interp: improve handling of generic types

When generating a new type, the parameter type was not correctly duplicated in the new AST. This is fixed by making copyNode recursive if needed. The out of order processing of generic types has also been fixed.

Fixes #1488

_test/gen11.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/netip"
+)
+
+type Slice[T any] struct {
+	x []T
+}
+
+type IPPrefixSlice struct {
+	x Slice[netip.Prefix]
+}
+
+func (v Slice[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.x) }
+
+// MarshalJSON implements json.Marshaler.
+func (v IPPrefixSlice) MarshalJSON() ([]byte, error) {
+	return v.x.MarshalJSON()
+}
+
+func main() {
+	t := IPPrefixSlice{}
+	fmt.Println(t)
+	b, e := t.MarshalJSON()
+	fmt.Println(string(b), e)
+}
+
+// Output:
+// {{[]}}
+// null <nil>

_test/gen12.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+)
+
+func MapOf[K comparable, V any](m map[K]V) Map[K, V] {
+	return Map[K, V]{m}
+}
+
+type Map[K comparable, V any] struct {
+	ж map[K]V
+}
+
+func (v MapView) Int() Map[string, int] { return MapOf(v.ж.Int) }
+
+type VMap struct {
+	Int map[string]int
+}
+
+type MapView struct {
+	ж *VMap
+}
+
+func main() {
+	mv := MapView{&VMap{}}
+	fmt.Println(mv.ж)
+}
+
+// Output:
+// &{map[]}

_test/gen13.go

@@ -0,0 +1,18 @@
+package main
+
+type Map[K comparable, V any] struct {
+	ж map[K]V
+}
+
+func (m Map[K, V]) Has(k K) bool {
+	_, ok := m.ж[k]
+	return ok
+}
+
+func main() {
+	m := Map[string, float64]{}
+	println(m.Has("test"))
+}
+
+// Output:
+// false

_test/issue-1460.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
+	"net/netip"
 	"reflect"
 )
 
@@ -17,6 +18,10 @@ func unmarshalJSON[T any](b []byte, x *[]T) error {
 	return json.Unmarshal(b, x)
 }
 
+func SliceOfViews[T ViewCloner[T, V], V StructView[T]](x []T) SliceView[T, V] {
+	return SliceView[T, V]{x}
+}
+
 type StructView[T any] interface {
 	Valid() bool
 	AsStruct() T
@@ -31,10 +36,6 @@ type ViewCloner[T any, V StructView[T]] interface {
 	Clone() T
 }
 
-func SliceOfViews[T ViewCloner[T, V], V StructView[T]](x []T) SliceView[T, V] {
-	return SliceView[T, V]{x}
-}
-
 func (v SliceView[T, V]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
 
 func (v *SliceView[T, V]) UnmarshalJSON(b []byte) error { return unmarshalJSON(b, &v.ж) }
@@ -51,6 +52,10 @@ func SliceOf[T any](x []T) Slice[T] {
 	return Slice[T]{x}
 }
 
+type IPPrefixSlice struct {
+	ж Slice[netip.Prefix]
+}
+
 type viewStruct struct {
 	Int        int
 	Strings    Slice[string]

_test/issue-1488.go

@@ -0,0 +1,23 @@
+package main
+
+import "fmt"
+
+type vector interface {
+	[]int | [3]int
+}
+
+func sum[V vector](v V) (out int) {
+	for i := 0; i < len(v); i++ {
+		out += v[i]
+	}
+	return
+}
+
+func main() {
+	va := [3]int{1, 2, 3}
+	vs := []int{1, 2, 3}
+	fmt.Println(sum[[3]int](va), sum[[]int](vs))
+}
+
+// Output:
+// 6 6

_test/p6.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/traefik/yaegi/_test/p6"
+)
+
+func main() {
+	t := p6.IPPrefixSlice{}
+	fmt.Println(t)
+	b, e := t.MarshalJSON()
+	fmt.Println(string(b), e)
+}

