[dev.typealias] cmd/compile: recognize type aliases but complain for now (not yet supported)

Added test file.

For #18130.

Change-Id: Ifcfd7cd1acf9dd6a2f4f3d85979d232bb6b8c6b1
Reviewed-on: https://go-review.googlesource.com/34988
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

4 files changed, 25 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index fadba84bce..34524e5c09 100644
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -74,6 +74,7 @@ type (
 	// Name Type
 	TypeDecl struct {
 		Name   *Name
+		Alias  bool
 		Type   Expr
 		Group  *Group // nil means not part of a group
 		Pragma Pragma
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 121dfb75e5..1185507238 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -325,7 +325,7 @@ func (p *parser) constDecl(group *Group) Decl {
 	return d
 }
 
-// TypeSpec = identifier Type .
+// TypeSpec = identifier [ "=" ] Type .
 func (p *parser) typeDecl(group *Group) Decl {
 	if trace {
 		defer p.trace("typeDecl")()
@@ -335,6 +335,7 @@ func (p *parser) typeDecl(group *Group) Decl {
 	d.init(p)
 
 	d.Name = p.name()
+	d.Alias = p.got(_Assign)
 	d.Type = p.tryType()
 	if d.Type == nil {
 		p.syntax_error("in type declaration")
diff --git a/src/cmd/compile/internal/syntax/printer.go b/src/cmd/compile/internal/syntax/printer.go
index 0cacf1e5d4..43876a25c2 100644
--- a/src/cmd/compile/internal/syntax/printer.go
+++ b/src/cmd/compile/internal/syntax/printer.go
@@ -619,7 +619,11 @@ func (p *printer) printRawNode(n Node) {
 		if n.Group == nil {
 			p.print(_Type, blank)
 		}
-		p.print(n.Name, blank, n.Type)
+		p.print(n.Name, blank)
+		if n.Alias {
+			p.print(_Assign, blank)
+		}
+		p.print(n.Type)
 
 	case *VarDecl:
 		if n.Group == nil {
diff --git a/src/cmd/compile/internal/syntax/printer_test.go b/src/cmd/compile/internal/syntax/printer_test.go
index 5c0fc776a1..a9969e610a 100644
--- a/src/cmd/compile/internal/syntax/printer_test.go
+++ b/src/cmd/compile/internal/syntax/printer_test.go
@@ -22,3 +22,20 @@ func TestPrint(t *testing.T) {
 	Fprint(os.Stdout, ast, true)
 	fmt.Println()
 }
+
+func TestPrintString(t *testing.T) {
+	for _, want := range []string{
+		"package p",
+		"package p; type _ = int; type T1 = struct{}; type ( _ = *struct{}; T2 = float32 )",
+		// TODO(gri) expand
+	} {
+		ast, err := ParseBytes([]byte(want), nil, nil, 0)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		if got := String(ast); got != want {
+			t.Errorf("%q: got %q", want, got)
+		}
+	}
+}