2 files changed, 79 insertions, 15 deletions

diff --git a/src/cmd/compile/internal/syntax/printer.go b/src/cmd/compile/internal/syntax/printer.go
index 9109ce2363..e557f5d924 100644
--- a/src/cmd/compile/internal/syntax/printer.go
+++ b/src/cmd/compile/internal/syntax/printer.go
@@ -481,10 +481,10 @@ func (p *printer) printRawNode(n Node) {
 		if len(n.FieldList) > 0 {
 			if p.linebreaks {
 				p.print(newline, indent)
-				p.printFieldList(n.FieldList, n.TagList)
+				p.printFieldList(n.FieldList, n.TagList, _Semi)
 				p.print(outdent, newline)
 			} else {
-				p.printFieldList(n.FieldList, n.TagList)
+				p.printFieldList(n.FieldList, n.TagList, _Semi)
 			}
 		}
 		p.print(_Rbrace)
@@ -494,20 +494,40 @@ func (p *printer) printRawNode(n Node) {
 		p.printSignature(n)
 
 	case *InterfaceType:
+		// separate type list and method list
+		var types []Expr
+		var methods []*Field
+		for _, f := range n.MethodList {
+			if f.Name != nil && f.Name.Value == "type" {
+				types = append(types, f.Type)
+			} else {
+				// method or embedded interface
+				methods = append(methods, f)
+			}
+		}
+
+		multiLine := len(n.MethodList) > 0 && p.linebreaks
 		p.print(_Interface)
-		if len(n.MethodList) > 0 && p.linebreaks {
+		if multiLine {
 			p.print(blank)
 		}
 		p.print(_Lbrace)
-		if len(n.MethodList) > 0 {
-			if p.linebreaks {
-				p.print(newline, indent)
-				p.printMethodList(n.MethodList)
-				p.print(outdent, newline)
-			} else {
-				p.printMethodList(n.MethodList)
+		if multiLine {
+			p.print(newline, indent)
+		}
+		if len(types) > 0 {
+			p.print(_Type, blank)
+			p.printExprList(types)
+			if len(methods) > 0 {
+				p.print(_Semi, blank)
 			}
 		}
+		if len(methods) > 0 {
+			p.printMethodList(methods)
+		}
+		if multiLine {
+			p.print(outdent, newline)
+		}
 		p.print(_Rbrace)
 
 	case *MapType:
@@ -667,7 +687,13 @@ func (p *printer) printRawNode(n Node) {
 		if n.Group == nil {
 			p.print(_Type, blank)
 		}
-		p.print(n.Name, blank)
+		p.print(n.Name)
+		if n.TParamList != nil {
+			p.print(_Lbrack)
+			p.printFieldList(n.TParamList, nil, _Comma)
+			p.print(_Rbrack)
+		}
+		p.print(blank)
 		if n.Alias {
 			p.print(_Assign, blank)
 		}
@@ -696,6 +722,11 @@ func (p *printer) printRawNode(n Node) {
 			p.print(_Rparen, blank)
 		}
 		p.print(n.Name)
+		if n.TParamList != nil {
+			p.print(_Lbrack)
+			p.printFieldList(n.TParamList, nil, _Comma)
+			p.print(_Rbrack)
+		}
 		p.printSignature(n.Type)
 		if n.Body != nil {
 			p.print(blank, n.Body)
@@ -746,14 +777,14 @@ func (p *printer) printFields(fields []*Field, tags []*BasicLit, i, j int) {
 	}
 }
 
-func (p *printer) printFieldList(fields []*Field, tags []*BasicLit) {
+func (p *printer) printFieldList(fields []*Field, tags []*BasicLit, sep token) {
 	i0 := 0
 	var typ Expr
 	for i, f := range fields {
 		if f.Name == nil || f.Type != typ {
 			if i0 < i {
 				p.printFields(fields, tags, i0, i)
-				p.print(_Semi, newline)
+				p.print(sep, newline)
 				i0 = i
 			}
 			typ = f.Type
diff --git a/src/cmd/compile/internal/syntax/printer_test.go b/src/cmd/compile/internal/syntax/printer_test.go
index bcae815a46..4890327595 100644
--- a/src/cmd/compile/internal/syntax/printer_test.go
+++ b/src/cmd/compile/internal/syntax/printer_test.go
@@ -61,6 +61,21 @@ var stringTests = []string{
 	"package p",
 	"package p; type _ int; type T1 = struct{}; type ( _ *struct{}; T2 = float32 )",
 
+	// generic type declarations
+	"package p; type _[T any] struct{}",
+	"package p; type _[A, B, C interface{m()}] struct{}",
+	"package p; type _[T any, A, B, C interface{m()}, X, Y, Z interface{type int}] struct{}",
+
+	// generic function declarations
+	"package p; func _[T any]()",
+	"package p; func _[A, B, C interface{m()}]()",
+	"package p; func _[T any, A, B, C interface{m()}, X, Y, Z interface{type int}]()",
+
+	// methods with generic receiver types
+	"package p; func (R[T]) _()",
+	"package p; func (*R[A, B, C]) _()",
+	"package p; func (_ *R[A, B, C]) _()",
+
 	// channels
 	"package p; type _ chan chan int",
 	"package p; type _ chan (<-chan int)",
@@ -79,7 +94,7 @@ var stringTests = []string{
 
 func TestPrintString(t *testing.T) {
 	for _, want := range stringTests {
-		ast, err := Parse(nil, strings.NewReader(want), nil, nil, 0)
+		ast, err := Parse(nil, strings.NewReader(want), nil, nil, AllowGenerics)
 		if err != nil {
 			t.Error(err)
 			continue
@@ -116,6 +131,24 @@ var exprTests = [][2]string{
 	{"func(x int) complex128 { return 0 }", "func(x int) complex128 {…}"},
 	{"[]int{1, 2, 3}", "[]int{…}"},
 
+	// type expressions
+	dup("[1 << 10]byte"),
+	dup("[]int"),
+	dup("*int"),
+	dup("struct{x int}"),
+	dup("func()"),
+	dup("func(int, float32) string"),
+	dup("interface{m()}"),
+	dup("interface{m() string; n(x int)}"),
+	dup("interface{type int}"),
+	dup("interface{type int, float64, string}"),
+	dup("interface{type int; m()}"),
+	dup("interface{type int, float64, string; m() string; n(x int)}"),
+	dup("map[string]int"),
+	dup("chan E"),
+	dup("<-chan E"),
+	dup("chan<- E"),
+
 	// non-type expressions
 	dup("(x)"),
 	dup("x.f"),
@@ -172,7 +205,7 @@ var exprTests = [][2]string{
 func TestShortString(t *testing.T) {
 	for _, test := range exprTests {
 		src := "package p; var _ = " + test[0]
-		ast, err := Parse(nil, strings.NewReader(src), nil, nil, 0)
+		ast, err := Parse(nil, strings.NewReader(src), nil, nil, AllowGenerics)
 		if err != nil {
 			t.Errorf("%s: %s", test[0], err)
 			continue