_test/p6/p6.go

@@ -0,0 +1,21 @@
+package p6
+
+import (
+	"encoding/json"
+	"net/netip"
+)
+
+type Slice[T any] struct {
+	x []T
+}
+
+type IPPrefixSlice struct {
+	x Slice[netip.Prefix]
+}
+
+func (v Slice[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.x) }
+
+// MarshalJSON implements json.Marshaler.
+func (v IPPrefixSlice) MarshalJSON() ([]byte, error) {
+	return v.x.MarshalJSON()
+}

interp/cfg.go

@@ -322,8 +322,60 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					}
 				}
 				if n.typ == nil {
-					err = n.cfgErrorf("undefined type")
-					return false
+					// A nil type indicates either an error or a generic type.
+					// A child indexExpr or indexListExpr is used for type parameters,
+					// it indicates an instanciated generic.
+					if n.child[0].kind != indexExpr && n.child[0].kind != indexListExpr {
+						err = n.cfgErrorf("undefined type")
+						return false
+					}
+					t0, err1 := nodeType(interp, sc, n.child[0].child[0])
+					if err1 != nil {
+						return false
+					}
+					if t0.cat != genericT {
+						err = n.cfgErrorf("undefined type")
+						return false
+					}
+					// We have a composite literal of generic type, instantiate it.
+					lt := []*itype{}
+					for _, n1 := range n.child[0].child[1:] {
+						t1, err1 := nodeType(interp, sc, n1)
+						if err1 != nil {
+							return false
+						}
+						lt = append(lt, t1)
+					}
+					var g *node
+					g, _, err = genAST(sc, t0.node.anc, lt)
+					if err != nil {
+						return false
+					}
+					n.child[0] = g.lastChild()
+					n.typ, err = nodeType(interp, sc, n.child[0])
+					if err != nil {
+						return false
+					}
+					// Generate methods if any.
+					for _, nod := range t0.method {
+						gm, _, err2 := genAST(nod.scope, nod, lt)
+						if err2 != nil {
+							err = err2
+							return false
+						}
+						gm.typ, err = nodeType(interp, nod.scope, gm.child[2])
+						if err != nil {
+							return false
+						}
+						if _, err = interp.cfg(gm, sc, sc.pkgID, sc.pkgName); err != nil {
+							return false
+						}
+						if err = genRun(gm); err != nil {
+							return false
+						}
+						n.typ.addMethod(gm)
+					}
+					n.nleft = 1 // Indictate the type of composite literal.
 				}
 			}
 
