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-rw-r--r--dhall_proc_macros/src/lib.rs8
-rw-r--r--dhall_proc_macros/src/parser.rs494
2 files changed, 252 insertions, 250 deletions
diff --git a/dhall_proc_macros/src/lib.rs b/dhall_proc_macros/src/lib.rs
index 37c9985..46d93e9 100644
--- a/dhall_proc_macros/src/lib.rs
+++ b/dhall_proc_macros/src/lib.rs
@@ -22,3 +22,11 @@ pub fn make_parser(input: TokenStream) -> TokenStream {
Err(err) => err.to_compile_error(),
})
}
+
+#[proc_macro]
+pub fn parse_children(input: TokenStream) -> TokenStream {
+ TokenStream::from(match parser::parse_children(input) {
+ Ok(tokens) => tokens,
+ Err(err) => err.to_compile_error(),
+ })
+}
diff --git a/dhall_proc_macros/src/parser.rs b/dhall_proc_macros/src/parser.rs
index bb4e894..2618bec 100644
--- a/dhall_proc_macros/src/parser.rs
+++ b/dhall_proc_macros/src/parser.rs
@@ -2,7 +2,11 @@ use proc_macro2::{Span, TokenStream};
use quote::quote;
use syn::parse::{Parse, ParseStream, Result};
use syn::punctuated::Punctuated;
-use syn::{bracketed, parenthesized, token, Expr, Ident, Pat, Token, Type};
+use syn::spanned::Spanned;
+use syn::{
+ bracketed, parenthesized, parse_quote, token, Error, Expr, Ident, ItemFn,
+ Pat, ReturnType, Token, Type,
+};
mod rule_kw {
syn::custom_keyword!(rule);
@@ -16,73 +20,40 @@ struct Rules(Vec<Rule>);
#[derive(Debug, Clone)]
struct Rule {
- rule_token: rule_kw::rule,
- bang_token: Token![!],
- paren_token: token::Paren,
name: Ident,
- lt_token: token::Lt,
output_type: Type,
- gt_token: token::Gt,
contents: RuleContents,
- semi_token: Token![;],
}
#[derive(Debug, Clone)]
enum RuleContents {
- Empty,
- CapturedString {
- span: Option<Ident>,
- captured_str_token: rule_kw::captured_str,
- bang_token: Token![!],
- paren_token: token::Paren,
- pattern: Pat,
- fat_arrow_token: Token![=>],
- body: Expr,
- },
- Children {
- span: Option<Ident>,
- children_token: rule_kw::children,
- bang_token: Token![!],
- paren_token: token::Paren,
- branches: Punctuated<ChildrenBranch, Token![,]>,
- },
PrecClimb {
- span: Option<Ident>,
- prec_climb_token: rule_kw::prec_climb,
- bang_token: Token![!],
- paren_token: token::Paren,
child_rule: Ident,
- comma_token: Token![,],
climber: Expr,
- comma_token2: Token![,],
- pattern: Pat,
- fat_arrow_token: Token![=>],
- body: Expr,
+ function: ItemFn,
+ },
+ Function {
+ function: ItemFn,
},
}
#[derive(Debug, Clone)]
struct ChildrenBranch {
- bracket_token: token::Bracket,
- pattern_unparsed: TokenStream,
+ pattern_span: Span,
pattern: Punctuated<ChildrenBranchPatternItem, Token![,]>,
- fat_arrow_token: Token![=>],
body: Expr,
}
#[derive(Debug, Clone)]
enum ChildrenBranchPatternItem {
- Single {
- rule_name: Ident,
- paren_token: token::Paren,
- binder: Pat,
- },
- Multiple {
- rule_name: Ident,
- paren_token: token::Paren,
- binder: Ident,
- slice_token: Token![..],
- },
+ Single { rule_name: Ident, binder: Pat },
+ Multiple { rule_name: Ident, binder: Ident },
+}
+
+#[derive(Debug, Clone)]
+struct ParseChildrenInput {
+ input_expr: Expr,
+ branches: Punctuated<ChildrenBranch, Token![,]>,
}
impl Parse for Rules {
@@ -97,73 +68,50 @@ impl Parse for Rules {
impl Parse for Rule {
fn parse(input: ParseStream) -> Result<Self> {
- let contents;
- Ok(Rule {
- rule_token: input.parse()?,
- bang_token: input.parse()?,
