Catch variable use before declaration (RT #61838)

Does not catch unused non-$ variables in double quoted strings.

This also moves $Inf and $NaN to an earlier setting file, because
they were used before the declaration.

It also contains a very ugly workaound around a problem with the nqp
%markhash being global, and reused for multiple evals. This bug
was exposed by other parts of the patch.

src/Perl6/Actions.pm

@@ -1053,6 +1053,18 @@ class Perl6::Actions is HLL::Actions {
             $past.unshift(PAST::Var.new( :name('self'), :scope('lexical_6model') ));
         }
         elsif $*IN_DECL ne 'variable' {
+            # the $*QSGIL part is a hack:
+            # when we parse double-quoted strings like "@a", the @a is
+            # first parsed as a variable, and thus checked. So it throws
+            # an exception even if turns out not to end in a postcircumfix
+            #
+            # I don't know what the correct solution is. Disabling the check
+            # inside double quotes fixes the most common case, but fails to
+            # catch undeclared variables in double-quoted strings.
+            if $sigil ne '&' && !$*IN_DECL && ($*QSIGIL eq '' || $*QSIGIL eq '$') && !$*ST.is_lexical($name) {
+                $/.CURSOR.panic("Variable $name is not predeclared");
+            }
+
             # Expect variable to have been declared somewhere.
             # Locate descriptor and thus type.
             try {

src/Perl6/Grammar.pm

@@ -28,7 +28,10 @@ grammar Perl6::Grammar is HLL::Grammar {
         my $*ST := pir::isnull($file) ??
             Perl6::SymbolTable.new(:handle(~pir::time__N())) !!
             Perl6::SymbolTable.new(:handle(~pir::time__N()), :description($file));
-
+
+        # XXX Hack: clear any marks.
+        pir::set_hll_global__vPsP(['HLL', 'Grammar'], '%!MARKHASH', nqp::null());
+
         self.comp_unit;
     }
 

src/core/Num.pm

@@ -1,10 +1,4 @@
 
-# XXX: Temporary definition of $Inf and $NaN until we have constants available
-# constant Inf = ...
-# constant NaN = ...
-my $Inf = nqp::p6box_n(pir::set__Ns('Inf'));
-my $NaN = nqp::p6box_n(pir::set__Ns('NaN'));
-
 my class Num {
     method Num() { self }
     method Bridge(Num:D:) { self }

src/core/control.pm

@@ -177,6 +177,14 @@ sub shell($cmd) {
     $status;
 }
 
+# XXX: Temporary definition of $Inf and $NaN until we have constants ava
+# need to come pretty early, because we use it in lots of setting files
+# constant Inf = ...
+# constant NaN = ...
+my $Inf = nqp::p6box_n(pir::set__Ns('Inf'));
+my $NaN = nqp::p6box_n(pir::set__Ns('NaN'));
+
+
 sub sleep($seconds = $Inf) {         # fractional seconds also allowed
     my $time1 = time;
     if $seconds ~~ $Inf {