cmd/compile: make sure imported instantiated types have their methods created

We should be putting a newly instantiated imported type in
Instantiate/doInst onto the instTypeList, so its methods/dictionaries
are instantiated. To do this, we needed a more general way to add a
type to instTypeList, so add NeedInstType(), analogous to
NeedRuntimeType(). This has the extra advantage that now all types
created by the type substituter are added to instTypeList without any
extra code, which was easy to forget. doInst() now correctly calls
NeedInstType().

This is a bit aggressive, since a fully instantiated type in a generic
function/method may never be used, if the generic method is never
instantiated in the local package. But it should be fairly uncommon for
a generic method to mention a fully instantiated type (but it does
happen in this bug).

Fixes both cases mentioned in the bug.

Fixed #48185

Change-Id: I19b5012dfac17e306c8005f8595a648b0ab280d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/347909
Trust: Dan Scales <danscales@google.com>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -237,7 +237,6 @@ func (g *irgen) substType(typ *types.Type, tparams *types.Type, targs []ir.Node)
 		Targs:   targs1,
 	}
 	newt := ts.Typ(typ)
-	g.instTypeList = append(g.instTypeList, ts.InstTypeList...)
 	return newt
 }
 

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

@@ -152,9 +152,6 @@ type irgen struct {
 	// types which we need to finish, by doing g.fillinMethods.
 	typesToFinalize []*typeDelayInfo
 
-	// Fully-instantiated generic types whose methods should be instantiated
-	instTypeList []*types.Type
-
 	dnum int // for generating unique dictionary variables
 
 	// Map from generic function to information about its type params, derived

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

@@ -481,10 +481,15 @@ func (g *irgen) buildClosure(outer *ir.Func, x ir.Node) ir.Node {
 }
 
 // instantiateMethods instantiates all the methods (and associated dictionaries) of
-// all fully-instantiated generic types that have been added to g.instTypeList.
+// all fully-instantiated generic types that have been added to typecheck.instTypeList.
+// It continues until no more types are added to typecheck.instTypeList.
 func (g *irgen) instantiateMethods() {
-	for i := 0; i < len(g.instTypeList); i++ {
-		typ := g.instTypeList[i]
+	for {
+		instTypeList := typecheck.GetInstTypeList()
+		if len(instTypeList) == 0 {
+			break
+		}
+		for _, typ := range instTypeList {
 			assert(!typ.HasShape())
 			// Mark runtime type as needed, since this ensures that the
 			// compiler puts out the needed DWARF symbols, when this
@@ -512,8 +517,7 @@ func (g *irgen) instantiateMethods() {
 				_ = g.getDictionarySym(baseNname, typ.RParams(), true)
 			}
 		}
-	g.instTypeList = nil
-
+	}
 }
 
 // getInstNameNode returns the name node for the method or function being instantiated, and a bool which is true if a method is being instantiated.
@@ -735,9 +739,6 @@ func (g *irgen) genericSubst(newsym *types.Sym, nameNode *ir.Name, shapes []*typ
 	}
 
 	ir.CurFunc = savef
-	// Add any new, fully instantiated types seen during the substitution to
-	// g.instTypeList.
-	g.instTypeList = append(g.instTypeList, subst.ts.InstTypeList...)
 
 	if doubleCheck {
 		ir.Visit(newf, func(n ir.Node) {
@@ -1573,7 +1574,6 @@ func (g *irgen) getDictionarySym(gf *ir.Name, targs []*types.Type, isMeth bool)
 		off:   off,
 	}
 	g.dictSymsToFinalize = append(g.dictSymsToFinalize, delay)
-	g.instTypeList = append(g.instTypeList, subst.InstTypeList...)
 	return sym
 }
 
@@ -1640,8 +1640,6 @@ func (g *irgen) finalizeSyms() {
 
 		objw.Global(lsym, int32(d.off), obj.DUPOK|obj.RODATA)
 		infoPrint("=== Finalized dictionary %s\n", d.sym.Name)
-
-		g.instTypeList = append(g.instTypeList, subst.InstTypeList...)
 	}
 	g.dictSymsToFinalize = nil
 }

