cmd/compile: fix CheckSize() calculation for -G=3 and stencils

Because the Align/Width of pointer types are always set when created,
CalcSize() never descends past a pointer. Therefore, we need to do
CheckSize() at every level when creating type. We need to do this for
types creates by types2-to-types1 conversion and also by type
substitution (mostly for stenciling). We also need to do
Defer/ResumeCheckSize() at the top level in each of these cases to deal
with potentially recursive types.

These changes fix issue #47929 and also allow us to remove the
special-case CheckSize() call that causes the problem for issue #47901.

Fixes #47901
Fixes #47929

Change-Id: Icd8192431c145009cd6df2f4ade6db7da0f4dd3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/344829
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/noder/types.go

@@ -30,21 +30,11 @@ func (g *irgen) pkg(pkg *types2.Package) *types.Pkg {
 // typ converts a types2.Type to a types.Type, including caching of previously
 // translated types.
 func (g *irgen) typ(typ types2.Type) *types.Type {
+	// Defer the CheckSize calls until we have fully-defined a
+	// (possibly-recursive) top-level type.
+	types.DeferCheckSize()
 	res := g.typ1(typ)
-
+	types.ResumeCheckSize()
-	// Calculate the size for all concrete types seen by the frontend. The old
-	// typechecker calls CheckSize() a lot, and we want to eliminate calling
-	// it eventually, so we should do it here instead. We only call it for
-	// top-level types (i.e. we do it here rather in typ1), to make sure that
-	// recursive types have been fully constructed before we call CheckSize.
-	if res != nil && !res.IsUntyped() && !res.IsFuncArgStruct() && !res.HasTParam() {
-		types.CheckSize(res)
-		if res.IsPtr() {
-			// Pointers always have their size set, even though their element
-			// may not have its size set.
-			types.CheckSize(res.Elem())
-		}
-	}
 	return res
 }
 
@@ -59,6 +49,12 @@ func (g *irgen) typ1(typ types2.Type) *types.Type {
 	res, ok := g.typs[typ]
 	if !ok {
 		res = g.typ0(typ)
+		// Calculate the size for all concrete types seen by the frontend.
+		// This is the replacement for the CheckSize() calls in the types1
+		// typechecker. These will be deferred until the top-level g.typ().
+		if res != nil && !res.IsUntyped() && !res.IsFuncArgStruct() && !res.HasTParam() {
+			types.CheckSize(res)
+		}
 		g.typs[typ] = res
 	}
 	return res

src/cmd/compile/internal/typecheck/subr.go

@@ -1003,6 +1003,15 @@ type Tsubster struct {
 // result is t; otherwise the result is a new type. It deals with recursive types
 // by using TFORW types and finding partially or fully created types via sym.Def.
 func (ts *Tsubster) Typ(t *types.Type) *types.Type {
+	// Defer the CheckSize calls until we have fully-defined
+	// (possibly-recursive) top-level type.
+	types.DeferCheckSize()
+	r := ts.typ1(t)
+	types.ResumeCheckSize()
+	return r
+}
+
+func (ts *Tsubster) typ1(t *types.Type) *types.Type {
 	if !t.HasTParam() && t.Kind() != types.TFUNC {
 		// Note: function types need to be copied regardless, as the
 		// types of closures may contain declarations that need
@@ -1047,7 +1056,7 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		// the tparam/targs mapping from subst.
 		neededTargs = make([]*types.Type, len(t.RParams()))
 		for i, rparam := range t.RParams() {
-			neededTargs[i] = ts.Typ(rparam)
+			neededTargs[i] = ts.typ1(rparam)
 			if !types.Identical(neededTargs[i], rparam) {
 				targsChanged = true
 			}
@@ -1085,26 +1094,26 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		}
 		// Substitute the underlying typeparam (e.g. T in P[T], see
 		// the example describing type P[T] above).
-		newt = ts.Typ(t.Underlying())
+		newt = ts.typ1(t.Underlying())
 		assert(newt != t)
 
 	case types.TARRAY:
 		elem := t.Elem()
-		newelem := ts.Typ(elem)
+		newelem := ts.typ1(elem)
 		if newelem != elem || targsChanged {
 			newt = types.NewArray(newelem, t.NumElem())
 		}
 
 	case types.TPTR:
 		elem := t.Elem()
-		newelem := ts.Typ(elem)
+		newelem := ts.typ1(elem)
 		if newelem != elem || targsChanged {
 			newt = types.NewPtr(newelem)
 		}
 