- paren_token: parenthesized!(contents in input),
- name: contents.parse()?,
- lt_token: contents.parse()?,
- output_type: contents.parse()?,
- gt_token: contents.parse()?,
- contents: contents.parse()?,
- semi_token: input.parse()?,
- })
- }
-}
+ let function: ItemFn = input.parse()?;
+ let (recognized_attrs, remaining_attrs) = function
+ .attrs
+ .iter()
+ .cloned()
+ .partition::<Vec<_>, _>(|attr| attr.path.is_ident("prec_climb"));
+ let function = ItemFn {
+ attrs: remaining_attrs,
+ ..(function.clone())
+ };
-impl Parse for RuleContents {
- fn parse(input: ParseStream) -> Result<Self> {
- if input.is_empty() {
- return Ok(RuleContents::Empty);
- }
- let _: Token![;] = input.parse()?;
- let span = if input.peek(Ident) && input.peek2(Token![;]) {
- let span: Ident = input.parse()?;
- let _: Token![;] = input.parse()?;
- Some(span)
- } else {
- None
+ let name = function.sig.ident.clone();
+ let output_type = match &function.sig.output {
+ ReturnType::Default => parse_quote!(()),
+ ReturnType::Type(_, t) => (**t).clone(),
};
- let lookahead = input.lookahead1();
- if lookahead.peek(rule_kw::captured_str) {
- let contents;
- Ok(RuleContents::CapturedString {
- span,
- captured_str_token: input.parse()?,
- bang_token: input.parse()?,
- paren_token: parenthesized!(contents in input),
- pattern: contents.parse()?,
- fat_arrow_token: input.parse()?,
- body: input.parse()?,
- })
- } else if lookahead.peek(rule_kw::children) {
- let contents;
- Ok(RuleContents::Children {
- span,
- children_token: input.parse()?,
- bang_token: input.parse()?,
- paren_token: parenthesized!(contents in input),
- branches: Punctuated::parse_terminated(&contents)?,
- })
- } else if lookahead.peek(rule_kw::prec_climb) {
- let contents;
- Ok(RuleContents::PrecClimb {
- span,
- prec_climb_token: input.parse()?,
- bang_token: input.parse()?,
- paren_token: parenthesized!(contents in input),
- child_rule: contents.parse()?,
- comma_token: contents.parse()?,
- climber: contents.parse()?,
- comma_token2: contents.parse()?,
- pattern: contents.parse()?,
- fat_arrow_token: contents.parse()?,
- body: contents.parse()?,
+ if recognized_attrs.is_empty() {
+ Ok(Rule {
+ name,
+ output_type,
+ contents: RuleContents::Function { function },
})
+ } else if recognized_attrs.len() != 1 {
+ Err(input.error("expected a prec_climb attribute"))
} else {
- Err(lookahead.error())
+ let attr = recognized_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))
+ })?;
+
+ Ok(Rule {
+ name,
+ output_type,
+ contents: RuleContents::PrecClimb {
+ child_rule,
+ climber,
+ function,
+ },
+ })
}
}
}
@@ -171,40 +119,52 @@ impl Parse for RuleContents {
impl Parse for ChildrenBranch {
fn parse(input: ParseStream) -> Result<Self> {
let contents;
+ let _: token::Bracket = bracketed!(contents in input);
+ let pattern_unparsed: TokenStream = contents.fork().parse()?;
+ let pattern_span = pattern_unparsed.span();
+ let pattern = Punctuated::parse_terminated(&contents)?;
+ let _: Token![=>] = input.parse()?;
+ let body = input.parse()?;
+
Ok(ChildrenBranch {
- bracket_token: bracketed!(contents in input),
- pattern_unparsed: contents.fork().parse()?,
- pattern: Punctuated::parse_terminated(&contents)?,
- fat_arrow_token: input.parse()?,
- body: input.parse()?,
+ pattern_span,
+ pattern,
+ body,
})
}
}
