From 9f1c5fe4c5ea275f85d8920351591378dd87ab71 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Thu, 5 Sep 2019 22:42:36 +0200 Subject: Implement rule shortcutting, and cleanup make_parser code --- dhall_proc_macros/src/make_parser.rs | 234 ++++++++++++++++++++++++++--------- 1 file changed, 173 insertions(+), 61 deletions(-) (limited to 'dhall_proc_macros/src') diff --git a/dhall_proc_macros/src/make_parser.rs b/dhall_proc_macros/src/make_parser.rs index 3375c39..a17ab61 100644 --- a/dhall_proc_macros/src/make_parser.rs +++ b/dhall_proc_macros/src/make_parser.rs @@ -2,53 +2,122 @@ use std::collections::HashMap; use std::iter; use quote::quote; -use syn::parse::{ParseStream, Result}; +use syn::parse::{Parse, ParseStream, Result}; use syn::spanned::Spanned; use syn::{ parse_quote, Error, Expr, FnArg, Ident, ImplItem, ImplItemMethod, ItemImpl, - Pat, Signature, Token, + LitBool, Pat, Token, }; +mod kw { + syn::custom_keyword!(shortcut); +} + +struct AliasArgs { + target: Ident, + is_shortcut: bool, +} + +struct PrecClimbArgs { + child_rule: Ident, + climber: Expr, +} + +struct AliasSrc { + ident: Ident, + is_shortcut: bool, +} + +struct ParsedFn<'a> { + // Body of the function + function: &'a mut ImplItemMethod, + // Name of the function. + fn_name: Ident, + // Name of the first argument of the function, which should be of type `ParseInput`. + input_arg: Ident, + // List of aliases pointing to this function + alias_srcs: Vec, +} + +impl Parse for AliasArgs { + fn parse(input: ParseStream) -> Result { + let target = input.parse()?; + let is_shortcut = if input.peek(Token![,]) { + // #[alias(rule, shortcut = true)] + let _: Token![,] = input.parse()?; + let _: kw::shortcut = input.parse()?; + let _: Token![=] = input.parse()?; + let b: LitBool = input.parse()?; + b.value + } else { + // #[alias(rule)] + false + }; + Ok(AliasArgs { + target, + is_shortcut, + }) + } +} + +impl Parse for PrecClimbArgs { + fn parse(input: ParseStream) -> Result { + let child_rule = input.parse()?; + let _: Token![,] = input.parse()?; + let climber = input.parse()?; + Ok(PrecClimbArgs { + child_rule, + climber, + }) + } +} + fn collect_aliases( imp: &mut ItemImpl, -) -> Result)>> { +) -> Result>> { + let functions = imp.items.iter_mut().flat_map(|item| match item { + ImplItem::Method(m) => Some(m), + _ => None, + }); + let mut alias_map = HashMap::new(); + for function in functions { + let fn_name = function.sig.ident.clone(); + let mut alias_attrs = function + .attrs + .drain_filter(|attr| attr.path.is_ident("alias")) + .collect::>() + .into_iter(); - for item in &mut imp.items { - if let ImplItem::Method(function) = item { - let fn_name = function.sig.ident.clone(); - let mut alias_attrs = function - .attrs - .drain_filter(|attr| attr.path.is_ident("alias")) - .collect::>() - .into_iter(); - - if let Some(attr) = alias_attrs.next() { - let tgt: Ident = attr.parse_args()?; - alias_map - .entry(tgt) - .or_insert_with(|| (function.sig.clone(), Vec::new())) - .1 - .push(fn_name); - } - if let Some(attr) = alias_attrs.next() { - return Err(Error::new( - attr.span(), - "expected at most one alias attribute", - )); - } + if let Some(attr) = alias_attrs.next() { + let args: AliasArgs = attr.parse_args()?; + alias_map.entry(args.target).or_insert_with(Vec::new).push( + AliasSrc { + ident: fn_name, + is_shortcut: args.is_shortcut, + }, + ); + } + if let Some(attr) = alias_attrs.next() { + return Err(Error::new( + attr.span(), + "expected at most one alias attribute", + )); } } Ok(alias_map) } -fn parse_rulefn_sig(sig: &Signature) -> Result<(Ident, Ident)> { - let fn_name = sig.ident.clone(); +fn parse_fn<'a>( + function: &'a mut ImplItemMethod, + alias_map: &mut HashMap>, +) -> Result> { + let fn_name = function.sig.ident.clone(); // Get the name of the first (`input`) function argument - let input_arg = sig.inputs.first().ok_or_else(|| { + let input_arg = function.sig.inputs.first().ok_or_else(|| { Error::new( - sig.inputs.span(), + function.sig.inputs.span(), "a rule function needs an `input` argument", ) })?; @@ -66,21 +135,26 @@ fn parse_rulefn_sig(sig: &Signature) -> Result<(Ident, Ident)> { } }; - Ok((fn_name, input_arg)) + let alias_srcs = alias_map.remove(&fn_name).unwrap_or_else(Vec::new); + + Ok(ParsedFn { + function, + fn_name, + input_arg, + alias_srcs, + }) } -fn apply_special_attrs( - function: &mut ImplItemMethod, - alias_map: &mut HashMap)>, - rule_enum: &Ident, -) -> Result<()> { +fn apply_special_attrs(f: &mut ParsedFn, rule_enum: &Ident) -> Result<()> { + let function = &mut *f.function; + let fn_name = &f.fn_name; + let input_arg = &f.input_arg; + *function = parse_quote!