 	case types.TSLICE:
 		elem := t.Elem()
-		newelem := ts.Typ(elem)
+		newelem := ts.typ1(elem)
 		if newelem != elem || targsChanged {
 			newt = types.NewSlice(newelem)
 		}
@@ -1159,22 +1168,17 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		}
 
 	case types.TMAP:
-		newkey := ts.Typ(t.Key())
+		newkey := ts.typ1(t.Key())
-		newval := ts.Typ(t.Elem())
+		newval := ts.typ1(t.Elem())
 		if newkey != t.Key() || newval != t.Elem() || targsChanged {
 			newt = types.NewMap(newkey, newval)
 		}
 
 	case types.TCHAN:
 		elem := t.Elem()
-		newelem := ts.Typ(elem)
+		newelem := ts.typ1(elem)
 		if newelem != elem || targsChanged {
 			newt = types.NewChan(newelem, t.ChanDir())
-			if !newt.HasTParam() {
-				// TODO(danscales): not sure why I have to do this
-				// only for channels.....
-				types.CheckSize(newt)
-			}
 		}
 	case types.TFORW:
 		if ts.SubstForwFunc != nil {
@@ -1194,7 +1198,7 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		for i := 0; i < nt; i++ {
 			term, tilde := t.Term(i)
 			tildes[i] = tilde
-			newterms[i] = ts.Typ(term)
+			newterms[i] = ts.typ1(term)
 			if newterms[i] != term {
 				changed = true
 			}
@@ -1212,24 +1216,24 @@ func (ts *Tsubster) Typ(t *types.Type) *types.Type {
 		return t
 	}
 
-	if t.Sym() == nil && t.Kind() != types.TINTER {
-		// Not a named type or interface type, so there was no forwarding type
-		// and there are no methods to substitute.
-		assert(t.Methods().Len() == 0)
-		return newt
-	}
-
 	if forw != nil {
 		forw.SetUnderlying(newt)
 		newt = forw
 	}
 
+	if !newt.HasTParam() {
+		// Calculate the size of any new types created. These will be
+		// deferred until the top-level ts.Typ() or g.typ() (if this is
+		// called from g.fillinMethods()).
+		types.CheckSize(newt)
+	}
+
 	if t.Kind() != types.TINTER && t.Methods().Len() > 0 {
 		// Fill in the method info for the new type.
 		var newfields []*types.Field
 		newfields = make([]*types.Field, t.Methods().Len())
 		for i, f := range t.Methods().Slice() {
-			t2 := ts.Typ(f.Type)
+			t2 := ts.typ1(f.Type)
 			oldsym := f.Nname.Sym()
 			newsym := MakeFuncInstSym(oldsym, ts.Targs, true)
 			var nname *ir.Name
@@ -1272,7 +1276,7 @@ func (ts *Tsubster) tstruct(t *types.Type, force bool) *types.Type {
 		newfields = make([]*types.Field, t.NumFields())
 	}
 	for i, f := range t.Fields().Slice() {
-		t2 := ts.Typ(f.Type)
+		t2 := ts.typ1(f.Type)
 		if (t2 != f.Type || f.Nname != nil) && newfields == nil {
 			newfields = make([]*types.Field, t.NumFields())
 			for j := 0; j < i; j++ {
@@ -1325,7 +1329,7 @@ func (ts *Tsubster) tinter(t *types.Type) *types.Type {
 	}
 	var newfields []*types.Field
 	for i, f := range t.Methods().Slice() {
-		t2 := ts.Typ(f.Type)
+		t2 := ts.typ1(f.Type)
 		if (t2 != f.Type || f.Nname != nil) && newfields == nil {
 			newfields = make([]*types.Field, t.Methods().Len())
 			for j := 0; j < i; j++ {

test/typeparam/issue47901.go

@@ -0,0 +1,21 @@
+// run -gcflags=-G=3
+
+// 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
+
+type Chan[T any] chan Chan[T]
+
+func (ch Chan[T]) recv() Chan[T] {
+	return <-ch
+}
+
+func main() {
+	ch := Chan[int](make(chan Chan[int]))
+	go func() {
+		ch <- make(Chan[int])
+	}()
+	ch.recv()
+}

test/typeparam/issue47929.go

@@ -0,0 +1,29 @@
+// compile -G=3 -p=p
+
+// 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 v4
+
+var sink interface{}
+
+//go:noinline
+func Do(result, body interface{}) {
+	sink = &result
+}
+
+func DataAction(result DataActionResponse, body DataActionRequest) {
+	Do(&result, body)
+}
+
+type DataActionRequest struct {
+	Action *interface{}
+}
+
+type DataActionResponse struct {
+	ValidationErrors *ValidationError
+}
+
+type ValidationError struct {
+}