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go/types: clean up panics in instantiation

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This is a straightforward port of CL 341862 to go/types.

Change-Id: I4214c08d2889e2daf40254385656c6beed79571d
Reviewed-on: https://go-review.googlesource.com/c/go/+/342487
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley 2021-08-16 15:59:08 -04:00
parent bacbc33439
commit 4d00fcbc43
2 changed files with 28 additions and 22 deletions
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35
src/go/types/instantiate.go
View file

@ -53,15 +53,18 @@ func (check *Checker) Instantiate(pos token.Pos, typ Type, targs []Type, posList
// only types and functions can be generic // only types and functions can be generic
panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ)) panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
} }
inst := check.instantiate(pos, typ, tparams, targs, nil)
inst := check.instantiate(pos, typ, tparams, targs, posList, nil) if verify {
if verify && len(tparams) == len(targs) { assert(len(posList) <= len(targs))
if len(tparams) == len(targs) {
check.verify(pos, tparams, targs, posList) check.verify(pos, tparams, targs, posList)
} }
}
return inst return inst
} }
func (check *Checker) instantiate(pos token.Pos, typ Type, tparams []*TypeName, targs []Type, posList []token.Pos, typMap map[string]*Named) (res Type) { func (check *Checker) instantiate(pos token.Pos, typ Type, tparams []*TypeName, targs []Type, typMap map[string]*Named) (res Type) {
// the number of supplied types must match the number of type parameters // the number of supplied types must match the number of type parameters
if len(targs) != len(tparams) { if len(targs) != len(tparams) {
// TODO(gri) provide better error message // TODO(gri) provide better error message
@ -88,8 +91,6 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, tparams []*TypeName,
}() }()
} }
assert(len(posList) <= len(targs))
// TODO(gri) What is better here: work with TypeParams, or work with TypeNames? // TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
if len(tparams) == 0 { if len(tparams) == 0 {
@ -101,14 +102,21 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, tparams []*TypeName,
// instantiateLazy avoids actually instantiating the type until needed. typ // instantiateLazy avoids actually instantiating the type until needed. typ
// must be a *Named type. // must be a *Named type.
func (check *Checker) instantiateLazy(pos token.Pos, base *Named, targs []Type, posList []token.Pos, verify bool) Type { func (check *Checker) instantiateLazy(pos token.Pos, orig *Named, targs []Type, posList []token.Pos, verify bool) Type {
if verify && base.TParams().Len() == len(targs) { if verify {
// TODO: lift the nil check in verify to here. if check == nil {
// Provide a more useful panic instead of panicking at check.later below.
panic("cannot have nil Checker if verifying constraints")
}
assert(len(posList) <= len(targs))
if orig.TParams().Len() == len(targs) {
check.later(func() { check.later(func() {
check.verify(pos, base.tparams.list(), targs, posList) check.verify(pos, orig.tparams.list(), targs, posList)
}) })
} }
h := instantiatedHash(base, targs) }
h := instantiatedHash(orig, targs)
if check != nil { if check != nil {
// typ may already have been instantiated with identical type arguments. In // typ may already have been instantiated with identical type arguments. In
// that case, re-use the existing instance. // that case, re-use the existing instance.
@ -117,10 +125,10 @@ func (check *Checker) instantiateLazy(pos token.Pos, base *Named, targs []Type,
} }
} }
tname := NewTypeName(pos, base.obj.pkg, base.obj.name, nil) tname := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
named := check.newNamed(tname, base, nil, nil, nil) // methods and tparams are set when named is loaded. named := check.newNamed(tname, orig, nil, nil, nil) // methods and tparams are set when named is loaded
named.targs = targs named.targs = targs
named.instance = &instance{pos, posList} named.instance = &instance{pos}
if check != nil { if check != nil {
check.typMap[h] = named check.typMap[h] = named
@ -133,7 +141,6 @@ func (check *Checker) verify(pos token.Pos, tparams []*TypeName, targs []Type, p
if check == nil { if check == nil {
panic("cannot have nil Checker if verifying constraints") panic("cannot have nil Checker if verifying constraints")
} }
smap := makeSubstMap(tparams, targs) smap := makeSubstMap(tparams, targs)
for i, tname := range tparams { for i, tname := range tparams {
// best position for error reporting // best position for error reporting

7
src/go/types/named.go
View file

@ -248,11 +248,10 @@ func (n *Named) setUnderlying(typ Type) {
// instance holds position information for use in lazy instantiation. // instance holds position information for use in lazy instantiation.
// //
// TODO(rfindley): come up with a better name for this type, now that its usage // TODO(rfindley): instance is probably unnecessary now. See if it can be
// has changed. // eliminated.
type instance struct { type instance struct {
pos token.Pos // position of type instantiation; for error reporting only pos token.Pos // position of type instantiation; for error reporting only
posList []token.Pos // position of each targ; for error reporting only
} }
// expand ensures that the underlying type of n is instantiated. // expand ensures that the underlying type of n is instantiated.
@ -276,7 +275,7 @@ func (n *Named) expand(typMap map[string]*Named) *Named {
} }
} }
inst := n.check.instantiate(n.instance.pos, n.orig.underlying, n.TParams().list(), n.targs, n.instance.posList, typMap) inst := n.check.instantiate(n.instance.pos, n.orig.underlying, n.TParams().list(), n.targs, typMap)
n.underlying = inst n.underlying = inst
n.fromRHS = inst n.fromRHS = inst
n.instance = nil n.instance = nil