@@ -439,6 +491,19 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				if typ, err = nodeType(interp, sc, recvTypeNode); err != nil {
 					return false
 				}
+				if typ.cat == nilT {
+					// This may happen when instantiating generic methods.
+					s2, _, ok := sc.lookup(typ.id())
+					if !ok {
+						err = n.cfgErrorf("type not found: %s", typ.id())
+						break
+					}
+					typ = s2.typ
+					if typ.cat == nilT {
+						err = n.cfgErrorf("nil type: %s", typ.id())
+						break
+					}
+				}
 				recvTypeNode.typ = typ
 				n.child[2].typ.recv = typ
 				n.typ.recv = typ
@@ -871,16 +936,18 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					n.typ = t
 					return
 				}
-				g, err := genAST(sc, t.node.anc, []*node{c1})
+				g, found, err := genAST(sc, t.node.anc, []*itype{c1.typ})
 				if err != nil {
 					return
 				}
-				if _, err = interp.cfg(g, nil, importPath, pkgName); err != nil {
-					return
-				}
-				// Generate closures for function body.
-				if err = genRun(g.child[3]); err != nil {
-					return
+				if !found {
+					if _, err = interp.cfg(g, t.node.anc.scope, importPath, pkgName); err != nil {
+						return
+					}
+					// Generate closures for function body.
+					if err = genRun(g.child[3]); err != nil {
+						return
+					}
 				}
 				// Replace generic func node by instantiated one.
 				n.anc.child[childPos(n)] = g
@@ -1030,17 +1097,23 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			case c0.kind == indexListExpr:
 				// Instantiate a generic function then call it.
 				fun := c0.child[0].sym.node
-				g, err := genAST(sc, fun, c0.child[1:])
+				lt := []*itype{}
+				for _, c := range c0.child[1:] {
+					lt = append(lt, c.typ)
+				}
+				g, found, err := genAST(sc, fun, lt)
 				if err != nil {
 					return
 				}
-				_, err = interp.cfg(g, nil, importPath, pkgName)
-				if err != nil {
-					return
-				}
-				err = genRun(g.child[3]) // Generate closures for function body.
-				if err != nil {
-					return
+				if !found {
+					_, err = interp.cfg(g, fun.scope, importPath, pkgName)
+					if err != nil {
+						return
+					}
+					err = genRun(g.child[3]) // Generate closures for function body.
+					if err != nil {
+						return
+					}
 				}
 				n.child[0] = g
 				c0 = n.child[0]
@@ -1212,23 +1285,26 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				if isGeneric(c0.typ) {
 					fun := c0.typ.node.anc
 					var g *node
-					var types []*node
+					var types []*itype
+					var found bool
 
 					// Infer type parameter from function call arguments.
 					if types, err = inferTypesFromCall(sc, fun, n.child[1:]); err != nil {
 						break
 					}
 					// Generate an instantiated AST from the generic function one.
-					if g, err = genAST(sc, fun, types); err != nil {
+					if g, found, err = genAST(sc, fun, types); err != nil {
 						break
 					}
-					// Compile the generated function AST, so it becomes part of the scope.
-					if _, err = interp.cfg(g, nil, importPath, pkgName); err != nil {
-						break
-					}
-					// AST compilation part 2: Generate closures for function body.
-					if err = genRun(g.child[3]); err != nil {
-						break
+					if !found {
+						// Compile the generated function AST, so it becomes part of the scope.
+						if _, err = interp.cfg(g, fun.scope, importPath, pkgName); err != nil {
+							break
+						}
+						// AST compilation part 2: Generate closures for function body.
+						if err = genRun(g.child[3]); err != nil {
+							break
+						}
 					}
 					n.child[0] = g
 					c0 = n.child[0]
@@ -1487,6 +1563,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 
 			sym, level, found := sc.lookup(n.ident)
 			if !found {
+				if n.typ != nil {
+					// Node is a generic instance with an already populated type.
+					break
+				}
 				// retry with the filename, in case ident is a package name.
 				sym, level, found = sc.lookup(filepath.Join(n.ident, baseName))
 				if !found {
@@ -1916,7 +1996,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					err = n.cfgErrorf("undefined selector: %s", n.child[1].ident)
 				}
 			}
-			if err == nil && n.findex != -1 {
+			if err == nil && n.findex != -1 && n.typ.cat != genericT {
 				n.findex = sc.add(n.typ)
 			}
 
@@ -2375,11 +2455,13 @@ func (n *node) cfgErrorf(format string, a ...interface{}) *cfgError {
 
 func genRun(nod *node) error {
 	var err error
+	seen := map[*node]bool{}
 
 	nod.Walk(func(n *node) bool {
-		if err != nil {
+		if err != nil || seen[n] {
 			return false
 		}
+		seen[n] = true
 		switch n.kind {
 		case funcType:
 			if len(n.anc.child) == 4 {

interp/generic.go

@@ -5,8 +5,11 @@ import (
 	"sync/atomic"
 )
 
