From 66260f8e386f7a447352bd8ccbda064b00b698bc Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 13 Aug 2019 23:44:52 +0200
Subject: Implement inline headers parsing

---
 dhall_generated_parser/build.rs | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

(limited to 'dhall_generated_parser')

diff --git a/dhall_generated_parser/build.rs b/dhall_generated_parser/build.rs
index 5275097..070aa9c 100644
--- a/dhall_generated_parser/build.rs
+++ b/dhall_generated_parser/build.rs
@@ -26,16 +26,15 @@ fn main() -> std::io::Result<()> {
             rules.get_mut(&line[2..]).map(|x| x.silent = true);
         }
     }
-    rules.remove("http");
-    rules.remove("url_path");
-    rules.remove("simple_label");
-    rules.remove("nonreserved_label");
 
     let mut file = File::create(pest_path)?;
     writeln!(&mut file, "// AUTO-GENERATED FILE. See build.rs.")?;
-    writeln!(&mut file, "{}", render_rules_to_pest(rules).pretty(80))?;
 
-    writeln!(&mut file)?;
+    // TODO: this is a cheat; properly support RFC3986 URLs instead
+    rules.remove("url_path");
+    writeln!(&mut file, "url_path = _{{ path }}")?;
+
+    rules.remove("simple_label");
     writeln!(
         &mut file,
         "simple_label = {{
@@ -43,30 +42,23 @@ fn main() -> std::io::Result<()> {
             | !keyword ~ simple_label_first_char ~ simple_label_next_char*
     }}"
     )?;
-    // TODO: this is a cheat; actually implement inline headers instead
-    writeln!(
-        &mut file,
-        "http = {{
-            http_raw
-            ~ (whsp
-                ~ using
-                ~ whsp1
-                ~ (import_hashed | ^\"(\" ~ whsp ~ import_hashed ~ whsp ~ ^\")\"))?
-    }}"
-    )?;
-    // TODO: this is a cheat; properly support RFC3986 URLs instead
-    writeln!(&mut file, "url_path = _{{ path }}")?;
+
+    rules.remove("nonreserved_label");
     writeln!(
         &mut file,
         "nonreserved_label = _{{
             !(builtin ~ !simple_label_next_char) ~ label
     }}"
     )?;
+
     writeln!(
         &mut file,
         "final_expression = ${{ SOI ~ complete_expression ~ EOI }}"
     )?;
 
+    writeln!(&mut file)?;
+    writeln!(&mut file, "{}", render_rules_to_pest(rules).pretty(80))?;
+
     // Generate pest parser manually to avoid spurious recompilations
     let derived = {
         let pest_path = "dhall.pest";
-- 
cgit v1.3.1


From e4bdadabeda8ff8dbae0376f9d1c25478b8c8821 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Thu, 15 Aug 2019 15:33:53 +0200
Subject: Use precedence climbing to parse expressions with operators

This speeds up parsing around 30%
---
 dhall/build.rs                                   |   5 +-
 dhall_generated_parser/build.rs                  |  31 ++++
 dhall_generated_parser/src/dhall.pest.visibility |  10 +-
 dhall_syntax/src/parser.rs                       | 227 +++++++++++------------
 4 files changed, 147 insertions(+), 126 deletions(-)

(limited to 'dhall_generated_parser')

diff --git a/dhall/build.rs b/dhall/build.rs
index cbda288..2305208 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -91,8 +91,9 @@ fn main() -> std::io::Result<()> {
     let mut file = File::create(parser_tests_path)?;
 
     make_test_module(&mut file, "parse", "parser/", "Parser", |path| {
-        // Too slow in debug mode
-        path == "success/largeExpression"
+        false
+            // Too slow in debug mode
+            || path == "success/largeExpression"
             // TODO: projection by expression
             || path == "success/recordProjectionByExpression"
             || path == "success/RecordProjectionByType"
diff --git a/dhall_generated_parser/build.rs b/dhall_generated_parser/build.rs
index 070aa9c..c562fad 100644
--- a/dhall_generated_parser/build.rs
+++ b/dhall_generated_parser/build.rs
@@ -51,6 +51,37 @@ fn main() -> std::io::Result<()> {
     }}"
     )?;
 
+    // Setup grammar for precedence climbing
+    rules.remove("operator_expression");
+    writeln!(&mut file, r##"
+        import_alt = {{ "?" ~ whsp1 }}
+        bool_or = {{ "||" }}
+        natural_plus = {{ "+" ~ whsp1 }}
+        text_append = {{ "++" }}
+        list_append = {{ "#" }}
+        bool_and = {{ "&&" }}
+        natural_times = {{ "*" }}
+        bool_eq = {{ "==" }}
+        bool_ne = {{ "!=" }}
+
+        operator = _{{
+            equivalent |
+            bool_ne |
+            bool_eq |
+            natural_times |
+            combine_types |
+            prefer |
+            combine |
+            bool_and |
+            list_append |
+            text_append |
+            natural_plus |
+            bool_or |
+            import_alt
+        }}
+        operator_expression = {{ application_expression ~ (whsp ~ operator ~ whsp ~ application_expression)* }}
+    "##)?;
+
     writeln!(
         &mut file,
         "final_expression = ${{ SOI ~ complete_expression ~ EOI }}"
diff --git a/dhall_generated_parser/src/dhall.pest.visibility b/dhall_generated_parser/src/dhall.pest.visibility
index 6b4c974..6fa5e01 100644
--- a/dhall_generated_parser/src/dhall.pest.visibility
+++ b/dhall_generated_parser/src/dhall.pest.visibility
@@ -84,10 +84,10 @@ Location
 # Optional_fold
 # Optional_build
 # Text_show
-# combine
-# combine_types
-# equivalent
-# prefer
+combine
+combine_types
+equivalent
+prefer
 lambda
 forall
 arrow
@@ -144,7 +144,7 @@ expression
 annotated_expression
 let_binding
 empty_list_literal
-# operator_expression
+operator_expression
 import_alt_expression
 or_expression
 plus_expression
diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index 8ecd0ab..5b213d1 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -1,5 +1,6 @@
 use itertools::Itertools;
 use pest::iterators::Pair;
+use pest::prec_climber as pcl;
 use pest::Parser;
 use std::borrow::Cow;
 use std::rc::Rc;
@@ -219,7 +220,7 @@ macro_rules! make_parser {
     );
 }
 
