From 9f41dc5a4680cba3697c64da28855c8d4f437191 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 10 Sep 2019 14:51:37 +0200
Subject: Implement parsing in PestConsumer

---
 dhall_syntax/src/parser.rs             | 14 +++++++-------
 pest_consume/src/lib.rs                | 23 +++++++++++++++++++++++
 pest_consume_macros/src/make_parser.rs | 19 ++++++++++++++++++-
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index a83b8d0..a783f77 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -2,11 +2,10 @@ use itertools::Itertools;
 use pest::iterators::Pair;
 use pest::prec_climber as pcl;
 use pest::prec_climber::PrecClimber;
-use pest::Parser;
 use std::rc::Rc;
 
 use dhall_generated_parser::{DhallParser, Rule};
-use pest_consume::{make_parser, match_inputs};
+use pest_consume::{make_parser, match_inputs, PestConsumer};
 
 use crate::map::{DupTreeMap, DupTreeSet};
 use crate::ExprF::*;
@@ -21,8 +20,6 @@ type ParsedText<E> = InterpolatedText<Expr<E>>;
 type ParsedTextContents<E> = InterpolatedTextContents<Expr<E>>;
 type ParseInput<'input, 'data> =
     pest_consume::ParseInput<'input, 'data, Rule, Rc<str>>;
-type ParseInputs<'input, 'data> =
-    pest_consume::ParseInputs<'input, 'data, Rule, Rc<str>>;
 
 pub type ParseError = pest::error::Error<Rule>;
 pub type ParseResult<T> = Result<T, ParseError>;
@@ -152,13 +149,16 @@ lazy_static::lazy_static! {
 
 struct Parsers;
 
-#[make_parser(Rule)]
+#[make_parser(DhallParser, Rule)]
 impl Parsers {
     #[entrypoint]
     fn entrypoint<E: Clone>(input_str: &str) -> ParseResult<Expr<E>> {
-        let pairs = DhallParser::parse(Rule::final_expression, input_str)?;
         let rc_input_str = input_str.to_string().into();
-        let inputs = ParseInputs::new(input_str, pairs, &rc_input_str);
+        let inputs = Self::parse_with_userdata(
+            Rule::final_expression,
+            input_str,
+            &rc_input_str,
+        )?;
         Ok(match_inputs!(inputs;
             [expression(e)] => e,
         ))
diff --git a/pest_consume/src/lib.rs b/pest_consume/src/lib.rs
index 8f882a9..1579f81 100644
--- a/pest_consume/src/lib.rs
+++ b/pest_consume/src/lib.rs
@@ -1,9 +1,12 @@
 use pest::error::{Error, ErrorVariant};
 use pest::iterators::{Pair, Pairs};
+use pest::Parser as PestParser;
 use pest::{RuleType, Span};
 
 pub use pest_consume_macros::{make_parser, match_inputs};
 
+static UNIT: () = ();
+
 /// Carries a pest Pair alongside custom user data.
 #[derive(Debug)]
 pub struct ParseInput<'input, 'data, Rule: RuleType, Data> {
@@ -76,6 +79,7 @@ impl<'i, 'd, R: RuleType, D> ParseInput<'i, 'd, R, D> {
     pub fn as_rule_alias<C>(&self) -> String
     where
         C: PestConsumer<Rule = R>,
+        <C as PestConsumer>::Parser: PestParser<R>,
     {
         C::rule_alias(self.as_rule())
     }
@@ -101,6 +105,7 @@ impl<'i, 'd, R: RuleType, D> ParseInputs<'i, 'd, R, D> {
     pub fn aliased_rules<C>(&self) -> Vec<String>
     where
         C: PestConsumer<Rule = R>,
+        <C as PestConsumer>::Parser: PestParser<R>,
     {
         self.clone().map(|p| p.as_rule_alias::<C>()).collect()
     }
@@ -113,8 +118,26 @@ impl<'i, 'd, R: RuleType, D> ParseInputs<'i, 'd, R, D> {
 /// Used by the macros.
 pub trait PestConsumer {
     type Rule: RuleType;
+    type Parser: PestParser<Self::Rule>;
     fn rule_alias(rule: Self::Rule) -> String;
     fn allows_shortcut(rule: Self::Rule) -> bool;
+
+    fn parse_with_userdata<'i, 'd, D>(
+        rule: Self::Rule,
+        input_str: &'i str,
+        user_data: &'d D,
+    ) -> Result<ParseInputs<'i, 'd, Self::Rule, D>, Error<Self::Rule>> {
+        let pairs = Self::Parser::parse(rule, input_str)?;
+        Ok(ParseInputs::new(input_str, pairs, user_data))
+    }
+
+    fn parse<'i>(
+        rule: Self::Rule,
+        input_str: &'i str,
+    ) -> Result<ParseInputs<'i, 'static, Self::Rule, ()>, Error<Self::Rule>>
+    {
+        Self::parse_with_userdata(rule, input_str, &UNIT)
+    }
 }
 
 impl<'i, 'd, R: RuleType, D> Iterator for ParseInputs<'i, 'd, R, D> {
diff --git a/pest_consume_macros/src/make_parser.rs b/pest_consume_macros/src/make_parser.rs
index 9de2f6f..0638c19 100644
--- a/pest_consume_macros/src/make_parser.rs
+++ b/pest_consume_macros/src/make_parser.rs
@@ -13,6 +13,11 @@ mod kw {
     syn::custom_keyword!(shortcut);
 }
 
+struct MakeParserAttrs {
+    parser: Ident,
+    rule_enum: Ident,
+}
+
 struct AliasArgs {
     target: Ident,
     is_shortcut: bool,
@@ -39,6 +44,15 @@ struct ParsedFn<'a> {
     alias_srcs: Vec<AliasSrc>,
 }
 
+impl Parse for MakeParserAttrs {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let parser = input.parse()?;
+        let _: Token![,] = input.parse()?;
+        let rule_enum = input.parse()?;
+        Ok(MakeParserAttrs { parser, rule_enum })
+    }
+}
+
 impl Parse for AliasArgs {
     fn parse(input: ParseStream) -> Result<Self> {
         let target = input.parse()?;
@@ -244,7 +258,9 @@ pub fn make_parser(
     attrs: proc_macro::TokenStream,
     input: proc_macro::TokenStream,
 ) -> Result<proc_macro2::TokenStream> {
-    let rule_enum: Ident = syn::parse(attrs)?;
+    let attrs: MakeParserAttrs = syn::parse(attrs)?;
+    let parser = &attrs.parser;
+    let rule_enum = &attrs.rule_enum;
     let mut imp: ItemImpl = syn::parse(input)?;
 
     let mut alias_map = collect_aliases(&mut imp)?;
@@ -322,6 +338,7 @@ pub fn make_parser(
     Ok(quote!(
         impl #impl_generics pest_consume::PestConsumer for #ty #where_clause {
             type Rule = #rule_enum;
+            type Parser = #parser;
             fn rule_alias(rule: Self::Rule) -> String {
                 match rule {
                     #(#rule_alias_branches)*
-- 
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