+// adot produces an AST dot(1) directed acyclic graph for the given node. For debugging only.
+// func (n *node) adot() { n.astDot(dotWriter(n.interp.dotCmd), n.ident) }
+
 // genAST returns a new AST where generic types are replaced by instantiated types.
-func genAST(sc *scope, root *node, types []*node) (*node, error) {
+func genAST(sc *scope, root *node, types []*itype) (*node, bool, error) {
 	typeParam := map[string]*node{}
 	pindex := 0
 	tname := ""
@@ -14,9 +17,20 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 	recvrPtr := false
 	fixNodes := []*node{}
 	var gtree func(*node, *node) (*node, error)
+	sname := root.child[0].ident + "["
+	if root.kind == funcDecl {
+		sname = root.child[1].ident + "["
+	}
+
+	// Input type parameters must be resolved prior AST generation, as compilation
+	// of generated AST may occur in a different scope.
+	for _, t := range types {
+		sname += t.id() + ","
+	}
+	sname = strings.TrimSuffix(sname, ",") + "]"
 
 	gtree = func(n, anc *node) (*node, error) {
-		nod := copyNode(n, anc)
+		nod := copyNode(n, anc, false)
 		switch n.kind {
 		case funcDecl, funcType:
 			nod.val = nod
@@ -27,7 +41,8 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 			if !ok {
 				break
 			}
-			nod = copyNode(nt, anc)
+			nod = copyNode(nt, anc, true)
+			nod.typ = nt.typ
 
 		case indexExpr:
 			// Catch a possible recursive generic type definition
@@ -37,7 +52,7 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 			if root.child[0].ident != n.child[0].ident {
 				break
 			}
-			nod := copyNode(n.child[0], anc)
+			nod := copyNode(n.child[0], anc, false)
 			fixNodes = append(fixNodes, nod)
 			return nod, nil
 
@@ -51,10 +66,16 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 						if pindex >= len(types) {
 							return nil, cc.cfgErrorf("undefined type for %s", cc.ident)
 						}
-						if err := checkConstraint(sc, types[pindex], c.child[l]); err != nil {
+						t, err := nodeType(c.interp, sc, c.child[l])
+						if err != nil {
 							return nil, err
 						}
-						typeParam[cc.ident] = types[pindex]
+						if err := checkConstraint(types[pindex], t); err != nil {
+							return nil, err
+						}
+						typeParam[cc.ident] = copyNode(cc, cc.anc, false)
+						typeParam[cc.ident].ident = types[pindex].id()
+						typeParam[cc.ident].typ = types[pindex]
 						pindex++
 					}
 				}
@@ -65,9 +86,9 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 			// Node is the receiver of a generic method.
 			if root.kind == funcDecl && n.anc == root && childPos(n) == 0 && len(n.child) > 0 {
 				rtn := n.child[0].child[1]
-				if rtn.kind == indexExpr || (rtn.kind == starExpr && rtn.child[0].kind == indexExpr) {
-					// Method receiver is a generic type.
-					if rtn.kind == starExpr && rtn.child[0].kind == indexExpr {
+				// Method receiver is a generic type if it takes some type parameters.
+				if rtn.kind == indexExpr || rtn.kind == indexListExpr || (rtn.kind == starExpr && (rtn.child[0].kind == indexExpr || rtn.child[0].kind == indexListExpr)) {
+					if rtn.kind == starExpr {
 						// Method receiver is a pointer on a generic type.
 						rtn = rtn.child[0]
 						recvrPtr = true
@@ -77,11 +98,10 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 						if pindex >= len(types) {
 							return nil, cc.cfgErrorf("undefined type for %s", cc.ident)
 						}
-						it, err := nodeType(n.interp, sc, types[pindex])
-						if err != nil {
-							return nil, err
-						}
-						typeParam[cc.ident] = types[pindex]
+						it := types[pindex]
+						typeParam[cc.ident] = copyNode(cc, cc.anc, false)
+						typeParam[cc.ident].ident = it.id()
+						typeParam[cc.ident].typ = it
 						rtname += it.id() + ","
 						pindex++
 					}
@@ -99,14 +119,17 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 						if pindex >= len(types) {
 							return nil, cc.cfgErrorf("undefined type for %s", cc.ident)
 						}
-						it, err := nodeType(n.interp, sc, types[pindex])
+						it := types[pindex]
+						t, err := nodeType(c.interp, sc, c.child[l])
 						if err != nil {
 							return nil, err
 						}
-						if err := checkConstraint(sc, types[pindex], c.child[l]); err != nil {
+						if err := checkConstraint(types[pindex], t); err != nil {
 							return nil, err
 						}
-						typeParam[cc.ident] = types[pindex]
+						typeParam[cc.ident] = copyNode(cc, cc.anc, false)
+						typeParam[cc.ident].ident = it.id()
+						typeParam[cc.ident].typ = it
 						tname += it.id() + ","
 						pindex++
 					}
@@ -115,6 +138,7 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 				return nod, nil
 			}
 		}
+
 		for _, c := range n.child {
 			gn, err := gtree(c, nod)
 			if err != nil {
@@ -125,10 +149,16 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 		return nod, nil
 	}
 
