Merge pull request #113 from Nadrieril/pest_consume

Extract parser macros into an independent crate

3 files changed, 0 insertions, 568 deletions

diff --git a/dhall_proc_macros/src/lib.rs b/dhall_proc_macros/src/lib.rs
index 37e8f9f..5304429 100644
--- a/dhall_proc_macros/src/lib.rs
+++ b/dhall_proc_macros/src/lib.rs
@@ -1,4 +1,3 @@
-#![feature(drain_filter)]
 //! This crate contains the code-generation primitives for the [dhall-rust][dhall-rust] crate.
 //! This is highly unstable and breaks regularly; use at your own risk.
 //!
@@ -7,8 +6,6 @@
 extern crate proc_macro;
 
 mod derive;
-mod make_parser;
-mod parse_children;
 
 use proc_macro::TokenStream;
 
@@ -16,19 +13,3 @@ use proc_macro::TokenStream;
 pub fn derive_static_type(input: TokenStream) -> TokenStream {
     derive::derive_static_type(input)
 }
-
-#[proc_macro_attribute]
-pub fn make_parser(attrs: TokenStream, input: TokenStream) -> TokenStream {
-    TokenStream::from(match make_parser::make_parser(attrs, input) {
-        Ok(tokens) => tokens,
-        Err(err) => err.to_compile_error(),
-    })
-}
-
-#[proc_macro]
-pub fn parse_children(input: TokenStream) -> TokenStream {
-    TokenStream::from(match parse_children::parse_children(input) {
-        Ok(tokens) => tokens,
-        Err(err) => err.to_compile_error(),
-    })
-}
diff --git a/dhall_proc_macros/src/make_parser.rs b/dhall_proc_macros/src/make_parser.rs
deleted file mode 100644
index a17ab61..0000000
--- a/dhall_proc_macros/src/make_parser.rs
+++ /dev/null
@@ -1,334 +0,0 @@
-use std::collections::HashMap;
-use std::iter;
-
-use quote::quote;
-use syn::parse::{Parse, ParseStream, Result};
-use syn::spanned::Spanned;
-use syn::{
-    parse_quote, Error, Expr, FnArg, Ident, ImplItem, ImplItemMethod, ItemImpl,
-    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<AliasSrc>,
-}
-
-impl Parse for AliasArgs {
-    fn parse(input: ParseStream) -> Result<Self> {
-        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<Self> {
-        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<HashMap<Ident, Vec<AliasSrc>>> {
-    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::<Vec<_>>()
-            .into_iter();
-
-        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_fn<'a>(
-    function: &'a mut ImplItemMethod,
-    alias_map: &mut HashMap<Ident, Vec<AliasSrc>>,
-) -> Result<ParsedFn<'a>> {
-    let fn_name = function.sig.ident.clone();
-    // Get the name of the first (`input`) function argument
-    let input_arg = function.sig.inputs.first().ok_or_else(|| {
-        Error::new(
-            function.sig.inputs.span(),
-            "a rule function needs an `input` argument",
-        )
-    })?;
-    let input_arg = match &input_arg {
-        FnArg::Receiver(_) => return Err(Error::new(
-            input_arg.span(),
-            "a rule function should not have a `self` argument",
-        )),
-        FnArg::Typed(input_arg) => match &*input_arg.pat{
-            Pat::Ident(ident) => ident.ident.clone(),
-            _ => return Err(Error::new(
-                input_arg.span(),
-                "this argument should be a plain identifier instead of a pattern",
-            )),
-        }
-    };
-
-    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(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)]
-        #function
-    );
-
-    // `prec_climb` attr
-    let prec_climb_attrs: Vec<_> = function
-        .attrs
-        .drain_filter(|attr| attr.path.is_ident("prec_climb"))
-        .collect();
-
-    if prec_climb_attrs.len() > 1 {
-        return Err(Error::new(
-            prec_climb_attrs[1].span(),
-            "expected at most one prec_climb attribute",
-        ));
-    } else if prec_climb_attrs.is_empty() {
-        // do nothing
-    } else {
-        let attr = prec_climb_attrs.into_iter().next().unwrap();
-        let PrecClimbArgs {
-            child_rule,
-            climber,
-        } = attr.parse_args()?;
-
-        function.block = parse_quote!({
-            #function
-
-            #climber.climb(
-                #input_arg.pair.clone().into_inner(),
-                |p| Self::#child_rule(#input_arg.with_pair(p)),
-                |l, op, r| {
-                    #fn_name(#input_arg.clone(), l?, op, r?)
-                },
-            )
-        });
-        // Remove the 3 last arguments to keep only the `input` one
-        function.sig.inputs.pop();
-        function.sig.inputs.pop();
-        function.sig.inputs.pop();
-        // Check that an argument remains
-        function.sig.inputs.first().ok_or_else(|| {
-            Error::new(
-                function.sig.inputs.span(),
-                "a prec_climb function needs 4 arguments",
-            )
-        })?;
-    }
-
-    // `alias` attr
-    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 <Self as PestConsumer>::allows_shortcut(#input_arg.as_rule()) {
-                if let Some(child) = #input_arg.single_child() {
-                    if &<Self as PestConsumer>::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,
-                r => unreachable!(
-                    "make_parser: called {} on {:?}",
-                    stringify!(#fn_name),
-                    r
-                )
-            }
-        });
-    }
-
-    Ok(())
-}
-
-pub fn make_parser(
-    attrs: proc_macro::TokenStream,
-    input: proc_macro::TokenStream,