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

@@ -321,10 +321,6 @@ func (g *irgen) fillinMethods(typ *types2.Named, ntyp *types.Type) {
 				}
 				// Do the substitution of the type
 				meth2.SetType(ts.Typ(meth.Type()))
-				// Add any new fully instantiated types
-				// seen during the substitution to
-				// g.instTypeList.
-				g.instTypeList = append(g.instTypeList, ts.InstTypeList...)
 				newsym.Def = meth2
 			}
 			meth = meth2
@@ -335,7 +331,7 @@ func (g *irgen) fillinMethods(typ *types2.Named, ntyp *types.Type) {
 	ntyp.Methods().Set(methods)
 	if !ntyp.HasTParam() && !ntyp.HasShape() {
 		// Generate all the methods for a new fully-instantiated type.
-		g.instTypeList = append(g.instTypeList, ntyp)
+		typecheck.NeedInstType(ntyp)
 	}
 }
 

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

@@ -1871,4 +1871,8 @@ func substInstType(t *types.Type, baseType *types.Type, targs []*types.Type) {
 		newfields[i].Nname = nname
 	}
 	t.Methods().Set(newfields)
+	if !t.HasTParam() && t.Kind() != types.TINTER && t.Methods().Len() > 0 {
+		// Generate all the methods for a new fully-instantiated type.
+		NeedInstType(t)
+	}
 }

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

@@ -992,6 +992,22 @@ func assert(p bool) {
 	base.Assert(p)
 }
 
+// List of newly fully-instantiated types who should have their methods generated.
+var instTypeList []*types.Type
+
+// NeedInstType adds a new fully-instantied type to instTypeList.
+func NeedInstType(t *types.Type) {
+	instTypeList = append(instTypeList, t)
+}
+
+// GetInstTypeList returns the current contents of instTypeList, and sets
+// instTypeList to nil.
+func GetInstTypeList() []*types.Type {
+	r := instTypeList
+	instTypeList = nil
+	return r
+}
+
 // General type substituter, for replacing typeparams with type args.
 type Tsubster struct {
 	Tparams []*types.Type
@@ -999,8 +1015,6 @@ type Tsubster struct {
 	// If non-nil, the substitution map from name nodes in the generic function to the
 	// name nodes in the new stenciled function.
 	Vars map[*ir.Name]*ir.Name
-	// New fully-instantiated generic types whose methods should be instantiated.
-	InstTypeList []*types.Type
 	// If non-nil, function to substitute an incomplete (TFORW) type.
 	SubstForwFunc func(*types.Type) *types.Type
 }
@@ -1258,7 +1272,8 @@ func (ts *Tsubster) typ1(t *types.Type) *types.Type {
 		newt.Methods().Set(newfields)
 		if !newt.HasTParam() && !newt.HasShape() {
 			// Generate all the methods for a new fully-instantiated type.
-			ts.InstTypeList = append(ts.InstTypeList, newt)
+
+			NeedInstType(newt)
 		}
 	}
 	return newt

test/typeparam/issue48185b.dir/a.go

@@ -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 a
+
+import (
+	"reflect"
+	"sync"
+)
+
+type addressableValue struct{ reflect.Value }
+
+type arshalers[Options, Coder any] struct {
+	fncVals  []typedArshaler[Options, Coder]
+	fncCache sync.Map // map[reflect.Type]unmarshaler
+}
+type typedArshaler[Options, Coder any] struct {
+	typ reflect.Type
+	fnc func(Options, *Coder, addressableValue) error
+}
+
+type UnmarshalOptions1 struct {
+	// Unmarshalers is a list of type-specific unmarshalers to use.
+	Unmarshalers *arshalers[UnmarshalOptions1, Decoder1]
+}
+
+type Decoder1 struct {
+}
+
+func (a *arshalers[Options, Coder]) lookup(fnc func(Options, *Coder, addressableValue) error, t reflect.Type) func(Options, *Coder, addressableValue) error {
+	return fnc
+}
+
+func UnmarshalFuncV2[T any](fn func(UnmarshalOptions1, *Decoder1, T) error) *arshalers[UnmarshalOptions1, Decoder1] {
+	return &arshalers[UnmarshalOptions1, Decoder1]{}
+}

test/typeparam/issue48185b.dir/main.go

@@ -0,0 +1,18 @@
+// 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 (
+	"a"
+	"fmt"
+)
+
+func main() {
+	_ = a.UnmarshalOptions1{
+		Unmarshalers: a.UnmarshalFuncV2(func(opts a.UnmarshalOptions1, dec *a.Decoder1, val *interface{}) (err error) {
+			return fmt.Errorf("error")
+		}),
+	}
+}

test/typeparam/issue48185b.go

@@ -0,0 +1,7 @@
+// rundir -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 ignored