cmd/compile/internal/scanner: report at most one lexical error per number literal

Leave reporting of multiple errors for strings alone for now;
we probably want to see all incorrect escape sequences in
runes/strings independent of other errors.

Fixes #33961.

Change-Id: Id722e95f802687963eec647d1d1841bd6ed17d35
Reviewed-on: https://go-review.googlesource.com/c/go/+/192499
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/syntax/scanner_test.go b/src/cmd/compile/internal/syntax/scanner_test.go
index 3030bfd4c0..717deb9073 100644
--- a/src/cmd/compile/internal/syntax/scanner_test.go
+++ b/src/cmd/compile/internal/syntax/scanner_test.go
@@ -652,3 +652,25 @@ func TestIssue21938(t *testing.T) {
 		t.Errorf("got %s %q; want %s %q", got.tok, got.lit, _Literal, ".5")
 	}
 }
+
+func TestIssue33961(t *testing.T) {
+	literals := `08__ 0b.p 0b_._p 0x.e 0x.p`
+	for _, lit := range strings.Split(literals, " ") {
+		n := 0
+		var got scanner
+		got.init(strings.NewReader(lit), func(_, _ uint, msg string) {
+			// fmt.Printf("%s: %s\n", lit, msg) // uncomment for debugging
+			n++
+		}, 0)
+		got.next()
+
+		if n != 1 {
+			t.Errorf("%q: got %d errors; want 1", lit, n)
+			continue
+		}
+
+		if !got.bad {
+			t.Errorf("%q: got error but bad not set", lit)
+		}
+	}
+}