[dev.typeparams] cmd/compile: get export/import of generic types & functions working

The general idea is that we now export/import typeparams, typeparam
lists for generic types and functions, and instantiated types
(instantiations of generic types with either new typeparams or concrete
types).

This changes the export format -- the next CL in the stack adds the
export versions and checks for it in the appropriate places.

We always export/import generic function bodies, using the same code
that we use for exporting/importing the bodies of inlineable functions.

To avoid complicated scoping, we consider all type params as unique and
give them unique names for types1. We therefore include the types2 ids
(subscripts) in the export format and re-create on import. We always
access the same unique types1 typeParam type for the same typeparam
name.

We create fully-instantiated generic types and functions in the original
source package. We do an extra NeedRuntimeType() call to make sure that
the correct DWARF information is written out. We call SetDupOK(true) for
the functions/methods to have the linker automatically drop duplicate
instantiations.

Other miscellaneous details:
 - Export/import of typeparam bounds works for methods (but not
   typelists) for now, but will change with the typeset changes.

 - Added a new types.Instantiate function roughly analogous to the
   types2.Instantiate function recently added.

 - Always access methods info from the original/base generic type, since
   the methods of an instantiated type are not filled in (in types2 or
   types1).

 - New field OrigSym in types.Type to keep track of base generic type
   that instantiated type was based on. We use the generic type's symbol
   (OrigSym) as the link, rather than a Type pointer, since we haven't
   always created the base type yet when we want to set the link (during
   types2 to types1 conversion).

 - Added types2.AsTypeParam(), (*types2.TypeParam).SetId()

 - New test minimp.dir, which tests use of generic function Min across
   packages. Another test stringimp.dir, which also exports a generic
   function Stringify across packages, where the type param has a bound
   (Stringer) as well. New test pairimp.dir, which tests use of generic
   type Pair (with no methods) across packages.

 - New test valimp.dir, which tests use of generic type (with methods
   and related functions) across packages.

 - Modified several other tests (adder.go, settable.go, smallest.go,
   stringable.go, struct.go, sum.go) to export their generic
   functions/types to show that generic functions/types can be exported
   successfully (but this doesn't test import).

Change-Id: Ie61ce9d54a46d368ddc7a76c41399378963bb57f
Reviewed-on: https://go-review.googlesource.com/c/go/+/319930
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

17 files changed, 481 insertions, 115 deletions

diff --git a/src/cmd/compile/internal/gc/export.go b/src/cmd/compile/internal/gc/export.go
index 2137f1d196..e19d52fa95 100644
--- a/src/cmd/compile/internal/gc/export.go
+++ b/src/cmd/compile/internal/gc/export.go
@@ -25,11 +25,6 @@ func exportf(bout *bio.Writer, format string, args ...interface{}) {
 func dumpexport(bout *bio.Writer) {
 	p := &exporter{marked: make(map[*types.Type]bool)}
 	for _, n := range typecheck.Target.Exports {
-		// Must catch it here rather than Export(), because the type can be
-		// not fully set (still TFORW) when Export() is called.
-		if n.Type() != nil && n.Type().HasTParam() {
-			base.Fatalf("Cannot (yet) export a generic type: %v", n)
-		}
 		p.markObject(n)
 	}
 
@@ -103,6 +98,11 @@ func (p *exporter) markType(t *types.Type) {
 		return
 	}
 	p.marked[t] = true
+	if t.HasTParam() {
+		// Don't deal with any generic types or their methods, since we
+		// will only be inlining actual instantiations, not generic methods.
+		return
+	}
 
 	// If this is a named type, mark all of its associated
 	// methods. Skip interface types because t.Methods contains
@@ -152,6 +152,8 @@ func (p *exporter) markType(t *types.Type) {
 		}
 
 	case types.TINTER:
+		// TODO(danscales) - will have to deal with the types in interface
+		// elements here when implemented in types2 and represented in types1.
 		for _, f := range t.AllMethods().Slice() {
 			if types.IsExported(f.Sym.Name) {
 				p.markType(f.Type)
diff --git a/src/cmd/compile/internal/importer/iimport.go b/src/cmd/compile/internal/importer/iimport.go
index b91b209d35..a4637ec34f 100644
--- a/src/cmd/compile/internal/importer/iimport.go
+++ b/src/cmd/compile/internal/importer/iimport.go
@@ -57,6 +57,8 @@ const (
 	signatureType
 	structType
 	interfaceType
+	typeParamType
+	instType
 )
 
 const io_SeekCurrent = 1 // io.SeekCurrent (not defined in Go 1.4)
@@ -292,15 +294,20 @@ func (r *importReader) obj(name string) {
 		r.declare(types2.NewConst(pos, r.currPkg, name, typ, val))
 
 	case 'F':
+		tparams := r.tparamList()
 		sig := r.signature(nil)
+		sig.SetTParams(tparams)
 
 		r.declare(types2.NewFunc(pos, r.currPkg, name, sig))
 
 	case 'T':
+		tparams := r.tparamList()
+
 		// Types can be recursive. We need to setup a stub
 		// declaration before recursing.
 		obj := types2.NewTypeName(pos, r.currPkg, name, nil)
 		named := types2.NewNamed(obj, nil, nil)
+		named.SetTParams(tparams)
 		r.declare(obj)
 
 		underlying := r.p.typAt(r.uint64(), named).Underlying()
@@ -313,6 +320,18 @@ func (r *importReader) obj(name string) {
 				recv := r.param()
 				msig := r.signature(recv)
 
+				// If the receiver has any targs, set those as the
+				// rparams of the method (since those are the
+				// typeparams being used in the method sig/body).
+				targs := baseType(msig.Recv().Type()).TArgs()
+				if len(targs) > 0 {
+					rparams := make([]*types2.TypeName, len(targs))
+					for i, targ := range targs {
+						rparams[i] = types2.AsTypeParam(targ).Obj()
+					}
+					msig.SetRParams(rparams)
+				}
+
 				named.AddMethod(types2.NewFunc(mpos, r.currPkg, mname, msig))
 			}
 		}
@@ -571,6 +590,49 @@ func (r *importReader) doType(base *types2.Named) types2.Type {
 		typ := types2.NewInterfaceType(methods, embeddeds)
 		r.p.interfaceList = append(r.p.interfaceList, typ)
 		return typ
+
+	case typeParamType:
+		r.currPkg = r.pkg()
+		pos := r.pos()
+		name := r.string()
+
+		// Extract the subscript value from the type param name. We export
+		// and import the subscript value, so that all type params have
+		// unique names.
+		sub := uint64(0)
+		startsub := -1
+		for i, r := range name {
+			if '₀' <= r && r < '₀'+10 {
+				if startsub == -1 {
+					startsub = i
+				}
+				sub = sub*10 + uint64(r-'₀')
+			}
+		}
+		if startsub >= 0 {
+			name = name[:startsub]
+		}
+		index := int(r.int64())
+		bound := r.typ()
+		tn := types2.NewTypeName(pos, r.currPkg, name, nil)
+		t := (*types2.Checker)(nil).NewTypeParam(tn, index, bound)
+		if sub >= 0 {
+			t.SetId(sub)
+		}
+		return t
+
+	case instType:
+		pos := r.pos()
+		len := r.uint64()
+		targs := make([]types2.Type, len)
+		for i := range targs {
+			targs[i] = r.typ()
+		}
+		baseType := r.typ()
+		// The imported instantiated type doesn't include any methods, so
+		// we must always use the methods of the base (orig) type.
+		t := types2.Instantiate(pos, baseType, targs)
+		return t
 	}
 }
 
