cmd/compile/internal/gc: add dropped line correction again

The line correction when reporting a missing package clause
was removed before since it wasn't clear that it was needed.
Added it again because of issue 13267.

No explicit test case has been added to test/fixedbugs because
it would require a file that contains a single byte and such a
file doesn't fit the existing test harness. Instead documented
the problematic line in the parser for future reference.

Fixes #13267.

Change-Id: I590fe8f358042aab73acf16c2ed9567872b174f4
Reviewed-on: https://go-review.googlesource.com/16975
Reviewed-by: Chris Manghane <cmang@golang.org>

diff --git a/src/cmd/compile/internal/gc/parser.go b/src/cmd/compile/internal/gc/parser.go
index 1d24b271e078947f0b5fd6a256d2fb62b854f33b..4eb4339a26c7e4c1945c4c22aba815f62ae0732a 100644 (file)
--- a/src/cmd/compile/internal/gc/parser.go
+++ b/src/cmd/compile/internal/gc/parser.go
@@ -307,6 +307,7 @@ func (p *parser) package_() {
                mkpackage(p.sym().Name)
                p.want(';')
        } else {
+               prevlineno = lineno // see issue #13267
                p.syntax_error("package statement must be first")
                errorexit()
        }