-) -> Result<proc_macro2::TokenStream> {
-    let rule_enum: Ident = syn::parse(attrs)?;
-    let mut imp: ItemImpl = syn::parse(input)?;
-
-    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))
-        .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::#ident => #is_shortcut,
-            )
-        })
-        .collect();
-
-    let fn_map: HashMap<Ident, ParsedFn> = imp
-        .items
-        .iter_mut()
-        .flat_map(|item| match item {
-            ImplItem::Method(m) => Some(m),
-            _ => None,
-        })
-        .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::<Result<_>>()?;
-
-    // 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, 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);
-
-            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 {}",
-                                stringify!(#tgt),
-                            ))),
-                        r => unreachable!(
-                            "make_parser: called {} on {:?}",
-                            stringify!(#tgt),
-                            r
-                        )
-                    }
-                }
-            ))
-        })
-        .collect::<Result<_>>()?;
-    imp.items.extend(extra_fns);
-
-    let ty = &imp.self_ty;
-    let (impl_generics, _, where_clause) = imp.generics.split_for_impl();
-    Ok(quote!(
-        impl #impl_generics PestConsumer for #ty #where_clause {
-            type Rule = #rule_enum;
-            fn rule_alias(rule: Self::Rule) -> String {
-                match rule {
-                    #(#rule_alias_branches)*
-                    r => format!("{:?}", r),
-                }
-            }
-            fn allows_shortcut(rule: Self::Rule) -> bool {
-                match rule {
-                    #(#shortcut_branches)*
-                    _ => false,
-                }
-            }
-        }
-
-        #imp
-    ))
-}
diff --git a/dhall_proc_macros/src/parse_children.rs b/dhall_proc_macros/src/parse_children.rs
deleted file mode 100644
index a35c03f..0000000
--- a/dhall_proc_macros/src/parse_children.rs
+++ /dev/null
@@ -1,215 +0,0 @@
-use proc_macro2::{Span, TokenStream};
-use quote::quote;
-use syn::parse::{Parse, ParseStream, Result};
-use syn::punctuated::Punctuated;
-use syn::spanned::Spanned;
-use syn::{bracketed, parenthesized, token, Error, Expr, Ident, Pat, Token};
-
-#[derive(Debug, Clone)]
-struct ChildrenBranch {
-    pattern_span: Span,
-    pattern: Punctuated<ChildrenBranchPatternItem, Token![,]>,
-    body: Expr,
-}
-
-#[derive(Debug, Clone)]
-enum ChildrenBranchPatternItem {
-    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 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 {
-            pattern_span,
-            pattern,
-            body,
-        })
-    }
-}
-
-impl Parse for ChildrenBranchPatternItem {
-    fn parse(input: ParseStream) -> Result<Self> {
-        let contents;
-        let rule_name = input.parse()?;
-        parenthesized!(contents in input);
-        if input.peek(Token![..]) {
-            let binder = contents.parse()?;
-            let _: Token![..] = input.parse()?;
-            Ok(ChildrenBranchPatternItem::Multiple { rule_name, binder })
-        } else if input.is_empty() || input.peek(Token![,]) {
-            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_parser_branch(
-    branch: &ChildrenBranch,
-    i_inputs: &Ident,
-) -> 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, 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!(stringify!(#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 == stringify!(#rule_name)
-                    )
-                };
-                all_match(#i_variable_pattern)
-            } &&
-        ),
-    });
-
-    // 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 = Self::#rule_name(
-                #i_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 = Self::#rule_name(
-                #i_inputs.next_back().unwrap()
-            )?;
-        ))
-    }
-    if let Some((rule_name, binder)) = multiple {
-        parses.push(quote!(
-            let #binder = #i_inputs
-                .map(|i| Self::#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 i_children_rules = Ident::new("___children_rules", Span::call_site());
-    let i_inputs = Ident::new("___inputs", Span::call_site());
-
-    let input_expr = &input.input_expr;
-    let branches = input
-        .branches
-        .iter()
-        .map(|br| make_parser_branch(br, &i_inputs))
-        .collect::<Result<Vec<_>>>()?;
-
-    Ok(quote!({
-        let #i_children_rules: Vec<_> = #input_expr.pair
-            .clone()
-            .into_inner()
-            .map(|p| p.as_rule())
-            .map(<Self as PestConsumer>::rule_alias)
-            .collect();
-        let #i_children_rules: Vec<&str> = #i_children_rules
-            .iter()
-            .map(String::as_str)
-            .collect();
-
-        #[allow(unused_mut)]
-        let mut #i_inputs = #input_expr
-            .pair
-            .clone()
-            .into_inner()
-            .map(|p| #input_expr.with_pair(p));
-
-        #[allow(unreachable_code)]
-        match #i_children_rules.as_slice() {
-            #(#branches,)*
-            [..] => return Err(#input_expr.error(
-                format!("Unexpected children: {:?}", #i_children_rules)
-            )),
-        }
-    }))
-}