-// Non-recursive implementation to avoid stack overflows
+// (Mostly) non-recursive implementation to avoid stack overflows
 fn do_parse<'a>(
     input: Rc<str>,
     initial_pair: Pair<'a, Rule>,
@@ -232,30 +233,122 @@ fn do_parse<'a>(
     let mut pairs_stack: Vec<StackFrame> =
         vec![Unprocessed(initial_pair.clone())];
     let mut values_stack: Vec<ParsedValue> = vec![];
+
+    let operators = {
+        use Rule::*;
+        // In order of precedence
+        vec![
+            import_alt,
+            bool_or,
+            natural_plus,
+            text_append,
+            list_append,
+            bool_and,
+            combine,
+            prefer,
+            combine_types,
+            natural_times,
+            bool_eq,
+            bool_ne,
+            equivalent,
+        ]
+    };
+    let rule_to_binop = {
+        use crate::BinOp::*;
+        use Rule::*;
+        |r| {
+            Some(match r {
+                import_alt => ImportAlt,
+                bool_or => BoolOr,
+                natural_plus => NaturalPlus,
+                text_append => TextAppend,
+                list_append => ListAppend,
+                bool_and => BoolAnd,
+                combine => RecursiveRecordMerge,
+                prefer => RightBiasedRecordMerge,
+                combine_types => RecursiveRecordTypeMerge,
+                natural_times => NaturalTimes,
+                bool_eq => BoolEQ,
+                bool_ne => BoolNE,
+                equivalent => Equivalence,
+                _ => return None,
+            })
+        }
+    };
+    let climber = pcl::PrecClimber::new(
+        operators
+            .into_iter()
+            .map(|op| pcl::Operator::new(op, pcl::Assoc::Left))
+            .collect(),
+    );
+
     while let Some(p) = pairs_stack.pop() {
         match p {
             Unprocessed(mut pair) => loop {
-                let mut pairs: Vec<_> = pair.clone().into_inner().collect();
-                let n_children = pairs.len();
-                if n_children == 1 && can_be_shortcutted(pair.as_rule()) {
-                    pair = pairs.pop().unwrap();
-                    continue;
+                if can_be_shortcutted(pair.as_rule()) {
+                    let mut i = pair.clone().into_inner();
+                    let first = i.next();
+                    let second = i.next();
+                    match (first, second) {
+                        // If pair has exactly one child, just go on parsing that child
+                        (Some(p), None) => {
+                            pair = p;
+                            continue;
+                        }
+                        // Otherwise parse normally
+                        _ => {}
+                    }
+                }
+
+                // Use precedence climbing to parse operator_expression
+                if pair.as_rule() == Rule::operator_expression {
+                    let val = climber.climb(
+                        pair.clone().into_inner(),
+                        |p| do_parse(input.clone(), p),
+                        |l, p, r| {
+                            let o = match rule_to_binop(p.as_rule()) {
+                                Some(o) => o,
+                                None => Err(custom_parse_error(
+                                    &pair,
+                                    format!(
+                                        "Rule {:?} isn't an operator",
+                                        p.as_rule()
+                                    ),
+                                ))?,
+                            };
+                            use ParsedValue::expression;
+                            match (l?, r?) {
+                                (expression(l), expression(r)) => {
+                                    Ok(expression(unspanned(BinOp(o, l, r))))
+                                }
+                                (l, r) => Err(custom_parse_error(
+                                    &pair,
+                                    format!(
+                                        "Unexpected children: {:?}",
+                                        [l, r]
+                                    ),
+                                ))?,
+                            }
+                        },
+                    )?;
+                    values_stack.push(val);
+                    break;
                 } else {
-                    pairs_stack.push(Processed(pair, n_children));
-                    pairs_stack
-                        .extend(pairs.into_iter().map(StackFrame::Unprocessed));
+                    let n_children = pair.clone().into_inner().count();
+                    pairs_stack.push(Processed(pair.clone(), n_children));
+                    // Push the unparsed children onto the stack
+                    pairs_stack.extend(pair.into_inner().map(Unprocessed));
                     break;
                 }
             },
             Processed(pair, n) => {
+                // Take as many values from the values stack as that pair had children. This
+                // means we get exactly the children of the pair, but now they are parsed.
                 let mut children: Vec<_> =
                     values_stack.split_off(values_stack.len() - n);
                 children.reverse();
-                let val = match parse_any(input.clone(), pair.clone(), children)
-                {
-                    Ok(v) => v,
-                    Err(msg) => Err(custom_parse_error(&pair, msg))?,
-                };
+                let val = parse_any(input.clone(), pair.clone(), children)
+                    .map_err(|msg| custom_parse_error(&pair, msg))?;
                 values_stack.push(val);
             }
         }
@@ -268,19 +361,7 @@ fn can_be_shortcutted(rule: Rule) -> bool {
     use Rule::*;
     match rule {
         expression
-        | import_alt_expression
-        | or_expression
-        | plus_expression
-        | text_append_expression
-        | list_append_expression
-        | and_expression
-        | combine_expression
-        | prefer_expression
-        | combine_types_expression
-        | times_expression
-        | equal_expression
-        | not_equal_expression
-        | equivalent_expression
+        | operator_expression
         | application_expression
         | first_application_expression
         | selector_expression
@@ -765,98 +846,6 @@ make_parser! {
     token_rule!(List<()>);
     token_rule!(Optional<()>);
 
-    rule!(import_alt_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::ImportAlt;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(or_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::BoolOr;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(plus_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::NaturalPlus;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(text_append_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::TextAppend;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(list_append_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::ListAppend;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(and_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::BoolAnd;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(combine_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::RecursiveRecordMerge;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(prefer_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::RightBiasedRecordMerge;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(combine_types_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::RecursiveRecordTypeMerge;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(times_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::NaturalTimes;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(equal_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::BoolEQ;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(not_equal_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::BoolNE;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-    rule!(equivalent_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
-            let o = crate::BinOp::Equivalence;
-            rest.fold(first, |acc, e| unspanned(BinOp(o, acc, e)))
-        },
-    ));
-
     rule!(annotated_expression<ParsedSubExpr> as expression; span; children!(
         [expression(e)] => e,
         [expression(e), expression(annot)] => {
-- 
cgit v1.3.1


From 8eb169713ea1220f2d515391c08d34509d75ab73 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 16 Aug 2019 10:34:10 +0200
Subject: Match on rules in parser instead of on ParsedValues

