allow backtick literals to have an end quote.

Rather than exclude ? + and *, exclude ` from literals and allow backtick
literals to be end quoted.

Allows us to follow the literal with an operator without using a space between
the two, which is very unnatural. Can write: [`,`?].

If we forget to the end quote it we end up with literal that (probably) does
not exist. It should generate an error, rather than silently give us something
we don't want.

Note that ] is still excluded from literals in positions 2+.

1 files changed, 50 insertions, 50 deletions

diff --git a/grammar/rust.lm b/grammar/rust.lm
index 446488d6..45e01d73 100644
--- a/grammar/rust.lm
+++ b/grammar/rust.lm
@@ -149,7 +149,7 @@ def macro_rules_tail
 |	[]
 
 def macro_rules
-	[macro_rule macro_rules_tail `; ?]
+	[macro_rule macro_rules_tail `;`?]
 
 def macro_rules_def
 	[`( macro_rules `) `;]
@@ -194,7 +194,7 @@ def use_as_opt
 
 def use_tree
 	[use_path_opt `*]
-|	[use_path_opt `{ use_tree use_list_tail `, ? `}]
+|	[use_path_opt `{ use_tree use_list_tail `,`? `}]
 |	[simple_path use_as_opt]
 
 def use_declaration
@@ -210,12 +210,12 @@ def literal_pattern
 |	[char]
 |	[string]
 |	[raw_string]
-|	[`- ? number]
-|	[`- ? float]
+|	[`-`? number]
+|	[`-`? float]
 
 def identifier_pattern
-	[`ref ? `mut ? id]
-|	[`ref ? `mut ? id `@ pattern]
+	[`ref`? `mut`? id]
+|	[`ref`? `mut`? id `@ pattern]
 
 def wildcard_pattern
 	[`_]
@@ -228,8 +228,8 @@ def range_pattern
 |	[range_pattern_bound `... range_pattern_bound]
 
 def reference_pattern
-	[`& `mut ? pattern]
-|	[`&& `mut ? pattern]
+	[`& `mut`? pattern]
+|	[`&& `mut`? pattern]
 
 #
 # struct pattern
@@ -237,7 +237,7 @@ def reference_pattern
 def struct_pattern_field
 	[number `: pattern]
 |	[id `: pattern]
-|	[`ref ? `mut ? id]
+|	[`ref`? `mut`? id]
 
 def struct_pattern_fields
 	[struct_pattern_fields `, struct_pattern_field]
@@ -268,7 +268,7 @@ def tuple_struct_items
 |	[tuple_struct_item]
 
 def tuple_struct_pattern
-	[path_in_expression `( tuple_struct_items `, ? `)]
+	[path_in_expression `( tuple_struct_items `,`? `)]
 
 def tuple_pattern_item
 	[pattern]
@@ -281,7 +281,7 @@ def tuple_pattern_items
 def tuple_pattern
 	[`( `)]
 |	[`( tuple_pattern_item `, `)]
-|	[`( tuple_pattern_item `, tuple_pattern_items `, ? `)]
+|	[`( tuple_pattern_item `, tuple_pattern_items `,`? `)]
 
 def grouped_pattern
 	[`( pattern `)]
@@ -295,7 +295,7 @@ def pattern_list
 # allowing it.
 #
 def slice_pattern
-	[`[ pattern `, pattern_list `, ? `]]
+	[`[ pattern `, pattern_list `,`? `]]
 |	[`[ pattern `, `]]
 |	[`[ pattern `]]
 |	[`[ `]]
@@ -328,11 +328,11 @@ def match_expression
 	[`match expression `{ match_arms? `}]
 
 def match_arms_last
-	[match_arm `=> block_expression `, ?]
-|	[match_arm `=> expression `, ?]
+	[match_arm `=> block_expression `,`?]
+|	[match_arm `=> expression `,`?]
 
 def match_arms_first_case
-	[match_arm `=> block_expression `, ?]
+	[match_arm `=> block_expression `,`?]
 |	[match_arm `=> expression `,]
 
 def match_arms_first_list
@@ -350,7 +350,7 @@ def match_arms_pattern_tail
 |	[]
 
 def match_arm_patterns
-	[`| ? pattern match_arms_pattern_tail]
+	[`|`? pattern match_arms_pattern_tail]
 
 def opt_match_arm_guard
 	[`if expression]
@@ -391,9 +391,9 @@ def lifetime_list
 	[lifetime lifetime_tail]
 
 def opt_type_params
-	[`< lifetime_list `, ? `>]
-|	[`< type_list `, ? `>]
-|	[`< lifetime_list `, type_list `, ? `>]
+	[`< lifetime_list `,`? `>]
+|	[`< type_list `,`? `>]
+|	[`< lifetime_list `, type_list `,`? `>]
 |	[]
 
 
@@ -419,7 +419,7 @@ def func_param_tail
 |	[]
 
 def function_parameters
-	[function_param func_param_tail `, ?]
+	[function_param func_param_tail `,`?]
 
 def function
 	[
@@ -432,10 +432,10 @@ def function
 #
 
 def self_param
-	[`mut ? `self]
-|	[`& `mut ? `self]
-|	[`& lifetime `mut ? `self]
-|	[`mut ? `self `: type]
+	[`mut`? `self]
+|	[`& `mut`? `self]
+|	[`& lifetime `mut`? `self]
+|	[`mut`? `self `: type]
 
 def opt_method_params
 	[`, function_parameters]
@@ -475,7 +475,7 @@ def opt_arrow_type
 |	[]
 
 def type_path_fn_inputs
-	[type_list `, ?]
+	[type_list `,`?]
 