impl Parse for ChildrenBranchPatternItem {
fn parse(input: ParseStream) -> Result<Self> {
- let rule_name = input.parse()?;
let contents;
- let paren_token = parenthesized!(contents in input);
+ let rule_name = input.parse()?;
+ parenthesized!(contents in input);
if input.peek(Token![..]) {
- Ok(ChildrenBranchPatternItem::Multiple {
- rule_name,
- paren_token,
- binder: contents.parse()?,
- slice_token: input.parse()?,
- })
+ let binder = contents.parse()?;
+ let _: Token![..] = input.parse()?;
+ Ok(ChildrenBranchPatternItem::Multiple { rule_name, binder })
} else if input.is_empty() || input.peek(Token![,]) {
- Ok(ChildrenBranchPatternItem::Single {
- rule_name,
- paren_token,
- binder: contents.parse()?,
- })
+ let binder = contents.parse()?;
+ Ok(ChildrenBranchPatternItem::Single { rule_name, binder })
} else {
Err(input.error("expected `..` or nothing"))
}
}
}
+impl Parse for ParseChildrenInput {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let input_expr = input.parse()?;
+ let _: Token![;] = input.parse()?;
+ let branches = Punctuated::parse_terminated(input)?;
+
+ Ok(ParseChildrenInput {
+ input_expr,
+ branches,
+ })
+ }
+}
+
fn make_construct_precclimbers(rules: &Rules) -> Result<TokenStream> {
let mut entries: Vec<TokenStream> = Vec::new();
for rule in &rules.0 {
@@ -233,11 +193,16 @@ fn make_entrypoints(rules: &Rules) -> Result<TokenStream> {
entries.push(quote!(
#[allow(non_snake_case, dead_code)]
fn #name<'a>(
- input: Rc<str>,
+ input_str: &str,
pair: Pair<'a, Rule>,
- ) -> ParseResult<#output_type> {
+ ) -> #output_type {
let climbers = construct_precclimbers();
- Parsers::#name((&climbers, input), pair)
+ let input = ParseInput {
+ climbers: &climbers,
+ original_input_str: input_str.to_string().into(),
+ pair
+ };
+ Parsers::#name(input)
}
))
}
@@ -250,128 +215,37 @@ fn make_entrypoints(rules: &Rules) -> Result<TokenStream> {
))
}
-fn make_parser_branch(branch: &ChildrenBranch) -> TokenStream {
- let ChildrenBranch {
- pattern,
- body,
- pattern_unparsed,
- ..
- } = branch;
- let variable_pattern = Ident::new("variable_pattern", Span::call_site());
- let match_pat = pattern.iter().map(|item| match item {
- ChildrenBranchPatternItem::Single { rule_name, .. } => {
- quote!(Rule::#rule_name)
- }
- ChildrenBranchPatternItem::Multiple { .. } => {
- quote!(#variable_pattern..)
- }
- });
- let match_filter = pattern.iter().map(|item| match item {
- ChildrenBranchPatternItem::Single { .. } => quote!(true &&),
- ChildrenBranchPatternItem::Multiple { rule_name, .. } => {
- quote!(#variable_pattern.iter().all(|r| r == &Rule::#rule_name) &&)
- }
- });
- quote!(
- [#(#match_pat),*] if #(#match_filter)* true => {
- parse_children!((climbers, input.clone()), iter;
- [#pattern_unparsed] => {
- #[allow(unused_variables)]
- let res: Result<_, String> = try { #body };
- res.map_err(|msg|
- custom_parse_error(&pair, msg)
- )
- }
- )
- }
- )
-}
-
-fn make_parser_expr(rule: &Rule) -> Result<TokenStream> {
- let name = &rule.name;
- let expr = match &rule.contents {
- RuleContents::Empty => quote!(Ok(())),
- RuleContents::CapturedString { pattern, body, .. } => quote!(
- let #pattern = pair.as_str();
- let res: Result<_, String> = try { #body };
- res.map_err(|msg| custom_parse_error(&pair, msg))
- ),
- RuleContents::PrecClimb {
- child_rule,
- pattern,
- body,
- ..