---
 dhall_generated_parser/src/dhall.pest.visibility |   2 +-
 dhall_syntax/src/lib.rs                          |   1 +
 dhall_syntax/src/parser.rs                       | 153 +++++++++++++++++++----
 3 files changed, 130 insertions(+), 26 deletions(-)

(limited to 'dhall_generated_parser')

diff --git a/dhall_generated_parser/src/dhall.pest.visibility b/dhall_generated_parser/src/dhall.pest.visibility
index 6fa5e01..8235735 100644
--- a/dhall_generated_parser/src/dhall.pest.visibility
+++ b/dhall_generated_parser/src/dhall.pest.visibility
@@ -106,7 +106,7 @@ unquoted_path_component
 quoted_path_component
 path_component
 path
-# local
+local
 parent_path
 here_path
 home_path
diff --git a/dhall_syntax/src/lib.rs b/dhall_syntax/src/lib.rs
index 4566e64..e4a6077 100644
--- a/dhall_syntax/src/lib.rs
+++ b/dhall_syntax/src/lib.rs
@@ -2,6 +2,7 @@
 #![feature(slice_patterns)]
 #![feature(try_blocks)]
 #![feature(never_type)]
+#![feature(bind_by_move_pattern_guards)]
 #![allow(
     clippy::many_single_char_names,
     clippy::should_implement_trait,
diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index bcaa00e..366103e 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -127,17 +127,75 @@ macro_rules! make_parser {
     (@filter, token_rule) => (true);
     (@filter, rule_group) => (false);
 
-    (@construct_climber,
-        ($map:expr),
+    (@child_pattern,
+        $varpat:ident,
+        ($($acc:tt)*),
+        [$variant:ident ($x:pat), $($rest:tt)*]
+    ) => (
+        make_parser!(@child_pattern,
+            $varpat,
+            ($($acc)* , Rule::$variant),
+            [$($rest)*]
+        )
+    );
+    (@child_pattern,
+        $varpat:ident,
+        ($($acc:tt)*),
+        [$variant:ident ($x:ident).., $($rest:tt)*]
+    ) => (
+        make_parser!(@child_pattern,
+            $varpat,
+            ($($acc)* , $varpat..),
+            [$($rest)*]
+        )
+    );
+    (@child_pattern,
+        $varpat:ident,
+        (, $($acc:tt)*), [$(,)*]
+    ) => ([$($acc)*]);
+    (@child_pattern,
+        $varpat:ident,
+        ($($acc:tt)*), [$(,)*]
+    ) => ([$($acc)*]);
+
+    (@child_filter,
+        $varpat:ident,
+        [$variant:ident ($x:pat), $($rest:tt)*]
+    ) => (
+        true &&
+        make_parser!(@child_filter, $varpat, [$($rest)*])
+    );
+    (@child_filter,
+        $varpat:ident,
+        [$variant:ident ($x:ident).., $($rest:tt)*]
+    ) => (
+        $varpat.iter().all(|r| r == &Rule::$variant) &&
+        make_parser!(@child_filter, $varpat, [$($rest)*])
+    );
+    (@child_filter, $varpat:ident, [$(,)*]) => (true);
+
+    (@rule_alias,
+        rule!( $name:ident<$o:ty>; $($args:tt)* )
+    ) => (
+        Rule::$name
+    );
+    (@rule_alias,
         rule!(
             $name:ident<$o:ty>
             as $group:ident;
-            prec_climb!( $climber:expr, $($_rest:tt)* )
+            $($args:tt)*
         )
     ) => ({
-        $map.insert(Rule::$name, $climber)
+        Rule::$group
     });
-    (@construct_climber, ($($things:tt)*), $($args:tt)*) => (());
+    (@rule_alias,
+        token_rule!($name:ident<$o:ty>)
+    ) => ({
+        Rule::$name
+    });
+    (@rule_alias, rule_group!( $name:ident<$o:ty> )) => (
+        unreachable!()
+    );
 
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
@@ -169,19 +227,43 @@ macro_rules! make_parser {
             .into_inner()
             .map(|p| parse_any($climbers, $input.clone(), p))
             .collect::<Result<_, _>>()?;
+        let children_rules: Vec<Rule> = $pair
+            .clone()
+            .into_inner()
+            .map(|p| p.as_rule())
+            .map(rule_alias)
+            .collect();
 
         #[allow(unreachable_code)]
         let res: Result<_, String> = try {
             #[allow(unused_imports)]
             use ParsedValue::*;
             let $span = Span::make($input, $pair.as_span());
+            #[allow(unused_mut)]
+            let mut iter = children.into_iter();
 
-            improved_slice_patterns::match_vec!(children;
-                $( [$($args)*] => $body, )*
-                [x..] => Err(
-                    format!("Unexpected children: {:?}", x.collect::<Vec<_>>())
-                )?,
-            ).map_err(|_| -> String { unreachable!() })?
+            match children_rules.as_slice() {
+                $(
+                    make_parser!(@child_pattern, x, (), [$($args)*,])
+                    if make_parser!(@child_filter, x, [$($args)*,])
+                    => {
+                        let ret =
+                            improved_slice_patterns::destructure_iter!(iter;
+                                [$($args)*] => $body
+                        );
+                        match ret {
+                            Some(x) => x,
+                            None => Err({
+                                format!("Unexpected children: {:?}", children_rules)
+                            })?
+                        }
+                    }
+                    ,
+                )*
+                [..] => Err({
+                    format!("Unexpected children: {:?}", children_rules)
+                })?,
+            }
         };
 
         let res = res.map_err(|msg| custom_parse_error(&$pair, msg))?;
@@ -252,6 +334,18 @@ macro_rules! make_parser {
         unreachable!()
     );
 
+    (@construct_climber,
+        ($map:expr),
+        rule!(
+            $name:ident<$o:ty>
+            as $group:ident;
+            prec_climb!( $climber:expr, $($_rest:tt)* )
+        )
+    ) => ({
+        $map.insert(Rule::$name, $climber)
+    });
+    (@construct_climber, ($($things:tt)*), $($args:tt)*) => (());
+
     ($( $submac:ident!( $name:ident<$o:ty> $($args:tt)* ); )*) => (
         #[allow(non_camel_case_types, dead_code, clippy::large_enum_variant)]
         #[derive(Debug)]
@@ -284,6 +378,19 @@ macro_rules! make_parser {
             )*
         }
 
