throw ex for usage of $foo before $^foo in sub body (RT #123470)

rakudo · Dec 21, 2014 · 4569b17 · 4569b17
1 parent 08c2b0f
commit 4569b17
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diff --git a/src/Perl6/Actions.nqp b/src/Perl6/Actions.nqp
@@ -2397,6 +2397,15 @@ class Perl6::Actions is HLL::Actions does STDActions {
                                                                 [];
         }
         my @params := %sig_info<parameters>;
+        for @params -> {
+            if $block.ann('also_uses') && $block.ann('also_uses'){$_<variable_name>} {
+                $*W.throw($/, ['X', 'Placeholder', 'NonPlaceholder'],
+                    placeholder   => $_<placeholder>,
+                    variable_name => $_<variable_name>,
+                    decl          => $*IN_DECL,
+                )
+            }
+        }
         set_default_parameter_type(@params, 'Any');
         my $signature := create_signature_object($<multisig> ?? $<multisig> !! $/, %sig_info, $block);
         add_signature_binding_code($block, $signature, @params);

diff --git a/src/core/Exception.pm b/src/core/Exception.pm
@@ -581,6 +581,17 @@ my class X::Placeholder::Block does X::Comp {
     }
 }
 
+my class X::Placeholder::NonPlaceholder does X::Comp {
+    has $.variable_name;
+    has $.placeholder;
+    has $.decl;
+    method message() {
+        my $decl = $!decl ?? ' ' ~ $!decl !! '';
+        "$!variable_name has already been used as a non-placeholder in the surrounding$decl block,\n" ~
+        "  so you will confuse the reader if you suddenly declare $!placeholder here"
+    }
+}
+
 my class X::Placeholder::Mainline is X::Placeholder::Block {
     method message() {
         "Cannot use placeholder parameter $.placeholder in the mainline"