Return type in prototype does not work when the last parameter has a default value

[baby-gnu]

Hello,

Doing some tests with Kavorka features show me an issue when the last parameter has a default value.

Here are some tests to add to t/80returntype.t:

diff --git a/t/80returntype.t b/t/80returntype.t
index dbb4a14..fa2d185 100644
--- a/t/80returntype.t
+++ b/t/80returntype.t
@@ -67,4 +67,23 @@ is_deeply( [add3(4,5)], [4,5] );
 like(exception { my @r = add3(4.1,4.9) }, qr{did not pass type constraint "ArrayRef.Int." at \S+ line 67});
 like(exception { my @r = add3(4.1,5) }, qr{did not pass type constraint "ArrayRef.Int." at \S+ line 68});
 
+fun add4($a, $b? → Int){
+	if ($b) {
+		return $a + $b;
+	}
+	else {
+		return $a+1;
+	}
+}
+
+is( add4(1,2), 3, 'return type constraint works with optional parameter set');
+is( add4(1), 2, 'return type constraint works with optional parameter unset');
+
+fun add5($a, $b = 1 → Int) {
+	return $a + $b;
+}
+
+is( add4(1,2), 3, 'return type constraint works with default parameter set');
+is( add4(1), 2, 'return type constraint works with default parameter unset');
+
 done_testing;

The test does not compile at all:

prove -rlv t/80returntype.t 
t/80returntype.t .. Unrecognized character \x{2192}; marked by <-- HERE after a, $b = 1 <-- HERE near column 21 at t/80returntype.t line 82.
Dubious, test returned 255 (wstat 65280, 0xff00)
No subtests run 

Test Summary Report
-------------------
t/80returntype.t (Wstat: 65280 Tests: 0 Failed: 0)
  Non-zero exit status: 255
  Parse errors: No plan found in TAP output
Files=1, Tests=0,  1 wallclock secs ( 0.02 usr  0.00 sys +  0.28 cusr  0.01 csys =  0.31 CPU)
Result: FAIL

I tracked the problem up to Kavorka::Parameter::parse

Set a debug point:

diff --git a/lib/Kavorka/Parameter.pm b/lib/Kavorka/Parameter.pm
index f709630..631fcdb 100644
--- a/lib/Kavorka/Parameter.pm
+++ b/lib/Kavorka/Parameter.pm
@@ -271,6 +271,7 @@ sub parse
 	
 	if (lex_peek(5) =~ m{ \A ( (?: [/]{2} | [|]{2} )?= ) }x)
 	{
+		$DB::single = 1;
 		$default_when = $1;
 		lex_read(length($1));
 		lex_read_space;

Which results in the following trace:

perl -I lib/ -d t/80returntype.t 

Loading DB routines from perl5db.pl version 1.49_05
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

Kavorka::Parameter::parse(lib/Kavorka/Parameter.pm:275):
275:			$default_when = $1;
  DB<1> n
Kavorka::Parameter::parse(lib/Kavorka/Parameter.pm:276):
276:			lex_read(length($1));
  DB<1> 
Kavorka::Parameter::parse(lib/Kavorka/Parameter.pm:277):
277:			lex_read_space;
278:			$default = lex_peek(5) =~ m{ \A (?: when\b | [,)] ) }x
  DB<1> 
Kavorka::Parameter::parse(lib/Kavorka/Parameter.pm:280):
280:				: parse_arithexpr;
  DB<1> 
Unrecognized character \x{2192}; marked by <-- HERE after a, $b = 1 <-- HERE near column 21 at t/80returntype.t line 82.
 at lib/Kavorka/Signature.pm line 73.
	Kavorka::Signature::parse("Kavorka::Signature", "package", "main", "_is_dummy", 0) called at lib/Kavorka/Sub.pm line 221
	Kavorka::Sub::parse_signature(Kavorka::Sub::Fun=HASH(0x561606be0968)) called at lib/Kavorka/Sub.pm line 123
	Kavorka::Sub::parse("Kavorka::Sub::Fun", "keyword", "fun") called at lib/Kavorka.pm line 187
	Kavorka::parse_fun("fun") called at t/80returntype.t line 82
Debugged program terminated.  Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.

Regards.

[tobyink]

Same as https://rt.cpan.org/Ticket/Display.html?id=97782