diff options
Diffstat (limited to '')
| -rw-r--r-- | pest_consume_macros/src/match_nodes.rs | 79 |
1 files changed, 47 insertions, 32 deletions
diff --git a/pest_consume_macros/src/match_nodes.rs b/pest_consume_macros/src/match_nodes.rs index 4d9fd52..e4cd1e6 100644 --- a/pest_consume_macros/src/match_nodes.rs +++ b/pest_consume_macros/src/match_nodes.rs @@ -90,6 +90,7 @@ impl Parse for ParseChildrenInput { fn make_parser_branch( branch: &ChildrenBranch, i_inputs: &Ident, + i_input_rules: &Ident, parser: &Type, ) -> Result<TokenStream> { use ChildrenBranchPatternItem::{Multiple, Single}; @@ -97,33 +98,8 @@ fn make_parser_branch( let body = &branch.body; let aliased_rule = quote!(<#parser as ::pest_consume::Parser>::AliasedRule); - // Convert the input pattern into a pattern-match on the Rules of the children. This uses - // slice_patterns. - // A single pattern just checks that the rule matches; a variable-length pattern binds the - // subslice and checks, in the if-guard, that its elements all match the chosen Rule. - let i_variable_pattern = - Ident::new("___variable_pattern", Span::call_site()); - let match_pat = branch.pattern.iter().map(|item| match item { - Single { rule_name, .. } => quote!(#aliased_rule::#rule_name), - Multiple { .. } => quote!(#i_variable_pattern @ ..), - }); - let match_filter = branch.pattern.iter().map(|item| match item { - Single { .. } => quote!(), - Multiple { rule_name, .. } => quote!( - { - // We can't use .all() directly in the pattern guard; see - // https://github.com/rust-lang/rust/issues/59803. - let all_match = |slice: &[_]| { - slice.iter().all(|r| - *r == #aliased_rule::#rule_name - ) - }; - all_match(#i_variable_pattern) - } && - ), - }); - - // Once we have found a branch that matches, we need to parse the children. + // Patterns all have the form [a, b, c.., d], with a bunch of simple patterns, + // optionally a multiple pattern, and then some more simple patterns. let mut singles_before_multiple = Vec::new(); let mut multiple = None; let mut singles_after_multiple = Vec::new(); @@ -152,6 +128,45 @@ fn make_parser_branch( } } } + + // Find which branch to take + let mut conditions = Vec::new(); + let start = singles_before_multiple.len(); + let end = singles_after_multiple.len(); + conditions.push(quote!( + #start + #end <= #i_input_rules.len() + )); + for (i, (rule_name, _)) in singles_before_multiple.iter().enumerate() { + conditions.push(quote!( + #i_input_rules[#i] == #aliased_rule::#rule_name + )) + } + for (i, (rule_name, _)) in singles_after_multiple.iter().enumerate() { + conditions.push(quote!( + #i_input_rules[#i_input_rules.len()-1 - #i] == #aliased_rule::#rule_name + )) + } + if let Some((rule_name, _)) = multiple { + conditions.push(quote!( + { + // We can't use .all() directly in the pattern guard; see + // https://github.com/rust-lang/rust/issues/59803. + let all_match = |slice: &[_]| { + slice.iter().all(|r| + *r == #aliased_rule::#rule_name + ) + }; + all_match(&#i_input_rules[#start..#i_input_rules.len() - #end]) + } + )) + } else { + // No variable-length pattern, so the size must be exactly the number of patterns + conditions.push(quote!( + #start + #end == #i_input_rules.len() + )) + } + + // Once we have found a branch that matches, we need to parse the children. let mut parses = Vec::new(); for (rule_name, binder) in singles_before_multiple.into_iter() { parses.push(quote!( @@ -161,7 +176,7 @@ fn make_parser_branch( )) } // Note the `rev()`: we are taking inputs from the end of the iterator in reverse order, so that - // only the unmatched inputs are left for the variable-length pattern, if any. + // only the unmatched inputs are left in the iterator for the variable-length pattern, if any. for (rule_name, binder) in singles_after_multiple.into_iter().rev() { parses.push(quote!( let #binder = #parser::#rule_name( @@ -179,7 +194,7 @@ fn make_parser_branch( } Ok(quote!( - [#(#match_pat),*] if #(#match_filter)* true => { + _ if #(#conditions &&)* true => { #(#parses)* #body } @@ -199,7 +214,7 @@ pub fn match_nodes( let branches = input .branches .iter() - .map(|br| make_parser_branch(br, &i_inputs, parser)) + .map(|br| make_parser_branch(br, &i_inputs, &i_input_rules, parser)) .collect::<Result<Vec<_>>>()?; Ok(quote!({ @@ -208,9 +223,9 @@ pub fn match_nodes( let #i_input_rules = #i_inputs.aliased_rules::<#parser>(); #[allow(unreachable_code)] - match #i_input_rules.as_slice() { + match () { #(#branches,)* - [..] => return ::std::result::Result::Err(#i_inputs.error( + _ => return ::std::result::Result::Err(#i_inputs.error( std::format!("Unexpected children: {:?}", #i_input_rules) )), } |