Units: add a test case for FunctionParameters subparser

Units/simple-function-parameters.d/args.ctags

@@ -0,0 +1,2 @@
+--sort=no
+--fields=+lK

Units/simple-function-parameters.d/expected.tags

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+foo	input.pl	/^fun foo($x, $y, $z = 5) {$/;"	fun	language:FunctionParameters
+bar	input.pl	/^method bar($label, $n) {$/;"	method	language:FunctionParameters
+create_point	input.pl	/^fun create_point(:$x, :$y, :$color) {$/;"	fun	language:FunctionParameters
+Derived	input.pl	/^package Derived {$/;"	package	language:Perl
+Derived	input.pl	/^package Derived {$/;"	class	language:Moose
+go_big	input.pl	/^    has 'go_big' => ($/;"	attribute	language:Moose	class:Derived

Units/simple-function-parameters.d/input.pl

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+# Taken from https://metacpan.org/pod/Function::Parameters
+use Function::Parameters;
+
+# plain function
+fun foo($x, $y, $z = 5) {
+    return $x + $y + $z;
+}
+print foo(1, 2), "\n";  # 8
+
+# method with implicit $self
+method bar($label, $n) {
+    return "$label: " . ($n * $self->scale);
+}
+
+# named arguments: order doesn't matter in the call
+fun create_point(:$x, :$y, :$color) {
+    print "creating a $color point at ($x, $y)\n";
+}
+create_point(
+    color => "red",
+    x     => 10,
+    y     => 5,
+);
+
+package Derived {
+    use Function::Parameters qw(:std :modifiers);
+    use Moo;
+
+    extends 'Base';
+
+    has 'go_big' => (
+        is => 'ro',
+    );
+
+    # "around" method with implicit $orig and $self
+    around size() {
+        return $self->$orig() * 2 if $self->go_big;
+        return $self->$orig();
+    }
+}