+        fn rule_alias(r: Rule) -> Rule {
+            match r {
+                $(
+                    make_parser!(@pattern, $submac, $name)
+                    if make_parser!(@filter, $submac)
+                    => make_parser!(@rule_alias,
+                                    $submac!( $name<$o> $($args)* ))
+                    ,
+                )*
+                r => r,
+            }
+        }
+
         fn parse_any<'a>(
             climbers: &HashMap<Rule, PrecClimber<Rule>>,
             input: Rc<str>,
@@ -520,21 +627,15 @@ make_parser! {
             lines.last_mut().unwrap().push(c);
             lines
         },
-        [single_quote_char("\n"), single_quote_continue(lines)] => {
-            let mut lines = lines;
-            lines.push(vec![]);
-            lines
-        },
-        [single_quote_char("\r\n"), single_quote_continue(lines)] => {
-            let mut lines = lines;
-            lines.push(vec![]);
-            lines
-        },
         [single_quote_char(c), single_quote_continue(lines)] => {
-            // TODO: don't allocate for every char
-            let c = InterpolatedTextContents::Text(c.to_owned());
             let mut lines = lines;
-            lines.last_mut().unwrap().push(c);
+            if c == "\n" || c == "\r\n" {
+                lines.push(vec![]);
+            } else {
+                // TODO: don't allocate for every char
+                let c = InterpolatedTextContents::Text(c.to_owned());
+                lines.last_mut().unwrap().push(c);
+            }
             lines
         },
         [] => {
@@ -631,7 +732,9 @@ make_parser! {
         }
     ));
 
-    rule_group!(local<(FilePrefix, Vec<String>)>);
+    rule!(local<(FilePrefix, Vec<String>)>; children!(
+        [local(l)] => l
+    ));
 
     rule!(parent_path<(FilePrefix, Vec<String>)> as local; children!(
         [path(p)] => (FilePrefix::Parent, p)
-- 
cgit v1.3.1


From c13a100c36c3b54d76dba2207aa75fa6736ebadc Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 26 Aug 2019 23:18:11 +0200
Subject: Remove rule aliasing

---
 dhall_generated_parser/src/dhall.pest.visibility |   2 +-
 dhall_syntax/src/parser.rs                       | 200 +++++++++++------------
 tests_buffer                                     |   1 +
 3 files changed, 95 insertions(+), 108 deletions(-)

(limited to 'dhall_generated_parser')

diff --git a/dhall_generated_parser/src/dhall.pest.visibility b/dhall_generated_parser/src/dhall.pest.visibility
index 8235735..2ac7fe4 100644
--- a/dhall_generated_parser/src/dhall.pest.visibility
+++ b/dhall_generated_parser/src/dhall.pest.visibility
@@ -160,7 +160,7 @@ not_equal_expression
 equivalent_expression
 application_expression
 first_application_expression
-# import_expression
+import_expression
 selector_expression
 selector
 labels
diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index d11eb18..2debc8b 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -174,12 +174,11 @@ macro_rules! make_parser {
     );
     (@rule_alias,
         rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
+            $name:ident<$o:ty>;
             $($args:tt)*
         )
     ) => ({
-        Rule::$group
+        Rule::$name
     });
     (@rule_alias,
         token_rule!($name:ident<$o:ty>)
@@ -190,8 +189,7 @@ macro_rules! make_parser {
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
         rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
+            $name:ident<$o:ty>;
             $span:ident;
             captured_str!($x:pat) => $body:expr
         )
@@ -199,15 +197,14 @@ macro_rules! make_parser {
         let res: Result<_, String> = try {
             let $span = Span::make($input, $pair.as_span());
             let $x = $pair.as_str();
-            ParsedValue::$group($body)
+            ParsedValue::$name($body)
         };
         res.map_err(|msg| custom_parse_error(&$pair, msg))
     });
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
         rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
+            $name:ident<$o:ty>;
             $span:ident;
             children!( $( [$($args:tt)*] => $body:expr ),* $(,)* )
         )
@@ -257,27 +254,33 @@ macro_rules! make_parser {
         };
 
         let res = res.map_err(|msg| custom_parse_error(&$pair, msg))?;
-        Ok(ParsedValue::$group(res))
+        Ok(ParsedValue::$name(res))
     });
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
         rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
-            prec_climb!( $_climber:expr, $args:pat => $body:expr $(,)* )
+            $name:ident<$o:ty>;
+            prec_climb!($other_name:ident, $_climber:expr, $args:pat => $body:expr $(,)* )
         )
     ) => ({
-        let climber = $climbers.get(&Rule::$name).unwrap();
+        let climber = $climbers.get(&Rule::$name).expect(&format!("UUUU: {:?}", $climbers));
         climber.climb(
             $pair.clone().into_inner(),
-            |p| parse_any($climbers, $input.clone(), p),
+            |p| {
+                let parsed = parse_any($climbers, $input.clone(), p)?;
+                if let ParsedValue::$other_name(x) = parsed {
+                    Ok(ParsedValue::$name(x))
+                } else {
+                    unreachable!()
+                }
+            },
             |l, op, r| {
                 let (l, r) = (l?, r?);
                 let res: Result<_, String> = try {
                     #[allow(unused_imports)]
                     use ParsedValue::*;
                     match (l, op, r) {
-                        $args => ParsedValue::$group($body),
+                        $args => ParsedValue::$name($body),
                         children => Err(
                             format!("Unexpected children: {:?}", children)
                         )?,
@@ -289,26 +292,13 @@ macro_rules! make_parser {
     });
     (@body,
         ($($things:tt)*),
-        rule!( $name:ident<$o:ty>; $($args:tt)* )
-    ) => (
-        make_parser!(@body,
-            ($($things)*),
-            rule!( $name<$o> as $name; $($args)* )
-        )
-    );
-    (@body,
-        ($($things:tt)*),
-        rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
-            $($args:tt)*
+        rule!( $name:ident<$o:ty>; $($args:tt)*
         )
     ) => ({
         make_parser!(@body,
             ($($things)*),
             rule!(
-                $name<$o>
-                as $group;
+                $name<$o>;
                 _span;
                 $($args)*
             )
@@ -324,9 +314,8 @@ macro_rules! make_parser {
     (@construct_climber,
         ($map:expr),
         rule!(
-            $name:ident<$o:ty>
-            as $group:ident;
-            prec_climb!( $climber:expr, $($_rest:tt)* )
+            $name:ident<$o:ty>;
+            prec_climb!( $other_name:ident, $climber:expr, $($_rest:tt)* )
         )
     ) => ({
         $map.insert(Rule::$name, $climber)
@@ -379,27 +368,8 @@ macro_rules! make_parser {
         fn parse_any<'a>(
             climbers: &HashMap<Rule, PrecClimber<Rule>>,
             input: Rc<str>,
-            mut pair: Pair<'a, Rule>,
+            pair: Pair<'a, Rule>,
         ) -> ParseResult<ParsedValue<'a>> {
-            // Avoid parsing while the pair has exactly one child that can be returned as-is
-            loop {
-                if can_be_shortcutted(pair.as_rule()) {
-                    let mut i = pair.clone().into_inner();
-                    let first = i.next();
-                    let second = i.next();
-                    match (first, second) {
-                        // If pair has exactly one child, just go on parsing that child
-                        (Some(p), None) => {
-                            pair = p;
-                            continue;
-                        }
-                        // Otherwise parse normally
-                        _ => break,
-                    }
-                }
-                break;
-            }
-
             match pair.as_rule() {
                 $(
                     Rule::$name => Parsers::$name(climbers, input, pair),
@@ -418,20 +388,6 @@ fn do_parse<'a>(
     parse_any(&climbers, input, pair)
 }
 