+	if nod, found := root.interp.generic[sname]; found {
+		return nod, true, nil
+	}
+
 	r, err := gtree(root, root.anc)
 	if err != nil {
-		return nil, err
+		return nil, false, err
 	}
+	root.interp.generic[sname] = r
+	r.param = append(r.param, types...)
 	if tname != "" {
 		for _, nod := range fixNodes {
 			nod.ident = tname
@@ -145,11 +175,11 @@ func genAST(sc *scope, root *node, types []*node) (*node, error) {
 		nod.ident = rtname
 		nod.child = nil
 	}
-	// r.astDot(dotWriter(root.interp.dotCmd), root.child[1].ident) // Used for debugging only.
-	return r, nil
+	// r.adot() // Used for debugging only.
+	return r, false, nil
 }
 
-func copyNode(n, anc *node) *node {
+func copyNode(n, anc *node, recursive bool) *node {
 	var i interface{}
 	nindex := atomic.AddInt64(&n.interp.nindex, 1)
 	nod := &node{
@@ -170,25 +200,30 @@ func copyNode(n, anc *node) *node {
 		meta:   n.meta,
 	}
 	nod.start = nod
+	if recursive {
+		for _, c := range n.child {
+			nod.child = append(nod.child, copyNode(c, nod, true))
+		}
+	}
 	return nod
 }
 
-func inferTypesFromCall(sc *scope, fun *node, args []*node) ([]*node, error) {
+func inferTypesFromCall(sc *scope, fun *node, args []*node) ([]*itype, error) {
 	ftn := fun.typ.node
 	// Fill the map of parameter types, indexed by type param ident.
-	types := map[string]*itype{}
+	paramTypes := map[string]*itype{}
 	for _, c := range ftn.child[0].child {
 		typ, err := nodeType(fun.interp, sc, c.lastChild())
 		if err != nil {
 			return nil, err
 		}
 		for _, cc := range c.child[:len(c.child)-1] {
-			types[cc.ident] = typ
+			paramTypes[cc.ident] = typ
 		}
 	}
 
-	var inferTypes func(*itype, *itype) ([]*node, error)
-	inferTypes = func(param, input *itype) ([]*node, error) {
+	var inferTypes func(*itype, *itype) ([]*itype, error)
+	inferTypes = func(param, input *itype) ([]*itype, error) {
 		switch param.cat {
 		case chanT, ptrT, sliceT:
 			return inferTypes(param.val, input.val)
@@ -205,65 +240,68 @@ func inferTypesFromCall(sc *scope, fun *node, args []*node) ([]*node, error) {
 			return append(k, v...), nil
 
 		case structT:
-			nods := []*node{}
+			lt := []*itype{}
 			for i, f := range param.field {
 				nl, err := inferTypes(f.typ, input.field[i].typ)
 				if err != nil {
 					return nil, err
 				}
-				nods = append(nods, nl...)
+				lt = append(lt, nl...)
 			}
-			return nods, nil
+			return lt, nil
 
