Fixes description of exception

Closes #833

doc/Type/X/TypeCheck/Splice.pod6

@@ -13,22 +13,22 @@ For example
 
 =for code :skip-test
 use experimental :macros;
-macro a { 'foo' };
-say a;
+macro quasi-ast { quasi { {{{'not AST'}}} };};
+say quasi-ast;
 
 dies with
 
 =for code :skip-test
 ===SORRY!===
-Type check failed in macro application; expected AST but got Str
+Type check failed in macro application; expected AST but got Str("not AST")
 
-To fix, instead write
+This is because you are purposefully creating something that does not evaluate to an abstract syntax tree. To fix, instead write
 
     use experimental :macros;
-    macro a {
-        quasi { 'foo' }
+    macro an-ast {
+        quasi { 'yes AST' }
     }
-    say a;              # foo
+    say an-ast;              # yes AST
 
 =head1 Methods