-// List of rules that can be shortcutted if they have a single child
-fn can_be_shortcutted(rule: Rule) -> bool {
-    use Rule::*;
-    match rule {
-        expression
-        | operator_expression
-        | application_expression
-        | first_application_expression
-        | selector_expression
-        | annotated_expression => true,
-        _ => false,
-    }
-}
-
 // Trim the shared indent off of a vec of lines, as defined by the Dhall semantics of multiline
 // literals.
 fn trim_indent(lines: &mut Vec<ParsedText>) {
@@ -591,10 +547,10 @@ make_parser! {
     rule!(single_quote_char<&'a str>;
         captured_str!(s) => s
     );
-    rule!(escaped_quote_pair<&'a str> as single_quote_char;
+    rule!(escaped_quote_pair<&'a str>;
         captured_str!(_) => "''"
     );
-    rule!(escaped_interpolation<&'a str> as single_quote_char;
+    rule!(escaped_interpolation<&'a str>;
         captured_str!(_) => "${"
     );
     rule!(interpolation<ParsedSubExpr>; children!(
@@ -609,6 +565,20 @@ make_parser! {
             lines.last_mut().unwrap().push(c);
             lines
         },
+        [escaped_quote_pair(c), single_quote_continue(lines)] => {
+            let mut lines = lines;
+            // TODO: don't allocate for every char
+            let c = InterpolatedTextContents::Text(c.to_owned());
+            lines.last_mut().unwrap().push(c);
+            lines
+        },
+        [escaped_interpolation(c), single_quote_continue(lines)] => {
+            let mut lines = lines;
+            // TODO: don't allocate for every char
+            let c = InterpolatedTextContents::Text(c.to_owned());
+            lines.last_mut().unwrap().push(c);
+            lines
+        },
         [single_quote_char(c), single_quote_continue(lines)] => {
             let mut lines = lines;
             if c == "\n" || c == "\r\n" {
@@ -682,7 +652,7 @@ make_parser! {
         }
     );
 
-    rule!(identifier<ParsedSubExpr> as expression; span; children!(
+    rule!(identifier<ParsedSubExpr>; span; children!(
         [variable(v)] => {
             spanned(span, Var(v))
         },
@@ -715,19 +685,22 @@ make_parser! {
     ));
 
     rule!(local<(FilePrefix, Vec<String>)>; children!(
-        [local(l)] => l
+        [parent_path(l)] => l,
+        [here_path(l)] => l,
+        [home_path(l)] => l,
+        [absolute_path(l)] => l,
     ));
 
-    rule!(parent_path<(FilePrefix, Vec<String>)> as local; children!(
+    rule!(parent_path<(FilePrefix, Vec<String>)>; children!(
         [path(p)] => (FilePrefix::Parent, p)
     ));
-    rule!(here_path<(FilePrefix, Vec<String>)> as local; children!(
+    rule!(here_path<(FilePrefix, Vec<String>)>; children!(
         [path(p)] => (FilePrefix::Here, p)
     ));
-    rule!(home_path<(FilePrefix, Vec<String>)> as local; children!(
+    rule!(home_path<(FilePrefix, Vec<String>)>; children!(
         [path(p)] => (FilePrefix::Home, p)
     ));
-    rule!(absolute_path<(FilePrefix, Vec<String>)> as local; children!(
+    rule!(absolute_path<(FilePrefix, Vec<String>)>; children!(
         [path(p)] => (FilePrefix::Absolute, p)
     ));
 
@@ -760,7 +733,7 @@ make_parser! {
 
     rule!(http<URL<ParsedSubExpr>>; children!(
         [http_raw(url)] => url,
-        [http_raw(url), expression(e)] =>
+        [http_raw(url), import_expression(e)] =>
             URL { headers: Some(e), ..url },
     ));
 
@@ -828,7 +801,7 @@ make_parser! {
     token_rule!(Text<()>);
     token_rule!(Location<()>);
 
-    rule!(import<ParsedSubExpr> as expression; span; children!(
+    rule!(import<ParsedSubExpr>; span; children!(
         [import_hashed(imp)] => {
             spanned(span, Import(crate::Import {
                 mode: ImportMode::Code,
@@ -857,13 +830,13 @@ make_parser! {
     token_rule!(if_<()>);
     token_rule!(in_<()>);
 
-    rule!(empty_list_literal<ParsedSubExpr> as expression; span; children!(
-        [expression(e)] => {
+    rule!(empty_list_literal<ParsedSubExpr>; span; children!(
+        [application_expression(e)] => {
             spanned(span, EmptyListLit(e))
         },
     ));
 