@@ -585,6 +647,19 @@ func (r *importReader) signature(recv *types2.Var) *types2.Signature {
 	return types2.NewSignature(recv, params, results, variadic)
 }
 
+func (r *importReader) tparamList() []*types2.TypeName {
+	n := r.uint64()
+	if n == 0 {
+		return nil
+	}
+	xs := make([]*types2.TypeName, n)
+	for i := range xs {
+		typ := r.typ()
+		xs[i] = types2.AsTypeParam(typ).Obj()
+	}
+	return xs
+}
+
 func (r *importReader) paramList() *types2.Tuple {
 	xs := make([]*types2.Var, r.uint64())
 	for i := range xs {
@@ -627,3 +702,13 @@ func (r *importReader) byte() byte {
 	}
 	return x
 }
+
+func baseType(typ types2.Type) *types2.Named {
+	// pointer receivers are never types2.Named types
+	if p, _ := typ.(*types2.Pointer); p != nil {
+		typ = p.Elem()
+	}
+	// receiver base types are always (possibly generic) types2.Named types
+	n, _ := typ.(*types2.Named)
+	return n
+}
diff --git a/src/cmd/compile/internal/noder/decl.go b/src/cmd/compile/internal/noder/decl.go
index 3e55437afa..40cbe50aff 100644
--- a/src/cmd/compile/internal/noder/decl.go
+++ b/src/cmd/compile/internal/noder/decl.go
@@ -148,11 +148,15 @@ func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
 	// [mdempsky: Subtleties like these are why I always vehemently
 	// object to new type pragmas.]
 	ntyp.SetUnderlying(g.typeExpr(decl.Type))
-	if len(decl.TParamList) > 0 {
-		// Set HasTParam if there are any tparams, even if no tparams are
-		// used in the type itself (e.g., if it is an empty struct, or no
-		// fields in the struct use the tparam).
-		ntyp.SetHasTParam(true)
+
+	tparams := otyp.(*types2.Named).TParams()
+	if len(tparams) > 0 {
+		rparams := make([]*types.Type, len(tparams))
+		for i := range rparams {
+			rparams[i] = g.typ(tparams[i].Type())
+		}
+		// This will set hasTParam flag if any rparams are not concrete types.
+		ntyp.SetRParams(rparams)
 	}
 	types.ResumeCheckSize()
 
diff --git a/src/cmd/compile/internal/noder/expr.go b/src/cmd/compile/internal/noder/expr.go
index b7f7a34953..f96144f8d7 100644
--- a/src/cmd/compile/internal/noder/expr.go
+++ b/src/cmd/compile/internal/noder/expr.go
@@ -264,8 +264,12 @@ func (g *irgen) selectorExpr(pos src.XPos, typ types2.Type, expr *syntax.Selecto
 				// instantiated for this method call.
 				// selinfo.Recv() is the instantiated type
 				recvType2 = recvType2Base
-				// method is the generic method associated with the gen type
-				method := g.obj(types2.AsNamed(recvType2).Method(last))
+				recvTypeSym := g.pkg(method2.Pkg()).Lookup(recvType2.(*types2.Named).Obj().Name())
+				recvType := recvTypeSym.Def.(*ir.Name).Type()
+				// method is the generic method associated with
+				// the base generic type. The instantiated type may not
+				// have method bodies filled in, if it was imported.
+				method := recvType.Methods().Index(last).Nname.(*ir.Name)
 				n = ir.NewSelectorExpr(pos, ir.OCALLPART, x, typecheck.Lookup(expr.Sel.Value))
 				n.(*ir.SelectorExpr).Selection = types.NewField(pos, method.Sym(), method.Type())
 				n.(*ir.SelectorExpr).Selection.Nname = method
diff --git a/src/cmd/compile/internal/noder/irgen.go b/src/cmd/compile/internal/noder/irgen.go
index 2a9f0e99d8..f02246111f 100644
--- a/src/cmd/compile/internal/noder/irgen.go
+++ b/src/cmd/compile/internal/noder/irgen.go
@@ -185,9 +185,9 @@ Outer:
 	// Create any needed stencils of generic functions
 	g.stencil()
 
-	// For now, remove all generic functions from g.target.Decl, since they
-	// have been used for stenciling, but don't compile. TODO: We will
-	// eventually export any exportable generic functions.
+	// Remove all generic functions from g.target.Decl, since they have been
+	// used for stenciling, but don't compile. Generic functions will already
+	// have been marked for export as appropriate.
 	j := 0
 	for i, decl := range g.target.Decls {
 		if decl.Op() != ir.ODCLFUNC || !decl.Type().HasTParam() {
diff --git a/src/cmd/compile/internal/noder/object.go b/src/cmd/compile/internal/noder/object.go
index 7af2fe6715..a1a10e4eaa 100644
--- a/src/cmd/compile/internal/noder/object.go
+++ b/src/cmd/compile/internal/noder/object.go
@@ -49,6 +49,11 @@ func (g *irgen) obj(obj types2.Object) *ir.Name {
 	// For imported objects, we use iimport directly instead of mapping
 	// the types2 representation.
 	if obj.Pkg() != g.self {
+		if sig, ok := obj.Type().(*types2.Signature); ok && sig.Recv() != nil {
+			// We can't import a method by name - must import the type
+			// and access the method from it.
+			base.FatalfAt(g.pos(obj), "tried to import a method directly")
+		}
 		sym := g.sym(obj)
 		if sym.Def != nil {
 			return sym.Def.(*ir.Name)
@@ -165,9 +170,8 @@ func (g *irgen) objFinish(name *ir.Name, class ir.Class, typ *types.Type) {
 			break // methods are exported with their receiver type
 		}
 		if types.IsExported(sym.Name) {
-			if name.Class == ir.PFUNC && name.Type().NumTParams() > 0 {
-				base.FatalfAt(name.Pos(), "Cannot export a generic function (yet): %v", name)
-			}
+			// Generic functions can be marked for export here, even
+			// though they will not be compiled until instantiated.
 			typecheck.Export(name)
 		}
 		if base.Flag.AsmHdr != "" && !name.Sym().Asm() {
diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index f9cf6d8a1a..7a7c05280d 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -8,12 +8,10 @@
 package noder
 