 		case funcT:
-			nods := []*node{}
+			lt := []*itype{}
 			for i, t := range param.arg {
+				if i >= len(input.arg) {
+					break
+				}
 				nl, err := inferTypes(t, input.arg[i])
 				if err != nil {
 					return nil, err
 				}
-				nods = append(nods, nl...)
+				lt = append(lt, nl...)
 			}
 			for i, t := range param.ret {
+				if i >= len(input.ret) {
+					break
+				}
 				nl, err := inferTypes(t, input.ret[i])
 				if err != nil {
 					return nil, err
 				}
-				nods = append(nods, nl...)
+				lt = append(lt, nl...)
+			}
+			return lt, nil
+
+		case nilT:
+			if paramTypes[param.name] != nil {
+				return []*itype{input}, nil
 			}
-			return nods, nil
 
 		case genericT:
-			return []*node{input.node}, nil
+			return []*itype{input}, nil
 		}
 		return nil, nil
 	}
 
-	nodes := []*node{}
+	types := []*itype{}
 	for i, c := range ftn.child[1].child {
 		typ, err := nodeType(fun.interp, sc, c.lastChild())
 		if err != nil {
 			return nil, err
 		}
-		nods, err := inferTypes(typ, args[i].typ)
+		lt, err := inferTypes(typ, args[i].typ)
 		if err != nil {
 			return nil, err
 		}
-		nodes = append(nodes, nods...)
+		types = append(types, lt...)
 	}
 
-	return nodes, nil
+	return types, nil
 }
 
-func checkConstraint(sc *scope, input, constraint *node) error {
-	ct, err := nodeType(constraint.interp, sc, constraint)
-	if err != nil {
-		return err
-	}
-	it, err := nodeType(input.interp, sc, input)
-	if err != nil {
-		return err
-	}
+func checkConstraint(it, ct *itype) error {
 	if len(ct.constraint) == 0 && len(ct.ulconstraint) == 0 {
 		return nil
 	}
@@ -277,5 +315,5 @@ func checkConstraint(sc *scope, input, constraint *node) error {
 			return nil
 		}
 	}
-	return input.cfgErrorf("%s does not implement %s", input.typ.id(), ct.id())
+	return it.node.cfgErrorf("%s does not implement %s", it.id(), ct.id())
 }

interp/gta.go

@@ -21,6 +21,9 @@ func (interp *Interpreter) gta(root *node, rpath, importPath, pkgName string) ([
 		if err != nil {
 			return false
 		}
+		if n.scope == nil {
+			n.scope = sc
+		}
 		switch n.kind {
 		case constDecl:
 			// Early parse of constDecl subtree, to compute all constant
@@ -166,7 +169,7 @@ func (interp *Interpreter) gta(root *node, rpath, importPath, pkgName string) ([
 							typName = c.child[0].ident
 							genericMethod = true
 						}
-					case indexExpr:
+					case indexExpr, indexListExpr:
 						genericMethod = true
 					}
 				}
@@ -189,6 +192,14 @@ func (interp *Interpreter) gta(root *node, rpath, importPath, pkgName string) ([
 				}
 				rcvrtype.addMethod(n)
 				rtn.typ = rcvrtype
+				if rcvrtype.cat == genericT {
+					// generate methods for already instantiated receivers
+					for _, it := range rcvrtype.instance {
+						if err = genMethod(interp, sc, it, n, it.node.anc.param); err != nil {
+							return false
+						}
+					}
+				}
 			case ident == "init":
 				// init functions do not get declared as per the Go spec.
 			default:

interp/interp.go

@@ -28,6 +28,7 @@ type node struct {
 	debug  *nodeDebugData // debug info
 	child  []*node        // child subtrees (AST)
 	anc    *node          // ancestor (AST)
+	param  []*itype       // generic parameter nodes (AST)
 	start  *node          // entry point in subtree (CFG)
 	tnext  *node          // true branch successor (CFG)
 	fnext  *node          // false branch successor (CFG)
@@ -215,6 +216,7 @@ type Interpreter struct {
 	pkgNames map[string]string // package names, indexed by import path
 	done     chan struct{}     // for cancellation of channel operations
 	roots    []*node
+	generic  map[string]*node
 
 	hooks *hooks // symbol hooks
 
@@ -335,6 +337,7 @@ func New(options Options) *Interpreter {
 		pkgNames: map[string]string{},
 		rdir:     map[string]bool{},
 		hooks:    &hooks{},
+		generic:  map[string]*node{},
 	}
 
 	if i.opt.stdin = options.Stdin; i.opt.stdin == nil {

interp/type.go

@@ -126,6 +126,7 @@ type itype struct {
 	method       []*node       // Associated methods or nil
 	constraint   []*itype      // For interfaceT: list of types part of interface set
 	ulconstraint []*itype      // For interfaceT: list of underlying types part of interface set
+	instance     []*itype      // For genericT: list of instantiated types
 	name         string        // name of type within its package for a defined type
 	path         string        // for a defined type, the package import path
 	length       int           // length of array if ArrayT
@@ -786,6 +787,11 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		} else {
 			t = sym.typ
 		}
+		if t == nil {
+			if t, err = nodeType2(interp, sc, sym.node, seen); err != nil {
+				return nil, err
+			}
+		}
 		if t.incomplete && t.cat == linkedT && t.val != nil && t.val.cat != nilT {
 			t.incomplete = false
 		}
@@ -807,7 +813,11 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 			return nil, err
 		}
 		if lt.incomplete {
-			t.incomplete = true
+			if t == nil {
+				t = lt
+			} else {
+				t.incomplete = true
+			}
 			break
 		}
 		switch lt.cat {
@@ -828,7 +838,7 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 				break
 			}
 			// A generic type is being instantiated. Generate it.
-			t, err = genType(interp, sc, name, lt, []*node{t1.node}, seen)
+			t, err = genType(interp, sc, name, lt, []*itype{t1}, seen)
 			if err != nil {
 				return nil, err
 			}
@@ -840,6 +850,15 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		if lt, err = nodeType2(interp, sc, n.child[0], seen); err != nil {
 			return nil, err
 		}
+		if lt.incomplete {
+			if t == nil {
+				t = lt
+			} else {
+				t.incomplete = true
+			}
+			break
+		}
+
 		// Index list expressions can be used only in context of generic types.
 		if lt.cat != genericT {
 			err = n.cfgErrorf("not a generic type: %s", lt.id())
@@ -847,7 +866,7 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		}
 		name := lt.id() + "["
 		out := false
-		tnodes := []*node{}
+		types := []*itype{}
 		for _, c := range n.child[1:] {
 			t1, err := nodeType2(interp, sc, c, seen)
 			if err != nil {
@@ -858,19 +877,19 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 				out = true
 				break
 			}
-			tnodes = append(tnodes, t1.node)
+			types = append(types, t1)
 			name += t1.id() + ","
 		}
 		if out {
 			break
 		}
-		name += "]"
+		name = strings.TrimSuffix(name, ",") + "]"
 		if sym, _, found := sc.lookup(name); found {
 			t = sym.typ
 			break
 		}
 		// A generic type is being instantiated. Generate it.
-		t, err = genType(interp, sc, name, lt, tnodes, seen)
+		t, err = genType(interp, sc, name, lt, types, seen)
 
 	case interfaceType:
 		if sname := typeName(n); sname != "" {
@@ -1016,7 +1035,7 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		sname := structName(n)
 		if sname != "" {
 			sym, _, found = sc.lookup(sname)
-			if found && sym.kind == typeSym {
+			if found && sym.kind == typeSym && sym.typ != nil {
 				t = structOf(sym.typ, sym.typ.field, withNode(n), withScope(sc))
 			} else {
 				t = structOf(nil, nil, withNode(n), withScope(sc))
@@ -1062,6 +1081,9 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		t = structOf(t, fields, withNode(n), withScope(sc))
 		t.incomplete = incomplete
 		if sname != "" {
+			if sc.sym[sname] == nil {
+				sc.sym[sname] = &symbol{index: -1, kind: typeSym, node: n}
+			}
 			sc.sym[sname].typ = t
 		}
 