-    rule!(expression<ParsedSubExpr> as expression; span; children!(
+    rule!(expression<ParsedSubExpr>; span; children!(
         [lambda(()), label(l), expression(typ),
                 arrow(()), expression(body)] => {
             spanned(span, Lam(l, typ, body))
@@ -881,16 +854,17 @@ make_parser! {
                 arrow(()), expression(body)] => {
             spanned(span, Pi(l, typ, body))
         },
-        [expression(typ), arrow(()), expression(body)] => {
+        [operator_expression(typ), arrow(()), expression(body)] => {
             spanned(span, Pi("_".into(), typ, body))
         },
-        [merge(()), expression(x), expression(y), expression(z)] => {
+        [merge(()), import_expression(x), import_expression(y), application_expression(z)] => {
             spanned(span, Merge(x, y, Some(z)))
         },
+        [empty_list_literal(e)] => e,
         [assert(()), expression(x)] => {
             spanned(span, Assert(x))
         },
-        [expression(e)] => e,
+        [annotated_expression(e)] => e,
     ));
 
     rule!(let_binding<(Label, Option<ParsedSubExpr>, ParsedSubExpr)>;
@@ -904,14 +878,14 @@ make_parser! {
     token_rule!(List<()>);
     token_rule!(Optional<()>);
 
-    rule!(annotated_expression<ParsedSubExpr> as expression; span; children!(
-        [expression(e)] => e,
-        [expression(e), expression(annot)] => {
+    rule!(annotated_expression<ParsedSubExpr>; span; children!(
+        [operator_expression(e)] => e,
+        [operator_expression(e), expression(annot)] => {
             spanned(span, Annot(e, annot))
         },
     ));
 
-    rule!(operator_expression<ParsedSubExpr> as expression; prec_climb!(
+    rule!(operator_expression<ParsedSubExpr>; prec_climb!(application_expression,
         {
             use Rule::*;
             // In order of precedence
@@ -937,7 +911,7 @@ make_parser! {
                     .collect(),
             )
         },
-        (expression(l), op, expression(r)) => {
+        (operator_expression(l), op, operator_expression(r)) => {
             use crate::BinOp::*;
             use Rule::*;
             let op = match op.as_rule() {
@@ -966,32 +940,38 @@ make_parser! {
     token_rule!(Some_<()>);
     token_rule!(toMap<()>);
 
-    rule!(application_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), expression(rest)..] => {
+    rule!(application_expression<ParsedSubExpr>; children!(
+        [first_application_expression(e)] => e,
+        [first_application_expression(first), import_expression(rest)..] => {
             rest.fold(first, |acc, e| unspanned(App(acc, e)))
         },
     ));
 
-    rule!(first_application_expression<ParsedSubExpr> as expression; span;
+    rule!(first_application_expression<ParsedSubExpr>; span;
             children!(
-        [expression(e)] => e,
-        [Some_(()), expression(e)] => {
+        [Some_(()), import_expression(e)] => {
             spanned(span, SomeLit(e))
         },
-        [merge(()), expression(x), expression(y)] => {
+        [merge(()), import_expression(x), import_expression(y)] => {
             spanned(span, Merge(x, y, None))
         },
+        [import_expression(e)] => e,
     ));
 
-    rule!(selector_expression<ParsedSubExpr> as expression; children!(
-        [expression(e)] => e,
-        [expression(first), selector(rest)..] => {
+    rule!(import_expression<ParsedSubExpr>; span;
+            children!(
+        [selector_expression(e)] => e,
+        [import(e)] => e,
+    ));
+
+    rule!(selector_expression<ParsedSubExpr>; children!(
+        [primitive_expression(e)] => e,
+        [primitive_expression(first), selector(rest)..] => {
             rest.fold(first, |acc, e| unspanned(match e {
                 Either::Left(l) => Field(acc, l),
                 Either::Right(ls) => Projection(acc, ls),
             }))
-        }
+        },
     ));
 
     rule!(selector<Either<Label, DupTreeSet<Label>>>; children!(
@@ -1004,24 +984,30 @@ make_parser! {
         [label(ls)..] => ls.collect(),
     ));
 
-    rule!(primitive_expression<ParsedSubExpr> as expression; span; children!(
+    rule!(primitive_expression<ParsedSubExpr>; span; children!(
         [double_literal(n)] => spanned(span, DoubleLit(n)),
         [natural_literal(n)] => spanned(span, NaturalLit(n)),
         [integer_literal(n)] => spanned(span, IntegerLit(n)),
         [double_quote_literal(s)] => spanned(span, TextLit(s)),
         [single_quote_literal(s)] => spanned(span, TextLit(s)),
+        [empty_record_type(e)] => e,
+        [empty_record_literal(e)] => e,
+        [non_empty_record_type_or_literal(e)] => e,
+        [union_type(e)] => e,
+        [non_empty_list_literal(e)] => e,
+        [identifier(e)] => e,
         [expression(e)] => e,
     ));
 
-    rule!(empty_record_literal<ParsedSubExpr> as expression; span;
+    rule!(empty_record_literal<ParsedSubExpr>; span;
         captured_str!(_) => spanned(span, RecordLit(Default::default()))
     );
 
-    rule!(empty_record_type<ParsedSubExpr> as expression; span;
+    rule!(empty_record_type<ParsedSubExpr>; span;
         captured_str!(_) => spanned(span, RecordType(Default::default()))
     );
 
-    rule!(non_empty_record_type_or_literal<ParsedSubExpr> as expression; span;
+    rule!(non_empty_record_type_or_literal<ParsedSubExpr>; span;
           children!(
         [label(first_label), non_empty_record_type(rest)] => {
             let (first_expr, mut map) = rest;
@@ -1057,7 +1043,7 @@ make_parser! {
         [label(name), expression(expr)] => (name, expr)
     ));
 
-    rule!(union_type<ParsedSubExpr> as expression; span; children!(
+    rule!(union_type<ParsedSubExpr>; span; children!(
         [empty_union_type(_)] => {
             spanned(span, UnionType(Default::default()))
         },
@@ -1073,7 +1059,7 @@ make_parser! {
         [label(name)] => (name, None),
     ));
 
-    rule!(non_empty_list_literal<ParsedSubExpr> as expression; span;
+    rule!(non_empty_list_literal<ParsedSubExpr>; span;
           children!(
         [expression(items)..] => spanned(
             span,
@@ -1081,7 +1067,7 @@ make_parser! {
         )
     ));
 