 import (
-	"bytes"
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
-	"cmd/internal/src"
 	"fmt"
 	"strings"
 )
@@ -160,9 +158,14 @@ func (g *irgen) stencil() {
 func (g *irgen) instantiateMethods() {
 	for i := 0; i < len(g.instTypeList); i++ {
 		typ := g.instTypeList[i]
-		// Get the base generic type by looking up the symbol of the
-		// generic (uninstantiated) name.
-		baseSym := typ.Sym().Pkg.Lookup(genericTypeName(typ.Sym()))
+		// Mark runtime type as needed, since this ensures that the
+		// compiler puts out the needed DWARF symbols, when this
+		// instantiated type has a different package from the local
+		// package.
+		typecheck.NeedRuntimeType(typ)
+		// Lookup the method on the base generic type, since methods may
+		// not be set on imported instantiated types.
+		baseSym := typ.OrigSym
 		baseType := baseSym.Def.(*ir.Name).Type()
 		for j, m := range typ.Methods().Slice() {
 			name := m.Nname.(*ir.Name)
@@ -199,12 +202,24 @@ func (g *irgen) getInstantiationForNode(inst *ir.InstExpr) *ir.Func {
 // with the type arguments targs. If the instantiated function is not already
 // cached, then it calls genericSubst to create the new instantiation.
 func (g *irgen) getInstantiation(nameNode *ir.Name, targs []*types.Type, isMeth bool) *ir.Func {
+	if nameNode.Func.Body == nil && nameNode.Func.Inl != nil {
+		// If there is no body yet but Func.Inl exists, then we can can
+		// import the whole generic body.
+		assert(nameNode.Func.Inl.Cost == 1 && nameNode.Sym().Pkg != types.LocalPkg)
+		typecheck.ImportBody(nameNode.Func)
+		assert(nameNode.Func.Inl.Body != nil)
+		nameNode.Func.Body = nameNode.Func.Inl.Body
+		nameNode.Func.Dcl = nameNode.Func.Inl.Dcl
+	}
 	sym := typecheck.MakeInstName(nameNode.Sym(), targs, isMeth)
 	st := g.target.Stencils[sym]
 	if st == nil {
 		// If instantiation doesn't exist yet, create it and add
 		// to the list of decls.
 		st = g.genericSubst(sym, nameNode, targs, isMeth)
+		// This ensures that the linker drops duplicates of this instantiation.
+		// All just works!
+		st.SetDupok(true)
 		g.target.Stencils[sym] = st
 		g.target.Decls = append(g.target.Decls, st)
 		if base.Flag.W > 1 {
@@ -626,21 +641,6 @@ func (subst *subster) tinter(t *types.Type) *types.Type {
 	return t
 }
 
-// instTypeName creates a name for an instantiated type, based on the name of the
-// generic type and the type args
-func instTypeName(name string, targs []*types.Type) string {
-	b := bytes.NewBufferString(name)
-	b.WriteByte('[')
-	for i, targ := range targs {
-		if i > 0 {
-			b.WriteByte(',')
-		}
-		b.WriteString(targ.String())
-	}
-	b.WriteByte(']')
-	return b.String()
-}
-
 // typ computes the type obtained by substituting any type parameter in t with the
 // corresponding type argument in subst. If t contains no type parameters, the
 // result is t; otherwise the result is a new type. It deals with recursive types
@@ -696,7 +696,7 @@ func (subst *subster) typ(t *types.Type) *types.Type {
 		// already seen this type during this substitution or other
 		// definitions/substitutions.
 		genName := genericTypeName(t.Sym())
-		newsym = t.Sym().Pkg.Lookup(instTypeName(genName, neededTargs))
+		newsym = t.Sym().Pkg.Lookup(typecheck.InstTypeName(genName, neededTargs))
 		if newsym.Def != nil {
 			// We've already created this instantiated defined type.
 			return newsym.Def.Type()
@@ -705,9 +705,13 @@ func (subst *subster) typ(t *types.Type) *types.Type {
 		// In order to deal with recursive generic types, create a TFORW
 		// type initially and set the Def field of its sym, so it can be
 		// found if this type appears recursively within the type.
-		forw = newIncompleteNamedType(t.Pos(), newsym)
+		forw = typecheck.NewIncompleteNamedType(t.Pos(), newsym)
 		//println("Creating new type by sub", newsym.Name, forw.HasTParam())
 		forw.SetRParams(neededTargs)
+		// Copy the OrigSym from the re-instantiated type (which is the sym of
+		// the base generic type).
+		assert(t.OrigSym != nil)
+		forw.OrigSym = t.OrigSym
 	}
 
