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[dev.typeparams] cmd/compile/internal/types2: ensure that Named.check is nilled out once it is expanded
This is a port of - https://golang.org/cl/318849 - https://golang.org/cl/322974 For #45580. Change-Id: Ie0700ed6c8d472305d5ba7ff97da1ae063152aa3 Reviewed-on: https://go-review.googlesource.com/c/go/+/323030 Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Robert Griesemer <gri@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
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@ -523,15 +523,37 @@ func (check *Checker) varDecl(obj *Var, lhs []*Var, typ, init syntax.Expr) {
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// n0.check != nil, the cycle is reported.
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func (n0 *Named) under() Type {
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u := n0.underlying
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if u == nil {
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return Typ[Invalid]
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if u == Typ[Invalid] {
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return u
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}
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// If the underlying type of a defined type is not a defined
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// type, then that is the desired underlying type.
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// (incl. instance) type, then that is the desired underlying
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// type.
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switch u.(type) {
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case nil:
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return Typ[Invalid]
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default:
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// common case
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return u
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case *Named, *instance:
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// handled below
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}
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if n0.check == nil {
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panic("internal error: Named.check == nil but type is incomplete")
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}
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// Invariant: after this point n0 as well as any named types in its
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// underlying chain should be set up when this function exits.
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check := n0.check
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// If we can't expand u at this point, it is invalid.
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n := asNamed(u)
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if n == nil {
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return u // common case
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n0.underlying = Typ[Invalid]
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return n0.underlying
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}
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// Otherwise, follow the forward chain.
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@ -543,7 +565,16 @@ func (n0 *Named) under() Type {
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u = Typ[Invalid]
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break
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}
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n1 := asNamed(u)
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var n1 *Named
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switch u1 := u.(type) {
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case *Named:
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n1 = u1
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case *instance:
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n1, _ = u1.expand().(*Named)
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if n1 == nil {
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u = Typ[Invalid]
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}
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}
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if n1 == nil {
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break // end of chain
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}
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@ -554,11 +585,7 @@ func (n0 *Named) under() Type {
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if i, ok := seen[n]; ok {
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// cycle
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// TODO(gri) revert this to a method on Checker. Having a possibly
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// nil Checker on Named and TypeParam is too subtle.
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if n0.check != nil {
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n0.check.cycleError(path[i:])
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}
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check.cycleError(path[i:])
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u = Typ[Invalid]
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break
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}
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@ -568,8 +595,8 @@ func (n0 *Named) under() Type {
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// We should never have to update the underlying type of an imported type;
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// those underlying types should have been resolved during the import.
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// Also, doing so would lead to a race condition (was issue #31749).
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// Do this check always, not just in debug more (it's cheap).
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if n0.check != nil && n.obj.pkg != n0.check.pkg {
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// Do this check always, not just in debug mode (it's cheap).
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if n.obj.pkg != check.pkg {
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panic("internal error: imported type with unresolved underlying type")
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}
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n.underlying = u
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@ -134,6 +134,9 @@ func (s sanitizer) typ(typ Type) Type {
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}
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case *Named:
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if debug && t.check != nil {
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panic("internal error: Named.check != nil")
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}
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if orig := s.typ(t.fromRHS); orig != t.fromRHS {
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t.fromRHS = orig
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}
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@ -544,7 +544,7 @@ func (c *Chan) Elem() Type { return c.elem }
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// A Named represents a named (defined) type.
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type Named struct {
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check *Checker // for Named.under implementation
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check *Checker // for Named.under implementation; nilled once under has been called
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info typeInfo // for cycle detection
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obj *TypeName // corresponding declared object
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orig *Named // original, uninstantiated type
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@ -574,6 +574,23 @@ func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tpar
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if obj.typ == nil {
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obj.typ = typ
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}
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// Ensure that typ is always expanded, at which point the check field can be
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// nilled out.
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//
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// Note that currently we cannot nil out check inside typ.under(), because
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// it's possible that typ is expanded multiple times.
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//
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// TODO(gri): clean this up so that under is the only function mutating
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// named types.
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if check != nil {
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check.later(func() {
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switch typ.under().(type) {
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case *Named, *instance:
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panic("internal error: unexpanded underlying type")
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}
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typ.check = nil
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})
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}
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return typ
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}
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