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go/printer: fix invalid output for empty decls

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The current output for empty declarations such as var, const, import
results in "var", "const", "import" respectively. These are not valid
and the parser will promptly reject them as invalid syntax.

This CL updates this behavior by adding "()" to the output of empty
decls so the syntax becomes valid, e.g "var ()" instead of "var".

Fixes #63566

Change-Id: I571b182d9ccf71b159360c8de003ad55d0ff3443
GitHub-Last-Rev: 2720419e364938e9962be71d0e6ed51375fec404
GitHub-Pull-Request: golang/go#63593
Reviewed-on: https://go-review.googlesource.com/c/go/+/535995
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Mauri de Souza Meneguzzo <mauri870@gmail.com>
This commit is contained in:
Mauri de Souza Meneguzzo 2023-10-17 18:36:31 +00:00 committed by Gopher Robot
parent 860c2557ab
commit ff7986d670
2 changed files with 16 additions and 1 deletions
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2
src/go/printer/nodes.go
View File

@ -1739,7 +1739,7 @@ func (p *printer) genDecl(d *ast.GenDecl) {
p.setPos(d.Pos())
p.print(d.Tok, blank)
if d.Lparen.IsValid() || len(d.Specs) > 1 {
if d.Lparen.IsValid() || len(d.Specs) != 1 {
// group of parenthesized declarations
p.setPos(d.Lparen)
p.print(token.LPAREN)

15
src/go/printer/printer_test.go
View File

@ -848,3 +848,18 @@ func TestSourcePosNewline(t *testing.T) {
t.Errorf("unexpected Fprint output:\n%s", buf.Bytes())
}
}
// TestEmptyDecl tests that empty decls for const, var, import are printed with
// valid syntax e.g "var ()" instead of just "var", which is invalid and cannot
// be parsed.
func TestEmptyDecl(t *testing.T) { // issue 63566
for _, tok := range []token.Token{token.IMPORT, token.CONST, token.TYPE, token.VAR} {
var buf bytes.Buffer
Fprint(&buf, token.NewFileSet(), &ast.GenDecl{Tok: tok})
got := buf.String()
want := tok.String() + " ()"
if got != want {
t.Errorf("got %q, want %q", got, want)
}
}
}