-    rule!(final_expression<ParsedSubExpr> as expression; children!(
+    rule!(final_expression<ParsedSubExpr>; children!(
         [expression(e), EOI(_eoi)] => e
     ));
 }
@@ -1092,7 +1078,7 @@ pub fn parse_expr(s: &str) -> ParseResult<ParsedSubExpr> {
     let expr = do_parse(rc_input, pairs.next().unwrap())?;
     assert_eq!(pairs.next(), None);
     match expr {
-        ParsedValue::expression(e) => Ok(e),
+        ParsedValue::final_expression(e) => Ok(e),
         _ => unreachable!(),
     }
 }
diff --git a/tests_buffer b/tests_buffer
index 1ad880e..67de9eb 100644
--- a/tests_buffer
+++ b/tests_buffer
@@ -9,6 +9,7 @@ success/
         PrecedenceAll2 a b != c == d * e ⩓ f ⫽ g ∧ h && i # j ++ k + l || m ? n
     LetNoAnnot let x = y in e
     LetAnnot let x: T = y in e
+    EmptyRecordLiteral {=}
 failure/
     AssertNoAnnotation assert
 
-- 
cgit v1.3.1


From 7b891800afa932660bc889e43c41c5d8f805cdc2 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 27 Aug 2019 13:42:53 +0200
Subject: Rework parse macros to avoid the large ParsedValue enum

---
 Cargo.lock                                       |   1 -
 dhall_generated_parser/src/dhall.pest.visibility |   2 +-
 dhall_syntax/Cargo.toml                          |   1 -
 dhall_syntax/src/parser.rs                       | 285 +++++++++++------------
 4 files changed, 140 insertions(+), 149 deletions(-)

(limited to 'dhall_generated_parser')

diff --git a/Cargo.lock b/Cargo.lock
index c073fad..f754891 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -107,7 +107,6 @@ dependencies = [
  "dhall_generated_parser 0.1.0",
  "either 1.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "improved_slice_patterns 2.0.0",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "percent-encoding 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "pest 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/dhall_generated_parser/src/dhall.pest.visibility b/dhall_generated_parser/src/dhall.pest.visibility
index 2ac7fe4..dcebf45 100644
--- a/dhall_generated_parser/src/dhall.pest.visibility
+++ b/dhall_generated_parser/src/dhall.pest.visibility
@@ -141,7 +141,7 @@ hash
 import_hashed
 import
 expression
-annotated_expression
+# annotated_expression
 let_binding
 empty_list_literal
 operator_expression
diff --git a/dhall_syntax/Cargo.toml b/dhall_syntax/Cargo.toml
index 6a61b09..08d0195 100644
--- a/dhall_syntax/Cargo.toml
+++ b/dhall_syntax/Cargo.toml
@@ -16,4 +16,3 @@ either = "1.5.2"
 take_mut = "0.2.2"
 hex = "0.3.2"
 dhall_generated_parser = { path = "../dhall_generated_parser" }
-improved_slice_patterns = { version = "2.0.0", path = "../improved_slice_patterns" }
diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index 2debc8b..8facb3e 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -119,6 +119,76 @@ fn debug_pair(pair: Pair<Rule>) -> String {
     s
 }
 
+macro_rules! parse_children {
+    // Variable length pattern with a common unary variant
+    (@match_forwards,
+        $parse_args:expr,
+        $iter:expr,
+        ($body:expr),
+        $variant:ident ($x:ident)..,
+        $($rest:tt)*
+    ) => {
+        parse_children!(@match_backwards,
+            $parse_args, $iter,
+            ({
+                let $x = $iter
+                    .map(|x| Parsers::$variant($parse_args, x))
+                    .collect::<Result<Vec<_>, _>>()?
+                    .into_iter();
+                $body
+            }),
+            $($rest)*
+        )
+    };
+    // Single item pattern
+    (@match_forwards,
+        $parse_args:expr,
+        $iter:expr,
+        ($body:expr),
+        $variant:ident ($x:pat),
+        $($rest:tt)*
+    ) => {{
+        let p = $iter.next().unwrap();
+        let $x = Parsers::$variant($parse_args, p)?;
+        parse_children!(@match_forwards,
+            $parse_args, $iter,
+            ($body),
+            $($rest)*
+        )
+    }};
+    // Single item pattern after a variable length one: declare reversed and take from the end
+    (@match_backwards,
+        $parse_args:expr,
+        $iter:expr,
+        ($body:expr),
+        $variant:ident ($x:pat),
+        $($rest:tt)*
+    ) => {
+        parse_children!(@match_backwards, $parse_args, $iter, ({
+            let p = $iter.next_back().unwrap();
+            let $x = Parsers::$variant($parse_args, p)?;
+            $body
+        }), $($rest)*)
+    };
+
+    // Check no elements remain
+    (@match_forwards, $parse_args:expr, $iter:expr, ($body:expr) $(,)*) => {
+        $body
+    };
+    // After a variable length pattern, everything has already been consumed
+    (@match_backwards, $parse_args:expr, $iter:expr, ($body:expr) $(,)*) => {
+        $body
+    };
+
+    ($parse_args:expr, $iter:expr; [$($args:tt)*] => $body:expr) => {
+        parse_children!(@match_forwards,
+            $parse_args, $iter,
+            ($body),
+            $($args)*,
+        )
+    };
+}
+
 macro_rules! make_parser {
     (@children_pattern,
         $varpat:ident,
@@ -155,7 +225,6 @@ macro_rules! make_parser {
         $varpat:ident,
         [$variant:ident ($x:pat), $($rest:tt)*]
     ) => (
-        true &&
         make_parser!(@children_filter, $varpat, [$($rest)*])
     );
     (@children_filter,
@@ -167,25 +236,6 @@ macro_rules! make_parser {
     );
     (@children_filter, $varpat:ident, [$(,)*]) => (true);
 
-    (@rule_alias,
-        rule!( $name:ident<$o:ty>; $($args:tt)* )
-    ) => (
-        Rule::$name
-    );
-    (@rule_alias,
-        rule!(
-            $name:ident<$o:ty>;
-            $($args:tt)*
-        )
-    ) => ({
-        Rule::$name
-    });
-    (@rule_alias,
-        token_rule!($name:ident<$o:ty>)
-    ) => ({
-        Rule::$name
-    });
-
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
         rule!(
@@ -194,11 +244,9 @@ macro_rules! make_parser {
             captured_str!($x:pat) => $body:expr
         )
     ) => ({
-        let res: Result<_, String> = try {
-            let $span = Span::make($input, $pair.as_span());
-            let $x = $pair.as_str();
-            ParsedValue::$name($body)
-        };
+        let $span = Span::make($input.clone(), $pair.as_span());
+        let $x = $pair.as_str();
+        let res: Result<_, String> = try { $body };
         res.map_err(|msg| custom_parse_error(&$pair, msg))
     });
     (@body,
@@ -209,90 +257,64 @@ macro_rules! make_parser {
             children!( $( [$($args:tt)*] => $body:expr ),* $(,)* )
         )
     ) => ({
-        let children: Vec<_> = $pair
-            .clone()
-            .into_inner()
-            .map(|p| parse_any($climbers, $input.clone(), p))
-            .collect::<Result<_, _>>()?;
         let children_rules: Vec<Rule> = $pair
             .clone()
             .into_inner()
             .map(|p| p.as_rule())
-            .map(rule_alias)
             .collect();
 