( - #[allow(non_snake_case, dead_code)] + #[allow(non_snake_case)] #function ); - let (fn_name, input_arg) = parse_rulefn_sig(&function.sig)?; - // `prec_climb` attr let prec_climb_attrs: Vec<_> = function .attrs @@ -96,13 +170,10 @@ fn apply_special_attrs( // do nothing } else { let attr = prec_climb_attrs.into_iter().next().unwrap(); - let (child_rule, climber) = - attr.parse_args_with(|input: ParseStream| { - let child_rule: Ident = input.parse()?; - let _: Token![,] = input.parse()?; - let climber: Expr = input.parse()?; - Ok((child_rule, climber)) - })?; + let PrecClimbArgs { + child_rule, + climber, + } = attr.parse_args()?; function.block = parse_quote!({ #function @@ -129,9 +200,24 @@ fn apply_special_attrs( } // `alias` attr - if let Some((_, aliases)) = alias_map.remove(&fn_name) { + if !f.alias_srcs.is_empty() { + let aliases = f.alias_srcs.iter().map(|src| &src.ident); let block = &function.block; function.block = parse_quote!({ + let mut #input_arg = #input_arg; + // While the current rule allows shortcutting, and there is a single child, and the + // child can still be parsed by the current function, then skip to that child. + while ::allows_shortcut(#input_arg.as_rule()) { + if let Some(child) = #input_arg.single_child() { + if &::rule_alias(child.as_rule()) + == stringify!(#fn_name) { + #input_arg = child; + continue; + } + } + break + } + match #input_arg.as_rule() { #(#rule_enum::#aliases => Self::#aliases(#input_arg),)* #rule_enum::#fn_name => #block, @@ -157,36 +243,56 @@ pub fn make_parser( let mut alias_map = collect_aliases(&mut imp)?; let rule_alias_branches: Vec<_> = alias_map .iter() - .flat_map(|(tgt, (_, srcs))| iter::repeat(tgt).zip(srcs)) + .flat_map(|(tgt, srcs)| iter::repeat(tgt).zip(srcs)) .map(|(tgt, src)| { + let ident = &src.ident; + quote!( + #rule_enum::#ident => stringify!(#tgt).to_string(), + ) + }) + .collect(); + let shortcut_branches: Vec<_> = alias_map + .iter() + .flat_map(|(_tgt, srcs)| srcs) + .map(|AliasSrc { ident, is_shortcut }| { quote!( - #rule_enum::#src => stringify!(#tgt).to_string(), + #rule_enum::#ident => #is_shortcut, ) }) .collect(); - imp.items + let fn_map: HashMap = imp + .items .iter_mut() - .map(|item| match item { - ImplItem::Method(m) => { - apply_special_attrs(m, &mut alias_map, &rule_enum) - } - _ => Ok(()), + .flat_map(|item| match item { + ImplItem::Method(m) => Some(m), + _ => None, }) - .collect::>()?; + .map(|method| { + let mut f = parse_fn(method, &mut alias_map)?; + apply_special_attrs(&mut f, &rule_enum)?; + Ok((f.fn_name.clone(), f)) + }) + .collect::>()?; // Entries that remain in the alias map don't have a matching method, so we create one. let extra_fns: Vec<_> = alias_map .iter() - .map(|(tgt, (sig, srcs))| { - let mut sig = sig.clone(); + .map(|(tgt, srcs)| { + // Get the signature of one of the functions that has this alias. They should all have + // essentially the same signature anyways. + let f = fn_map.get(&srcs.first().unwrap().ident).unwrap(); + let input_arg = f.input_arg.clone(); + let mut sig = f.function.sig.clone(); sig.ident = tgt.clone(); + let srcs = srcs.iter().map(|src| &src.ident); - let (_, input_arg) = parse_rulefn_sig(&sig)?; - Ok(ImplItem::Method(parse_quote!( + Ok(parse_quote!( #sig { match #input_arg.as_rule() { #(#rule_enum::#srcs => Self::#srcs(#input_arg),)* + // We can't match on #rule_enum::#tgt since `tgt` might be an arbitrary + // identifier. r if &format!("{:?}", r) == stringify!(#tgt) => return Err(#input_arg.error(format!( "make_parser: missing method for rule {}", @@ -199,7 +305,7 @@ pub fn make_parser( ) } } - ))) + )) }) .collect::>()?; imp.items.extend(extra_fns); @@ -215,6 +321,12 @@ pub fn make_parser( r => format!("{:?}", r), } } + fn allows_shortcut(rule: Self::Rule) -> bool { + match rule { + #(#shortcut_branches)* + _ => false, + } + } } #imp -- cgit v1.2.3