 	var newt *types.Type
@@ -865,11 +869,14 @@ func (subst *subster) fields(class ir.Class, oldfields []*types.Field, dcl []*ir
 	for j := range oldfields {
 		newfields[j] = oldfields[j].Copy()
 		newfields[j].Type = subst.typ(oldfields[j].Type)
-		// A param field will be missing from dcl if its name is
+		// A PPARAM field will be missing from dcl if its name is
 		// unspecified or specified as "_". So, we compare the dcl sym
-		// with the field sym. If they don't match, this dcl (if there is
-		// one left) must apply to a later field.
-		if i < len(dcl) && dcl[i].Sym() == oldfields[j].Sym {
+		// with the field sym (or sym of the field's Nname node). (Unnamed
+		// results still have a name like ~r2 in their Nname node.) If
+		// they don't match, this dcl (if there is one left) must apply to
+		// a later field.
+		if i < len(dcl) && (dcl[i].Sym() == oldfields[j].Sym ||
+			(oldfields[j].Nname != nil && dcl[i].Sym() == oldfields[j].Nname.Sym())) {
 			newfields[j].Nname = dcl[i]
 			i++
 		}
@@ -884,13 +891,3 @@ func deref(t *types.Type) *types.Type {
 	}
 	return t
 }
-
-// newIncompleteNamedType returns a TFORW type t with name specified by sym, such
-// that t.nod and sym.Def are set correctly.
-func newIncompleteNamedType(pos src.XPos, sym *types.Sym) *types.Type {
-	name := ir.NewDeclNameAt(pos, ir.OTYPE, sym)
-	forw := types.NewNamed(name)
-	name.SetType(forw)
-	sym.Def = name
-	return forw
-}
diff --git a/src/cmd/compile/internal/noder/types.go b/src/cmd/compile/internal/noder/types.go
index 35ba1cd238..7fdad29e16 100644
--- a/src/cmd/compile/internal/noder/types.go
+++ b/src/cmd/compile/internal/noder/types.go
@@ -68,8 +68,10 @@ func instTypeName2(name string, targs []types2.Type) string {
 		if i > 0 {
 			b.WriteByte(',')
 		}
+		// Include package names for all types, including typeparams, to
+		// make sure type arguments are uniquely specified.
 		tname := types2.TypeString(targ,
-			func(*types2.Package) string { return "" })
+			func(pkg *types2.Package) string { return pkg.Name() })
 		if strings.Index(tname, ", ") >= 0 {
 			// types2.TypeString puts spaces after a comma in a type
 			// list, but we don't want spaces in our actual type names
@@ -120,7 +122,7 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 			// which may set HasTParam) before translating the
 			// underlying type itself, so we handle recursion
 			// correctly, including via method signatures.
-			ntyp := newIncompleteNamedType(g.pos(typ.Obj().Pos()), s)
+			ntyp := typecheck.NewIncompleteNamedType(g.pos(typ.Obj().Pos()), s)
 			g.typs[typ] = ntyp
 
 			// If ntyp still has type params, then we must be
@@ -143,6 +145,8 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 
 			ntyp.SetUnderlying(g.typ1(typ.Underlying()))
 			g.fillinMethods(typ, ntyp)
+			// Save the symbol for the base generic type.
+			ntyp.OrigSym = g.pkg(typ.Obj().Pkg()).Lookup(typ.Obj().Name())
 			return ntyp
 		}
 		obj := g.obj(typ.Obj())
@@ -206,8 +210,19 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 	case *types2.TypeParam:
 		// Save the name of the type parameter in the sym of the type.
 		// Include the types2 subscript in the sym name
-		sym := g.pkg(typ.Obj().Pkg()).Lookup(types2.TypeString(typ, func(*types2.Package) string { return "" }))
+		pkg := g.tpkg(typ)
+		sym := pkg.Lookup(types2.TypeString(typ, func(*types2.Package) string { return "" }))
+		if sym.Def != nil {
+			// Make sure we use the same type param type for the same
+			// name, whether it is created during types1-import or
+			// this types2-to-types1 translation.
+			return sym.Def.Type()
+		}
 		tp := types.NewTypeParam(sym, typ.Index())
+		nname := ir.NewDeclNameAt(g.pos(typ.Obj().Pos()), ir.OTYPE, sym)
+		sym.Def = nname
+		nname.SetType(tp)
+		tp.SetNod(nname)
 		// Set g.typs[typ] in case the bound methods reference typ.
 		g.typs[typ] = tp
 
@@ -248,12 +263,20 @@ func (g *irgen) fillinMethods(typ *types2.Named, ntyp *types.Type) {
 		methods := make([]*types.Field, typ.NumMethods())
 		for i := range methods {
 			m := typ.Method(i)
-			meth := g.obj(m)
 			recvType := types2.AsSignature(m.Type()).Recv().Type()
 			ptr := types2.AsPointer(recvType)
 			if ptr != nil {
 				recvType = ptr.Elem()
 			}
+			var meth *ir.Name
+			if m.Pkg() != g.self {
+				// Imported methods cannot be loaded by name (what
+				// g.obj() does) - they must be loaded via their
+				// type.
+				meth = g.obj(recvType.(*types2.Named).Obj()).Type().Methods().Index(i).Nname.(*ir.Name)
+			} else {
+				meth = g.obj(m)
+			}
 			if recvType != types2.Type(typ) {
 				// Unfortunately, meth is the type of the method of the
 				// generic type, so we have to do a substitution to get
@@ -343,7 +366,7 @@ func (g *irgen) selector(obj types2.Object) *types.Sym {
 	return pkg.Lookup(name)
 }
 
-// tpkg returns the package that a function, interface, or struct type
+// tpkg returns the package that a function, interface, struct, or typeparam type
 // expression appeared in.
 //
 // Caveat: For the degenerate types "func()", "interface{}", and
@@ -373,6 +396,8 @@ func (g *irgen) tpkg(typ types2.Type) *types.Pkg {
 			if typ.NumExplicitMethods() > 0 {
 				return typ.ExplicitMethod(0)
 			}
+		case *types2.TypeParam:
+			return typ.Obj()
 		}
 		return nil
 	}
diff --git a/src/cmd/compile/internal/reflectdata/reflect.go b/src/cmd/compile/internal/reflectdata/reflect.go
index 8c0e33f6df..f65841b33c 100644
--- a/src/cmd/compile/internal/reflectdata/reflect.go
+++ b/src/cmd/compile/internal/reflectdata/reflect.go
@@ -951,8 +951,12 @@ func writeType(t *types.Type) *obj.LSym {
 	}
 
 	if base.Ctxt.Pkgpath != "runtime" || (tbase != types.Types[tbase.Kind()] && tbase != types.ByteType && tbase != types.RuneType && tbase != types.ErrorType) { // int, float, etc
-		// named types from other files are defined only by those files
-		if tbase.Sym() != nil && tbase.Sym().Pkg != types.LocalPkg {
+		// Named types from other files are defined only by those files.
+		// However, as an exception, we can write out instantiated types
+		// in the local package, even if they may be marked as part of
+		// another package (the package of their base generic type).
+		if tbase.Sym() != nil && tbase.Sym().Pkg != types.LocalPkg &&
+			len(tbase.RParams()) == 0 {
 			if i := typecheck.BaseTypeIndex(t); i >= 0 {
 				lsym.Pkg = tbase.Sym().Pkg.Prefix
 				lsym.SymIdx = int32(i)
diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 3538c4d5a6..11b9755148 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -173,6 +173,8 @@
 //     }
 //
 //
+//  TODO(danscales): fill in doc for 'type TypeParamType' and 'type InstType'
+//
 //     type Signature struct {
 //         Params   []Param
 //         Results  []Param
@@ -244,6 +246,8 @@ const (
 	signatureType
 	structType
 	interfaceType
+	typeParamType
+	instType
 )
 
 const (
@@ -459,6 +463,13 @@ func (p *iexporter) doDecl(n *ir.Name) {
 			// Function.
 			w.tag('F')
 			w.pos(n.Pos())
+			// The tparam list of the function type is the
+			// declaration of the type params. So, write out the type
+			// params right now. Then those type params will be
+			// referenced via their type offset (via typOff) in all
+			// other places in the signature and function that they
+			// are used.
+			w.tparamList(n.Type().TParams().FieldSlice())
 			w.signature(n.Type())
 			w.funcExt(n)
 