@@ -1094,9 +1116,9 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 	return t, err
 }
 
-func genType(interp *Interpreter, sc *scope, name string, lt *itype, tnodes, seen []*node) (t *itype, err error) {
+func genType(interp *Interpreter, sc *scope, name string, lt *itype, types []*itype, seen []*node) (t *itype, err error) {
 	// A generic type is being instantiated. Generate it.
-	g, err := genAST(sc, lt.node.anc, tnodes)
+	g, _, err := genAST(sc, lt.node.anc, types)
 	if err != nil {
 		return nil, err
 	}
@@ -1104,39 +1126,48 @@ func genType(interp *Interpreter, sc *scope, name string, lt *itype, tnodes, see
 	if err != nil {
 		return nil, err
 	}
+	lt.instance = append(lt.instance, t)
+	// Add generated symbol in the scope of generic source and user.
 	sc.sym[name] = &symbol{index: -1, kind: typeSym, typ: t, node: g}
-
-	// Instantiate type methods (if any).
-	var pt *itype
-	if len(lt.method) > 0 {
-		pt = ptrOf(t, withNode(g), withScope(sc))
+	if lt.scope.sym[name] == nil {
+		lt.scope.sym[name] = sc.sym[name]
 	}
+
 	for _, nod := range lt.method {
-		gm, err := genAST(sc, nod, tnodes)
-		if err != nil {
-			return nil, err
-		}
-		if gm.typ, err = nodeType(interp, sc, gm.child[2]); err != nil {
-			return nil, err
-		}
-		t.addMethod(gm)
-		if rtn := gm.child[0].child[0].lastChild(); rtn.kind == starExpr {
-			// The receiver is a pointer on a generic type.
-			pt.addMethod(gm)
-			rtn.typ = pt
-		}
-		// Compile method CFG.
-		if _, err = interp.cfg(gm, sc, sc.pkgID, sc.pkgName); err != nil {
-			return nil, err
-		}
-		// Generate closures for function body.
-		if err = genRun(gm); err != nil {
+		if err := genMethod(interp, sc, t, nod, types); err != nil {
 			return nil, err
 		}
 	}
 	return t, err
 }
 
+func genMethod(interp *Interpreter, sc *scope, t *itype, nod *node, types []*itype) error {
+	gm, _, err := genAST(sc, nod, types)
+	if err != nil {
+		return err
+	}
+	if gm.typ, err = nodeType(interp, sc, gm.child[2]); err != nil {
+		return err
+	}
+	t.addMethod(gm)
+
+	// If the receiver is a pointer to a generic type, generate also the pointer type.
+	if rtn := gm.child[0].child[0].lastChild(); rtn != nil && rtn.kind == starExpr {
+		pt := ptrOf(t, withNode(t.node), withScope(sc))
+		pt.addMethod(gm)
+		rtn.typ = pt
+	}
+
+	// Compile the method AST in the scope of the generic type.
+	scop := nod.typ.scope
+	if _, err = interp.cfg(gm, scop, scop.pkgID, scop.pkgName); err != nil {
+		return err
+	}
+
+	// Generate closures for function body.
+	return genRun(gm)
+}
+
 // findPackageType searches the top level scope for a package type.
 func findPackageType(interp *Interpreter, sc *scope, n *node) *itype {
 	// Find the root scope, the package symbols will exist there.