- } => quote!(
- let climber = climbers.get(&Rule::#name).unwrap();
- climber.climb(
- pair.clone().into_inner(),
- |p| Parsers::#child_rule((climbers, input.clone()), p),
- |l, op, r| {
- let #pattern = (l?, op, r?);
- let res: Result<_, String> = try { #body };
- res.map_err(|msg| custom_parse_error(&pair, msg))
- },
- )
- ),
- RuleContents::Children { branches, .. } => {
- let branches = branches.iter().map(make_parser_branch);
- quote!(
- let children_rules: Vec<Rule> = pair
- .clone()
- .into_inner()
- .map(|p| p.as_rule())
- .collect();
-
- #[allow(unused_mut)]
- let mut iter = pair.clone().into_inner();
-
- #[allow(unreachable_code)]
- match children_rules.as_slice() {
- #(#branches,)*
- [..] => Err(custom_parse_error(
- &pair,
- format!("Unexpected children: {:?}", children_rules)
- )),
- }
- )
- }
- };
- Ok(expr)
-}
-
fn make_parsers(rules: &Rules) -> Result<TokenStream> {
- let mut entries: Vec<TokenStream> = Vec::new();
- for rule in &rules.0 {
- let span_def = match &rule.contents {
- RuleContents::CapturedString {
- span: Some(span), ..
- }
- | RuleContents::Children {
- span: Some(span), ..
- }
- | RuleContents::PrecClimb {
- span: Some(span), ..
- } => Some(quote!(
- let #span = Span::make(input.clone(), pair.as_span());
- )),
- _ => None,
- };
-
+ let entries = rules.0.iter().map(|rule| {
let name = &rule.name;
let output_type = &rule.output_type;
- let expr = make_parser_expr(rule)?;
-
- entries.push(quote!(
- #[allow(non_snake_case, dead_code)]
- fn #name<'a>(
- (climbers, input): (&HashMap<Rule, PrecClimber<Rule>>, Rc<str>),
- pair: Pair<'a, Rule>,
- ) -> ParseResult<#output_type> {
- #span_def
- #expr
- }
- ))
- }
+ match &rule.contents {
+ RuleContents::PrecClimb {
+ child_rule,
+ function,
+ ..
+ } => quote!(
+ #[allow(non_snake_case, dead_code)]
+ fn #name<'a, 'climbers>(
+ input: ParseInput<'a, 'climbers, Rule>,
+ ) -> #output_type {
+ #function
+ let climber = input.climbers.get(&Rule::#name).unwrap();
+ climber.climb(
+ input.pair.clone().into_inner(),
+ |p| Parsers::#child_rule(input.with_pair(p)),
+ |l, op, r| {
+ #name(input.clone(), l?, op, r?)
+ },
+ )
+ }
+ ),
+ RuleContents::Function { function } => quote!(
+ #[allow(non_snake_case, dead_code)]
+ #function
+ ),
+ }
+ });
Ok(quote!(
struct Parsers;
@@ -384,7 +258,7 @@ fn make_parsers(rules: &Rules) -> Result<TokenStream> {
pub fn make_parser(
input: proc_macro::TokenStream,
) -> Result<proc_macro2::TokenStream> {
- let rules: Rules = syn::parse_macro_input::parse(input.clone())?;
+ let rules: Rules = syn::parse(input.clone())?;
let construct_precclimbers = make_construct_precclimbers(&rules)?;
let entrypoints = make_entrypoints(&rules)?;
@@ -396,3 +270,123 @@ pub fn make_parser(
#parsers
))
}
+
+fn make_parser_branch(branch: &ChildrenBranch) -> Result<TokenStream> {
+ use ChildrenBranchPatternItem::{Multiple, Single};
+
+ let body = &branch.body;
+
+ // 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 that they all match the chosen Rule in the `if`-condition.