@@ -491,6 +502,8 @@ func (p *iexporter) doDecl(n *ir.Name) {
 		w.tag('T')
 		w.pos(n.Pos())
 
+		// Export any new typeparams needed for this type
+		w.typeList(n.Type().RParams())
 		underlying := n.Type().Underlying()
 		if underlying == types.ErrorType.Underlying() {
 			// For "type T error", use error as the
@@ -803,8 +816,49 @@ func (w *exportWriter) startType(k itag) {
 }
 
 func (w *exportWriter) doTyp(t *types.Type) {
-	if t.Sym() != nil {
-		if t.Sym().Pkg == types.BuiltinPkg || t.Sym().Pkg == ir.Pkgs.Unsafe {
+	if t.Kind() == types.TTYPEPARAM {
+		// A typeparam has a name, but doesn't have an underlying type.
+		// Just write out the details of the type param here. All other
+		// uses of this typeparam type will be written out as its unique
+		// type offset.
+		w.startType(typeParamType)
+		s := t.Sym()
+		w.setPkg(s.Pkg, true)
+		w.pos(t.Pos())
+
+		// We are writing out the name with the subscript, so that the
+		// typeparam name is unique.
+		w.string(s.Name)
+		w.int64(int64(t.Index()))
+
+		w.typ(t.Bound())
+		return
+	}
+
+	s := t.Sym()
+	if s != nil && t.OrigSym != nil {
+		// This is an instantiated type - could be a re-instantiation like
+		// Value[T2] or a full instantiation like Value[int].
+		if strings.Index(s.Name, "[") < 0 {
+			base.Fatalf("incorrect name for instantiated type")
+		}
+		w.startType(instType)
+		w.pos(t.Pos())
+		// Export the type arguments for the instantiated type. The
+		// instantiated type could be in a method header (e.g. "func (v
+		// *Value[T2]) set (...) { ... }"), so the type args are "new"
+		// typeparams. Or the instantiated type could be in a
+		// function/method body, so the type args are either concrete
+		// types or existing typeparams from the function/method header.
+		w.typeList(t.RParams())
+		// Export a reference to the base type.
+		baseType := t.OrigSym.Def.(*ir.Name).Type()
+		w.typ(baseType)
+		return
+	}
+
+	if s != nil {
+		if s.Pkg == types.BuiltinPkg || s.Pkg == ir.Pkgs.Unsafe {
 			base.Fatalf("builtin type missing from typIndex: %v", t)
 		}
 
@@ -906,6 +960,23 @@ func (w *exportWriter) signature(t *types.Type) {
 	}
 }
 
+func (w *exportWriter) typeList(ts []*types.Type) {
+	w.uint64(uint64(len(ts)))
+	for _, rparam := range ts {
+		w.typ(rparam)
+	}
+}
+
+func (w *exportWriter) tparamList(fs []*types.Field) {
+	w.uint64(uint64(len(fs)))
+	for _, f := range fs {
+		if f.Type.Kind() != types.TTYPEPARAM {
+			base.Fatalf("unexpected non-typeparam")
+		}
+		w.typ(f.Type)
+	}
+}
+
 func (w *exportWriter) paramList(fs []*types.Field) {
 	w.uint64(uint64(len(fs)))
 	for _, f := range fs {
@@ -1186,9 +1257,21 @@ func (w *exportWriter) funcExt(n *ir.Name) {
 	}
 
 	// Inline body.
+	if n.Type().HasTParam() {
+		if n.Func.Inl != nil {
+			base.FatalfAt(n.Pos(), "generic function is marked inlineable")
+		}
+		// Populate n.Func.Inl, so body of exported generic function will
+		// be written out.
+		n.Func.Inl = &ir.Inline{
+			Cost: 1,
+			Dcl:  n.Func.Dcl,
+			Body: n.Func.Body,
+		}
+	}
 	if n.Func.Inl != nil {
 		w.uint64(1 + uint64(n.Func.Inl.Cost))
-		if n.Func.ExportInline() {
+		if n.Func.ExportInline() || n.Type().HasTParam() {
 			w.p.doInline(n)
 		}
 
@@ -1588,9 +1671,8 @@ func (w *exportWriter) expr(n ir.Node) {
 	case ir.OXDOT, ir.ODOT, ir.ODOTPTR, ir.ODOTINTER, ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
 		n := n.(*ir.SelectorExpr)
 		if go117ExportTypes {
-			if n.Op() == ir.OXDOT {
-				base.Fatalf("shouldn't encounter XDOT  in new exporter")
-			}
+			// For go117ExportTypes, we usually see all ops except
+			// OXDOT, but we can see OXDOT for generic functions.
 			w.op(n.Op())
 		} else {
 			w.op(ir.OXDOT)
@@ -1604,7 +1686,8 @@ func (w *exportWriter) expr(n ir.Node) {
 				w.exoticField(n.Selection)
 			}
 			// n.Selection is not required for OMETHEXPR, ODOTMETH, and OCALLPART. It will
-			// be reconstructed during import.
+			// be reconstructed during import.  n.Selection is computed during
+			// transformDot() for OXDOT.
 		}
 
 	case ir.ODOTTYPE, ir.ODOTTYPE2:
diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index a5ddbb5a74..b6f227bb00 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -8,6 +8,7 @@
 package typecheck
 
 import (
+	"bytes"
 	"encoding/binary"
 	"fmt"
 	"go/constant"
@@ -313,13 +314,16 @@ func (r *importReader) doDecl(sym *types.Sym) *ir.Name {
 		return n
 
 	case 'F':
-		typ := r.signature(nil)
+		tparams := r.tparamList()
+		typ := r.signature(nil, tparams)
 
 		n := importfunc(r.p.ipkg, pos, sym, typ)
 		r.funcExt(n)
 		return n
 
 	case 'T':
+		rparams := r.typeList()
+
 		// Types can be recursive. We need to setup a stub
 		// declaration before recursing.
 		n := importtype(r.p.ipkg, pos, sym)
@@ -332,6 +336,10 @@ func (r *importReader) doDecl(sym *types.Sym) *ir.Name {
 		t.SetUnderlying(underlying)
 		types.ResumeCheckSize()
 
