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go/types: minor cleanup of instantiation

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This CL addresses a couple TODOs related to instantiation:
 - factor out resolving the best environment
 - don't eagerly resolve substituted instances

Change-Id: I4a5de7ea7939b6f272991071f591d622dec04b53
Reviewed-on: https://go-review.googlesource.com/c/go/+/349429
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:
Robert Findley 2021-09-11 23:06:41 -04:00
parent a0f3129466
commit cb4e1de021
2 changed files with 29 additions and 40 deletions
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38
src/go/types/named.go
View File

@ -219,6 +219,21 @@ func (n *Named) setUnderlying(typ Type) {
}
}
// bestEnv returns the best available environment. In order of preference:
// - the given env, if non-nil
// - the Checker env, if check is non-nil
// - a new environment
func (check *Checker) bestEnv(env *Environment) *Environment {
if env != nil {
return env
}
if check != nil {
assert(check.conf.Environment != nil)
return check.conf.Environment
}
return NewEnvironment()
}
// expandNamed ensures that the underlying type of n is instantiated.
// The underlying type will be Typ[Invalid] if there was an error.
func expandNamed(env *Environment, n *Named, instPos token.Pos) (tparams *TypeParamList, underlying Type, methods []*Func) {
@ -227,24 +242,15 @@ func expandNamed(env *Environment, n *Named, instPos token.Pos) (tparams *TypePa
check := n.check
if check.validateTArgLen(instPos, n.orig.tparams.Len(), n.targs.Len()) {
// TODO(rfindley): handling an optional Checker and Environment here (and
// in subst) feels overly complicated. Can we simplify?
if env == nil {
if check != nil {
env = check.conf.Environment
} else {
// If we're instantiating lazily, we might be outside the scope of a
// type-checking pass. In that case we won't have a pre-existing
// environment, but don't want to create a duplicate of the current
// instance in the process of expansion.
env = NewEnvironment()
}
h := env.typeHash(n.orig, n.targs.list())
// ensure that an instance is recorded for h to avoid infinite recursion.
env.typeForHash(h, n)
}
// We must always have an env, to avoid infinite recursion.
env = check.bestEnv(env)
h := env.typeHash(n.orig, n.targs.list())
// ensure that an instance is recorded for h to avoid infinite recursion.
env.typeForHash(h, n)
smap := makeSubstMap(n.orig.tparams.list(), n.targs.list())
underlying = n.check.subst(instPos, n.orig.underlying, smap, env)
for i := 0; i < n.orig.NumMethods(); i++ {
origm := n.orig.Method(i)

31
src/go/types/subst.go
View File

@ -52,24 +52,12 @@ func (check *Checker) subst(pos token.Pos, typ Type, smap substMap, env *Environ
}
// general case
var subst subster
subst.pos = pos
subst.smap = smap
if check != nil {
subst.check = check
if env == nil {
env = check.conf.Environment
}
subst := subster{
pos: pos,
smap: smap,
check: check,
env: check.bestEnv(env),
}
if env == nil {
// If we don't have a *Checker and its global type map,
// use a local version. Besides avoiding duplicate work,
// the type map prevents infinite recursive substitution
// for recursive types (example: type T[P any] *T[P]).
env = NewEnvironment()
}
subst.env = env
return subst.typ(typ)
}
@ -227,11 +215,8 @@ func (subst *subster) typ(typ Type) Type {
// recursion. The position used here is irrelevant because validation only
// occurs on t (we don't call validType on named), but we use subst.pos to
// help with debugging.
named := subst.check.instance(subst.pos, t.orig, newTArgs, subst.env).(*Named)
// TODO(rfindley): we probably don't need to resolve here. Investigate if
// this can be removed.
named.resolve(subst.env)
assert(named.underlying != nil)
t.orig.resolve(subst.env)
return subst.check.instance(subst.pos, t.orig, newTArgs, subst.env)
// Note that if we were to expose substitution more generally (not just in
// the context of a declaration), we'd have to substitute in
@ -239,8 +224,6 @@ func (subst *subster) typ(typ Type) Type {
//
// But this is unnecessary for now.
return named
case *TypeParam:
return subst.smap.lookup(t)