+ let variable_pattern_ident =
+ Ident::new("variable_pattern", Span::call_site());
+ let match_pat = branch.pattern.iter().map(|item| match item {
+ Single { rule_name, .. } => quote!(Rule::#rule_name),
+ Multiple { .. } => quote!(#variable_pattern_ident..),
+ });
+ let match_filter = branch.pattern.iter().map(|item| match item {
+ Single { .. } => quote!(),
+ Multiple { rule_name, .. } => quote!(
+ #variable_pattern_ident.iter().all(|r| r == &Rule::#rule_name) &&
+ ),
+ });
+
+ // Once we have found a branch that matches, we need to parse the children.
+ let mut singles_before_multiple = Vec::new();
+ let mut multiple = None;
+ let mut singles_after_multiple = Vec::new();
+ for item in &branch.pattern {
+ match item {
+ Single {
+ rule_name, binder, ..
+ } => {
+ if multiple.is_none() {
+ singles_before_multiple.push((rule_name, binder))
+ } else {
+ singles_after_multiple.push((rule_name, binder))
+ }
+ }
+ Multiple {
+ rule_name, binder, ..
+ } => {
+ if multiple.is_none() {
+ multiple = Some((rule_name, binder))
+ } else {
+ return Err(Error::new(
+ branch.pattern_span.clone(),
+ "multiple variable-length patterns are not allowed",
+ ));
+ }
+ }
+ }
+ }
+ let mut parses = Vec::new();
+ for (rule_name, binder) in singles_before_multiple.into_iter() {
+ parses.push(quote!(
+ let #binder = Parsers::#rule_name(
+ inputs.next().unwrap()
+ )?;
+ ))
+ }
+ // 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.
+ for (rule_name, binder) in singles_after_multiple.into_iter().rev() {
+ parses.push(quote!(
+ let #binder = Parsers::#rule_name(
+ inputs.next_back().unwrap()
+ )?;
+ ))
+ }
+ if let Some((rule_name, binder)) = multiple {
+ parses.push(quote!(
+ let #binder = inputs
+ .map(|i| Parsers::#rule_name(i))
+ .collect::<Result<Vec<_>, _>>()?
+ .into_iter();
+ ))
+ }
+
+ Ok(quote!(
+ [#(#match_pat),*] if #(#match_filter)* true => {
+ #(#parses)*
+ #body
+ }
+ ))
+}
+
+pub fn parse_children(
+ input: proc_macro::TokenStream,
+) -> Result<proc_macro2::TokenStream> {
+ let input: ParseChildrenInput = syn::parse(input)?;
+
+ let input_expr = &input.input_expr;
+ let branches = input
+ .branches
+ .iter()
+ .map(make_parser_branch)
+ .collect::<Result<Vec<_>>>()?;
+ Ok(quote!({
+ let children_rules: Vec<Rule> = #input_expr.pair
+ .clone()
+ .into_inner()
+ .map(|p| p.as_rule())
+ .collect();
+
+ #[allow(unused_mut)]
+ let mut inputs = #input_expr
+ .pair
+ .clone()
+ .into_inner()
+ .map(|p| #input_expr.with_pair(p));
+
+ #[allow(unreachable_code)]
+ match children_rules.as_slice() {
+ #(#branches,)*
+ [..] => return Err(#input_expr.error(
+ format!("Unexpected children: {:?}", children_rules)
+ )),
+ }
+ }))
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-23 02:15:26 +0000