+		if rparams != nil {
+			t.SetRParams(rparams)
+		}
+
 		if underlying.IsInterface() {
 			r.typeExt(t)
 			return n
@@ -342,7 +350,7 @@ func (r *importReader) doDecl(sym *types.Sym) *ir.Name {
 			mpos := r.pos()
 			msym := r.selector()
 			recv := r.param()
-			mtyp := r.signature(recv)
+			mtyp := r.signature(recv, nil)
 
 			// MethodSym already marked m.Sym as a function.
 			m := ir.NewNameAt(mpos, ir.MethodSym(recv.Type, msym))
@@ -680,7 +688,7 @@ func (r *importReader) typ1() *types.Type {
 
 	case signatureType:
 		r.setPkg()
-		return r.signature(nil)
+		return r.signature(nil, nil)
 
 	case structType:
 		r.setPkg()
@@ -718,7 +726,7 @@ func (r *importReader) typ1() *types.Type {
 		for i := range methods {
 			pos := r.pos()
 			sym := r.selector()
-			typ := r.signature(fakeRecvField())
+			typ := r.signature(fakeRecvField(), nil)
 
 			methods[i] = types.NewField(pos, sym, typ)
 		}
@@ -728,6 +736,40 @@ func (r *importReader) typ1() *types.Type {
 		// Ensure we expand the interface in the frontend (#25055).
 		types.CheckSize(t)
 		return t
+
+	case typeParamType:
+		r.setPkg()
+		pos := r.pos()
+		name := r.string()
+		sym := r.currPkg.Lookup(name)
+		index := int(r.int64())
+		bound := r.typ()
+		if sym.Def != nil {
+			// Make sure we use the same type param type for the same
+			// name, whether it is created during types1-import or
+			// this types2-to-types1 translation.
+			return sym.Def.Type()
+		}
+		t := types.NewTypeParam(sym, index)
+		// Nname needed to save the pos.
+		nname := ir.NewDeclNameAt(pos, ir.OTYPE, sym)
+		sym.Def = nname
+		nname.SetType(t)
+		t.SetNod(nname)
+
+		t.SetBound(bound)
+		return t
+
+	case instType:
+		pos := r.pos()
+		len := r.uint64()
+		targs := make([]*types.Type, len)
+		for i := range targs {
+			targs[i] = r.typ()
+		}
+		baseType := r.typ()
+		t := Instantiate(pos, baseType, targs)
+		return t
 	}
 }
 
@@ -735,13 +777,38 @@ func (r *importReader) kind() itag {
 	return itag(r.uint64())
 }
 
-func (r *importReader) signature(recv *types.Field) *types.Type {
+func (r *importReader) signature(recv *types.Field, tparams []*types.Field) *types.Type {
 	params := r.paramList()
 	results := r.paramList()
 	if n := len(params); n > 0 {
 		params[n-1].SetIsDDD(r.bool())
 	}
-	return types.NewSignature(r.currPkg, recv, nil, params, results)
+	return types.NewSignature(r.currPkg, recv, tparams, params, results)
+}
+
+func (r *importReader) typeList() []*types.Type {
+	n := r.uint64()
+	if n == 0 {
+		return nil
+	}
+	ts := make([]*types.Type, n)
+	for i := range ts {
+		ts[i] = r.typ()
+	}
+	return ts
+}
+
+func (r *importReader) tparamList() []*types.Field {
+	n := r.uint64()
+	if n == 0 {
+		return nil
+	}
+	fs := make([]*types.Field, n)
+	for i := range fs {
+		typ := r.typ()
+		fs[i] = types.NewField(typ.Pos(), typ.Sym(), typ)
+	}
+	return fs
 }
 
 func (r *importReader) paramList() []*types.Field {
@@ -809,7 +876,9 @@ func (r *importReader) funcExt(n *ir.Name) {
 
 	n.Func.ABI = obj.ABI(r.uint64())
 
-	n.SetPragma(ir.PragmaFlag(r.uint64()))
+	// Make sure //go:noinline pragma is imported (so stenciled functions have
+	// same noinline status as the corresponding generic function.)
+	n.Func.Pragma = ir.PragmaFlag(r.uint64())
 
 	// Escape analysis.
 	for _, fs := range &types.RecvsParams {
@@ -1117,7 +1186,7 @@ func (r *importReader) node() ir.Node {
 	case ir.OCLOSURE:
 		//println("Importing CLOSURE")
 		pos := r.pos()
-		typ := r.signature(nil)
+		typ := r.signature(nil, nil)
 
 		// All the remaining code below is similar to (*noder).funcLit(), but
 		// with Dcls and ClosureVars lists already set up
@@ -1202,35 +1271,32 @@ func (r *importReader) node() ir.Node {
 	// case OSTRUCTKEY:
 	//	unreachable - handled in case OSTRUCTLIT by elemList
 
