Catch routine redeclaration in actions, rather than leaving it to IMC…

…C to whine about.

NOMMAP.markdown

@@ -20,8 +20,6 @@ Things that aren't blockers but might be worth knowing about:
   (known - multis in nested lexical scopes in general just NYI - jnthn)
 * 'has num $.attr' segfaults on access to .attr, because it uses the PMC form
   of get_attribute
-* two protos of the same name in the same scope produce an IMCC error
-  "error:imcc:Multiple declarations of lexical '&foo'"
 
 ## Lexical Multi-Part names
 For my X::Base { ... }, my Foo::Bar { ... } etc. The our-scoped ones work.

src/Perl6/Actions.pm

@@ -1144,6 +1144,10 @@ class Perl6::Actions is HLL::Actions {
             }
             else {
                 # Install.
+                if $outer.symbol($name) {
+                    $/.CURSOR.panic("Illegal redeclaration of routine '" ~
+                        ~$<deflongname>[0].ast ~ "'");
+                }
                 if $*SCOPE eq '' || $*SCOPE eq 'my' {
                     $*ST.install_lexical_symbol($outer, $name, $code);
                 }