cmd/compile/internal/syntax: print type parameters and type lists

types2 uses the syntax printer to print expressions (for tracing
or error messages), so we need to (at least) print type lists in
interfaces.

While at it, also implement the printing of type parameter lists.

Fixes #44766.

Change-Id: I36a4a7152d9bef7251af264b5c7890aca88d8dc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/298549
Trust: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: griesemer

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

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