-	case ir.OXDOT:
-		// see parser.new_dotname
-		if go117ExportTypes {
-			base.Fatalf("shouldn't encounter XDOT in new importer")
-		}
-		return ir.NewSelectorExpr(r.pos(), ir.OXDOT, r.expr(), r.exoticSelector())
-
-	case ir.ODOT, ir.ODOTPTR, ir.ODOTINTER, ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
-		if !go117ExportTypes {
-			// unreachable - mapped to case OXDOT by exporter
+	case ir.OXDOT, ir.ODOT, ir.ODOTPTR, ir.ODOTINTER, ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
+		// For !go117ExportTypes,  we should only see OXDOT.
+		// For go117ExportTypes, we usually see all the other ops, but can see
+		// OXDOT for generic functions.
+		if op != ir.OXDOT && !go117ExportTypes {
 			goto error
 		}
 		pos := r.pos()
 		expr := r.expr()
 		sel := r.exoticSelector()
 		n := ir.NewSelectorExpr(pos, op, expr, sel)
-		n.SetType(r.exoticType())
-		switch op {
-		case ir.ODOT, ir.ODOTPTR, ir.ODOTINTER:
-			n.Selection = r.exoticField()
-		case ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
-			// These require a Lookup to link to the correct declaration.
-			rcvrType := expr.Type()
-			typ := n.Type()
-			n.Selection = Lookdot(n, rcvrType, 1)
-			if op == ir.OCALLPART || op == ir.OMETHEXPR {
-				// Lookdot clobbers the opcode and type, undo that.
-				n.SetOp(op)
-				n.SetType(typ)
+		if go117ExportTypes {
+			n.SetType(r.exoticType())
+			switch op {
+			case ir.ODOT, ir.ODOTPTR, ir.ODOTINTER:
+				n.Selection = r.exoticField()
+			case ir.ODOTMETH, ir.OCALLPART, ir.OMETHEXPR:
+				// These require a Lookup to link to the correct declaration.
+				rcvrType := expr.Type()
+				typ := n.Type()
+				n.Selection = Lookdot(n, rcvrType, 1)
+				if op == ir.OCALLPART || op == ir.OMETHEXPR {
+					// Lookdot clobbers the opcode and type, undo that.
+					n.SetOp(op)
+					n.SetType(typ)
+				}
 			}
 		}
 		return n
@@ -1544,3 +1610,63 @@ func builtinCall(pos src.XPos, op ir.Op) *ir.CallExpr {
 	}
 	return ir.NewCallExpr(pos, ir.OCALL, ir.NewIdent(base.Pos, types.BuiltinPkg.Lookup(ir.OpNames[op])), nil)
 }
+
+// InstTypeName creates a name for an instantiated type, based on the name of the
+// generic type and the type args.
+func InstTypeName(name string, targs []*types.Type) string {
+	b := bytes.NewBufferString(name)
+	b.WriteByte('[')
+	for i, targ := range targs {
+		if i > 0 {
+			b.WriteByte(',')
+		}
+		// WriteString() does not include the package name for the local
+		// package, but we want it to make sure type arguments (including
+		// type params) are uniquely specified.
+		if targ.Sym() != nil && targ.Sym().Pkg == types.LocalPkg {
+			b.WriteString(targ.Sym().Pkg.Name)
+			b.WriteByte('.')
+		}
+		b.WriteString(targ.String())
+	}
+	b.WriteByte(']')
+	return b.String()
+}
+
+// NewIncompleteNamedType returns a TFORW type t with name specified by sym, such
+// that t.nod and sym.Def are set correctly.
+func NewIncompleteNamedType(pos src.XPos, sym *types.Sym) *types.Type {
+	name := ir.NewDeclNameAt(pos, ir.OTYPE, sym)
+	forw := types.NewNamed(name)
+	name.SetType(forw)
+	sym.Def = name
+	return forw
+}
+
+// Instantiate creates a new named type which is the instantiation of the base
+// named generic type, with the specified type args.
+func Instantiate(pos src.XPos, baseType *types.Type, targs []*types.Type) *types.Type {
+	baseSym := baseType.Sym()
+	if strings.Index(baseSym.Name, "[") >= 0 {
+		base.Fatalf("arg to Instantiate is not a base generic type")
+	}
+	name := InstTypeName(baseSym.Name, targs)
+	instSym := baseSym.Pkg.Lookup(name)
+	if instSym.Def != nil {
+		return instSym.Def.Type()
+	}
+
+	t := NewIncompleteNamedType(baseType.Pos(), instSym)
+	t.SetRParams(targs)
+	// baseType may not yet be complete (since we are in the middle of
+	// importing it), but its underlying type will be updated when baseType's
+	// underlying type is finished.
+	t.SetUnderlying(baseType.Underlying())
+
+	// As with types2, the methods are the generic method signatures (without
+	// substitution).
+	t.Methods().Set(baseType.Methods().Slice())
+	t.OrigSym = baseSym
+
+	return t
+}
diff --git a/src/cmd/compile/internal/typecheck/subr.go b/src/cmd/compile/internal/typecheck/subr.go
index 97fb145132..9eac802dab 100644
--- a/src/cmd/compile/internal/typecheck/subr.go
+++ b/src/cmd/compile/internal/typecheck/subr.go
@@ -887,7 +887,7 @@ func TypesOf(x []ir.Node) []*types.Type {
 }
 
 // MakeInstName makes the unique name for a stenciled generic function or method,
-// based on the name of the function fy=nsym and the targs. It replaces any
+// based on the name of the function fnsym and the targs. It replaces any
 // existing bracket type list in the name. makeInstName asserts that fnsym has
 // brackets in its name if and only if hasBrackets is true.
 // TODO(danscales): remove the assertions and the hasBrackets argument later.
@@ -914,6 +914,12 @@ func MakeInstName(fnsym *types.Sym, targs []*types.Type, hasBrackets bool) *type
 		if i > 0 {
 			b.WriteString(",")
 		}
+		// WriteString() does not include the package name for the local
+		// package, but we want it for uniqueness.
+		if targ.Sym() != nil && targ.Sym().Pkg == types.LocalPkg {
+			b.WriteString(targ.Sym().Pkg.Name)
+			b.WriteByte('.')
+		}
 		b.WriteString(targ.String())
 	}
 	b.WriteString("]")
@@ -922,7 +928,7 @@ func MakeInstName(fnsym *types.Sym, targs []*types.Type, hasBrackets bool) *type
 		assert(i2 >= 0)
 		b.WriteString(name[i+i2+1:])
 	}
-	return Lookup(b.String())
+	return fnsym.Pkg.Lookup(b.String())
 }
 
 // For catching problems as we add more features
diff --git a/src/cmd/compile/internal/types/sizeof_test.go b/src/cmd/compile/internal/types/sizeof_test.go
index 7028938742..7349e52a73 100644
--- a/src/cmd/compile/internal/types/sizeof_test.go
+++ b/src/cmd/compile/internal/types/sizeof_test.go
@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_64bit uintptr     // size on 64bit platforms
 	}{
 		{Sym{}, 44, 72},
-		{Type{}, 60, 104},
+		{Type{}, 64, 112},
 		{Map{}, 20, 40},
 		{Forward{}, 20, 32},
 		{Func{}, 28, 48},
diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index d3c02fc56d..3b0a9706f6 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -182,12 +182,19 @@ type Type struct {
 	flags bitset8
 
