toke.c: Avoid extra sv_setpv for foo <newline> =>

When parsing something like

    time
       =>

if there is a global override, the parser transforms ‘time’ into
‘CORE::GLOBAL::time’ before it looks at the next line to see if there
is a fat arrow.

If it finds a fat arrow, it has to set the name back to ‘time’.

After finding a fat arrow on the line following a bareword, it was
setting the name to what appears in the program source, even when
there was no global override.  We can skip that most of the time.

All that I said about global overrides applies to ‘our’ subs, too.
‘foo’ gets transformed into ‘ThatPackage::foo’ and needs to be changed
back.  I added a test, to make sure that is not accidentally broken.

I took the liberty of changing ((SVOP*)pl_yylval.opval)->op_sv to sv
at the same time, to make the code more readable.

1 files changed, 11 insertions, 7 deletions

diff --git a/toke.c b/toke.c
index 2a13031332..87a34dce92 100644
--- a/toke.c
+++ b/toke.c
@@ -6611,13 +6611,17 @@ Perl_yylex(pTHX)
 		if (*s == '=' && s[1] == '>' && !pkgname) {
 		    op_free(rv2cv_op);
 		    CLINE;
-		    /* This is our own scalar, created a few lines above,
-		       so this is safe. */
-		    SvREADONLY_off(cSVOPx(pl_yylval.opval)->op_sv);
-		    sv_setpv(((SVOP*)pl_yylval.opval)->op_sv, PL_tokenbuf);
-		    if (UTF && !IN_BYTES && is_utf8_string((U8*)PL_tokenbuf, len))
-		      SvUTF8_on(((SVOP*)pl_yylval.opval)->op_sv);
-		    SvREADONLY_on(cSVOPx(pl_yylval.opval)->op_sv);
+		    if (gvp || (lex && !off)) {
+			assert (cSVOPx(pl_yylval.opval)->op_sv == sv);
+			/* This is our own scalar, created a few lines
+			   above, so this is safe. */
+			SvREADONLY_off(sv);
+			sv_setpv(sv, PL_tokenbuf);
+			if (UTF && !IN_BYTES
+			 && is_utf8_string((U8*)PL_tokenbuf, len))
+			      SvUTF8_on(sv);
+			SvREADONLY_on(sv);
+		    }
 		    TERM(WORD);
 		}