 def type_path_tail
 	[type_path_tail `:: type_path_segment]
@@ -505,7 +505,7 @@ def raw_pointer_type
 def tuple_type
 	[`( `)]
 |	[`( type `, `)]
-|	[`( type `, type_list `, ? `)]
+|	[`( type `, type_list `,`? `)]
 
 def trait_object_type
 	[`dyn ? type_param_bounds]
@@ -542,7 +542,7 @@ def maybe_named_param_tail
 |	[]
 
 def maybe_named_function_parameters
-	[maybe_named_param maybe_named_param_tail `, ?]
+	[maybe_named_param maybe_named_param_tail `,`?]
 
 def maybe_named_param
 	[id `: type]
@@ -611,7 +611,7 @@ def cons_plus
 |	[_construct]
 
 def cons_list
-	[cons_plus `, ?]
+	[cons_plus `,`?]
 |	[]
 
 
@@ -631,13 +631,13 @@ def path_expr_segment
 
 def generic_args
 	[`< `>]
-|	[`< generic_args_lifetimes `, ? `>]
-|	[`< generic_args_types `, ? `>]
-|	[`< generic_args_bindings `, ? `>]
-|	[`< generic_args_types `, generic_args_bindings `, ? `>]
-|	[`< generic_args_lifetimes `, generic_args_types `, ? `>]
-|	[`< generic_args_lifetimes `, generic_args_bindings `, ? `>]
-|	[`< generic_args_lifetimes `, generic_args_types `, generic_args_bindings `, ? `>]
+|	[`< generic_args_lifetimes `,`? `>]
+|	[`< generic_args_types `,`? `>]
+|	[`< generic_args_bindings `,`? `>]
+|	[`< generic_args_types `, generic_args_bindings `,`? `>]
+|	[`< generic_args_lifetimes `, generic_args_types `,`? `>]
+|	[`< generic_args_lifetimes `, generic_args_bindings `,`? `>]
+|	[`< generic_args_lifetimes `, generic_args_types `, generic_args_bindings `,`? `>]
 
 def generic_args_lifetimes
 	[lifetime_list]
@@ -672,10 +672,10 @@ def path_expression
 
 def tuple_expression
 	[`( expression `, `)]
-|	[`( expression `, expr_list `, ? `)]
+|	[`( expression `, expr_list `,`? `)]
 
 def array_expression
-	[`[ expr_list `, ? `]]
+	[`[ expr_list `,`? `]]
 |	[`[ expression `; expression `]]
 
 def closure_parameters
@@ -687,7 +687,7 @@ def closure_param
 |	[pattern `: type]
 
 def closure_expression_param_forms
-	[`| closure_parameters `, ? `|]
+	[`| closure_parameters `,`? `|]
 |	[`||]
 
 def closure_expression
@@ -721,8 +721,8 @@ def paths
 def func_index
 	[func_index `. path_expr_segment]
 |	[func_index `. number]
-|	[func_index `( expr_list `, ? `)]
-|	[func_index `[ expr_list `, ? `]]
+|	[func_index `( expr_list `,`? `)]
+|	[func_index `[ expr_list `,`? `]]
 |	[func_index `?]
 |	[paths]
 
@@ -931,7 +931,7 @@ def tpb_tail
 	[`+ type_param_bound]
 
 def type_param_bounds
-	[type_param_bound tpb_tail* `+ ?]
+	[type_param_bound tpb_tail* `+`?]
 
 #
 # Type Params
@@ -974,7 +974,7 @@ def opt_generics
 #
 
 def lifetime_params
-	[lifetime_param_list? `, ?]
+	[lifetime_param_list? `,`?]
 
 def for_lifetimes
 	[`for `< lifetime_params `>]
@@ -984,7 +984,7 @@ def lifetime_bounds_list
 |	[lifetime]
 
 def lifetime_bounds
-	[lifetime_bounds_list? `+ ?]
+	[lifetime_bounds_list? `+`?]
 
 def lifetime_where_clause_item
 	[lifetime `: lifetime_bounds]
@@ -1001,7 +1001,7 @@ def where_clause_item_list
 |	[where_clause_item]
 
 def opt_where_clause
-	[`where where_clause_item_list `, ? ]
+	[`where where_clause_item_list `,`? ]
 |	[]
 
 
@@ -1017,7 +1017,7 @@ def tuple_field_list
 |	[tuple_field]
 
 def tuple_fields
-	[tuple_field_list `, ?]
+	[tuple_field_list `,`?]
 
 #
 # Structure
@@ -1031,7 +1031,7 @@ def struct_field_list
 |	[struct_field]
 
 def struct_fields
-	[struct_field_list `, ?]
+	[struct_field_list `,`?]
 
 def struct_struct
 	[`struct id opt_generics opt_where_clause `{ struct_fields? `}]
@@ -1169,7 +1169,7 @@ def extern_crate
 	[`extern `crate crate_ref as_clause? `;]
 
 def enum
-	[`enum id opt_generics opt_where_clause `{ enum_items? `, ? `}]
+	[`enum id opt_generics opt_where_clause `{ enum_items? `,`? `}]
 
 def enum_items
 	[enum_items `, enum_item]
@@ -1185,20 +1185,20 @@ def enum_item_tuple
 	[`( tuple_fields? `)]
 
 def enum_item_struct
-	[`{ field_list `, ? `}]
+	[`{ field_list `,`? `}]
 
 def enum_item_discriminant
 	[`= expression]
 
 def static_item
-	[`static `mut ? id `: type `= expression `;]
+	[`static `mut`? id `: type `= expression `;]
 
 def abi
 	[string]
 |	[raw_string]
 
 def external_static_item
-	[`static `mut ? id `: type `;]
+	[`static `mut`? id `: type `;]
 
 def function_return_type
 	[`-> type]