 	// For defined (named) generic types, a pointer to the list of type params
-	// (in order) of this type that need to be instantiated. For
-	// fully-instantiated generic types, this is the targs used to instantiate
-	// them (which are used when generating the corresponding instantiated
-	// methods). rparams is only set for named types that are generic or are
-	// fully-instantiated from a generic type, and is otherwise set to nil.
+	// (in order) of this type that need to be instantiated. For instantiated
+	// generic types, this is the targs used to instantiate them. These targs
+	// may be typeparams (for re-instantiated types such as Value[T2]) or
+	// concrete types (for fully instantiated types such as Value[int]).
+	// rparams is only set for named types that are generic or are fully
+	// instantiated from a generic type, and is otherwise set to nil.
+	// TODO(danscales): choose a better name.
 	rparams *[]*Type
+
+	// For an instantiated generic type, the symbol for the base generic type.
+	// This backpointer is useful, because the base type is the type that has
+	// the method bodies.
+	OrigSym *Sym
 }
 
 func (*Type) CanBeAnSSAAux() {}
@@ -213,7 +220,9 @@ func (t *Type) SetBroke(b bool)      { t.flags.set(typeBroke, b) }
 func (t *Type) SetNoalg(b bool)      { t.flags.set(typeNoalg, b) }
 func (t *Type) SetDeferwidth(b bool) { t.flags.set(typeDeferwidth, b) }
 func (t *Type) SetRecur(b bool)      { t.flags.set(typeRecur, b) }
-func (t *Type) SetHasTParam(b bool)  { t.flags.set(typeHasTParam, b) }
+
+// Generic types should never have alg functions.
+func (t *Type) SetHasTParam(b bool) { t.flags.set(typeHasTParam, b); t.flags.set(typeNoalg, b) }
 
 // Kind returns the kind of type t.
 func (t *Type) Kind() Kind { return t.kind }
diff --git a/src/cmd/compile/internal/types2/api_test.go b/src/cmd/compile/internal/types2/api_test.go
index e1020a1219..d82d29cad8 100644
--- a/src/cmd/compile/internal/types2/api_test.go
+++ b/src/cmd/compile/internal/types2/api_test.go
@@ -329,23 +329,23 @@ func TestTypesInfo(t *testing.T) {
 		{brokenPkg + `x5; func _() { var x map[string][...]int; x = map[string][...]int{"": {1,2,3}} }`, `x`, `map[string]invalid type`},
 
 		// parameterized functions
-		{genericPkg + `p0; func f[T any](T); var _ = f[int]`, `f`, `func[T₁ interface{}](T₁)`},
+		{genericPkg + `p0; func f[T any](T); var _ = f[int]`, `f`, `func[generic_p0.T₁ interface{}](generic_p0.T₁)`},
 		{genericPkg + `p1; func f[T any](T); var _ = f[int]`, `f[int]`, `func(int)`},
-		{genericPkg + `p2; func f[T any](T); func _() { f(42) }`, `f`, `func[T₁ interface{}](T₁)`},
+		{genericPkg + `p2; func f[T any](T); func _() { f(42) }`, `f`, `func[generic_p2.T₁ interface{}](generic_p2.T₁)`},
 		{genericPkg + `p3; func f[T any](T); func _() { f(42) }`, `f(42)`, `()`},
 
 		// type parameters
 		{genericPkg + `t0; type t[] int; var _ t`, `t`, `generic_t0.t`}, // t[] is a syntax error that is ignored in this test in favor of t
-		{genericPkg + `t1; type t[P any] int; var _ t[int]`, `t`, `generic_t1.t[P₁ interface{}]`},
-		{genericPkg + `t2; type t[P interface{}] int; var _ t[int]`, `t`, `generic_t2.t[P₁ interface{}]`},
-		{genericPkg + `t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `generic_t3.t[P₁, Q₂ interface{}]`},
-		{brokenPkg + `t4; type t[P, Q interface{ m() }] int; var _ t[int, int]`, `t`, `broken_t4.t[P₁, Q₂ interface{m()}]`},
+		{genericPkg + `t1; type t[P any] int; var _ t[int]`, `t`, `generic_t1.t[generic_t1.P₁ interface{}]`},
+		{genericPkg + `t2; type t[P interface{}] int; var _ t[int]`, `t`, `generic_t2.t[generic_t2.P₁ interface{}]`},
+		{genericPkg + `t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `generic_t3.t[generic_t3.P₁, generic_t3.Q₂ interface{}]`},
+		{brokenPkg + `t4; type t[P, Q interface{ m() }] int; var _ t[int, int]`, `t`, `broken_t4.t[broken_t4.P₁, broken_t4.Q₂ interface{m()}]`},
 
 		// instantiated types must be sanitized
 		{genericPkg + `g0; type t[P any] int; var x struct{ f t[int] }; var _ = x.f`, `x.f`, `generic_g0.t[int]`},
 
 		// issue 45096
-		{genericPkg + `issue45096; func _[T interface{ type int8, int16, int32  }](x T) { _ = x < 0 }`, `0`, `T₁`},
+		{genericPkg + `issue45096; func _[T interface{ type int8, int16, int32  }](x T) { _ = x < 0 }`, `0`, `generic_issue45096.T₁`},
 	}
 
 	for _, test := range tests {
diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index cf119a1b23..55c2f336ce 100644
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -250,6 +250,9 @@ func (s *Signature) RParams() []*TypeName { return s.rparams }
 // SetTParams sets the type parameters of signature s.
 func (s *Signature) SetTParams(tparams []*TypeName) { s.tparams = tparams }
 
+// SetRParams sets the receiver type params of signature s.
+func (s *Signature) SetRParams(rparams []*TypeName) { s.rparams = rparams }
+
 // Params returns the parameters of signature s, or nil.
 func (s *Signature) Params() *Tuple { return s.params }
 
@@ -771,6 +774,12 @@ func (t *TypeParam) Index() int {
 	return t.index
 }
 
+// SetId sets the unique id of a type param. Should only be used for type params
+// in imported generic types.
+func (t *TypeParam) SetId(id uint64) {
+	t.id = id
+}
+
 func (t *TypeParam) Bound() *Interface {
 	iface := asInterface(t.bound)
 	// use the type bound position if we have one
@@ -1002,3 +1011,4 @@ func AsPointer(t Type) *Pointer     { return asPointer(t) }
 func AsNamed(t Type) *Named         { return asNamed(t) }
 func AsSignature(t Type) *Signature { return asSignature(t) }
 func AsInterface(t Type) *Interface { return asInterface(t) }
+func AsTypeParam(t Type) *TypeParam { return asTypeParam(t) }
diff --git a/src/cmd/compile/internal/types2/typestring.go b/src/cmd/compile/internal/types2/typestring.go
index e85cc8ed35..c534b04130 100644
--- a/src/cmd/compile/internal/types2/typestring.go
+++ b/src/cmd/compile/internal/types2/typestring.go
@@ -281,6 +281,13 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
 	case *TypeParam:
 		s := "?"
 		if t.obj != nil {
+			// Optionally write out package for typeparams (like Named).
+			// TODO(danscales): this is required for import/export, so
+			// we maybe need a separate function that won't be changed
+			// for debugging purposes.
+			if t.obj.pkg != nil {
+				writePackage(buf, t.obj.pkg, qf)
+			}
 			s = t.obj.name
 		}
 		buf.WriteString(s + subscript(t.id))