *TypeParam) Bound() *Interface {
iface := asInterface(t.bound) // we may not have an interface (error reported elsewhere)
iface, _ := under(t.bound).(*Interface)
if iface == nil {
return &emptyInterface
}
// use the type bound position if we have one // use the type bound position if we have one
pos := nopos pos := nopos
if n, _ := t.bound.(*Named); n != nil { if n, _ := t.bound.(*Named); n != nil {