+        let $span = Span::make($input.clone(), $pair.as_span());
+        #[allow(unused_mut)]
+        let mut iter = $pair.clone().into_inner();
+
         #[allow(unreachable_code)]
-        let res: Result<_, String> = try {
-            #[allow(unused_imports)]
-            use ParsedValue::*;
-            let $span = Span::make($input, $pair.as_span());
-            #[allow(unused_mut)]
-            let mut iter = children.into_iter();
-
-            match children_rules.as_slice() {
-                $(
-                    make_parser!(@children_pattern, x, (), [$($args)*,])
-                    if make_parser!(@children_filter, x, [$($args)*,])
-                    => {
-                        let ret =
-                            improved_slice_patterns::destructure_iter!(iter;
-                                [$($args)*] => $body
-                        );
-                        match ret {
-                            Some(x) => x,
-                            None => Err({
-                                format!("Unexpected children: {:?}", children_rules)
-                            })?
+        match children_rules.as_slice() {
+            $(
+                make_parser!(@children_pattern, x, (), [$($args)*,])
+                if make_parser!(@children_filter, x, [$($args)*,])
+                => {
+                    parse_children!(($climbers, $input.clone()), iter;
+                        [$($args)*] => {
+                            let res: Result<_, String> = try { $body };
+                            res.map_err(|msg| custom_parse_error(&$pair, msg))
                         }
-                    }
-                    ,
-                )*
-                [..] => Err({
-                    format!("Unexpected children: {:?}", children_rules)
-                })?,
-            }
-        };
-
-        let res = res.map_err(|msg| custom_parse_error(&$pair, msg))?;
-        Ok(ParsedValue::$name(res))
+                    )
+                }
+                ,
+            )*
+            [..] => Err(custom_parse_error(
+                &$pair,
+                format!("Unexpected children: {:?}", children_rules)
+            )),
+        }
     });
     (@body,
         ($climbers:expr, $input:expr, $pair:expr),
         rule!(
             $name:ident<$o:ty>;
-            prec_climb!($other_name:ident, $_climber:expr, $args:pat => $body:expr $(,)* )
+            prec_climb!(
+                $other_rule:ident,
+                $_climber:expr,
+                $args:pat => $body:expr $(,)*
+            )
         )
     ) => ({
-        let climber = $climbers.get(&Rule::$name).expect(&format!("UUUU: {:?}", $climbers));
+        let climber = $climbers.get(&Rule::$name).unwrap();
         climber.climb(
             $pair.clone().into_inner(),
-            |p| {
-                let parsed = parse_any($climbers, $input.clone(), p)?;
-                if let ParsedValue::$other_name(x) = parsed {
-                    Ok(ParsedValue::$name(x))
-                } else {
-                    unreachable!()
-                }
-            },
+            |p| Parsers::$other_rule(($climbers, $input.clone()), p),
             |l, op, r| {
-                let (l, r) = (l?, r?);
-                let res: Result<_, String> = try {
-                    #[allow(unused_imports)]
-                    use ParsedValue::*;
-                    match (l, op, r) {
-                        $args => ParsedValue::$name($body),
-                        children => Err(
-                            format!("Unexpected children: {:?}", children)
-                        )?,
-                    }
-                };
+                let $args = (l?, op, r?);
+                let res: Result<_, String> = try { $body };
                 res.map_err(|msg| custom_parse_error(&$pair, msg))
             },
         )
     });
     (@body,
         ($($things:tt)*),
-        rule!( $name:ident<$o:ty>; $($args:tt)*
+        rule!(
+            $name:ident<$o:ty>;
+            $($args:tt)*
         )
     ) => ({
         make_parser!(@body,
@@ -308,14 +330,14 @@ macro_rules! make_parser {
         ($($things:tt)*),
         token_rule!($name:ident<$o:ty>)
     ) => ({
-        Ok(ParsedValue::$name(()))
+        Ok(())
     });
 
     (@construct_climber,
         ($map:expr),
         rule!(
             $name:ident<$o:ty>;
-            prec_climb!( $other_name:ident, $climber:expr, $($_rest:tt)* )
+            prec_climb!($other_rule:ident, $climber:expr, $($_rest:tt)* )
         )
     ) => ({
         $map.insert(Rule::$name, $climber)
@@ -323,10 +345,19 @@ macro_rules! make_parser {
     (@construct_climber, ($($things:tt)*), $($args:tt)*) => (());
 
     ($( $submac:ident!( $name:ident<$o:ty> $($args:tt)* ); )*) => (
-        #[allow(non_camel_case_types, dead_code, clippy::large_enum_variant)]
-        #[derive(Debug)]
-        enum ParsedValue<'a> {
-            $( $name($o), )*
+        struct Parsers;
+
+        impl Parsers {
+            $(
+            #[allow(non_snake_case, unused_variables)]
+            fn $name<'a>(
+                (climbers, input): (&HashMap<Rule, PrecClimber<Rule>>, Rc<str>),
+                pair: Pair<'a, Rule>,
+            ) -> ParseResult<$o> {
+                make_parser!(@body, (climbers, input, pair),
+                               $submac!( $name<$o> $($args)* ))
+            }
+            )*
         }
 
         fn construct_precclimbers() -> HashMap<Rule, PrecClimber<Rule>> {
@@ -338,56 +369,23 @@ macro_rules! make_parser {
             map
         }
 
-        struct Parsers;
+        struct EntryPoint;
 
-        impl Parsers {
+        impl EntryPoint {
             $(
-            #[allow(non_snake_case, unused_variables)]
+            #[allow(non_snake_case, dead_code)]
             fn $name<'a>(
-                climbers: &HashMap<Rule, PrecClimber<Rule>>,
                 input: Rc<str>,
                 pair: Pair<'a, Rule>,
-            ) -> ParseResult<ParsedValue<'a>> {
-                make_parser!(@body, (climbers, input, pair),
-                               $submac!( $name<$o> $($args)* ))
+            ) -> ParseResult<$o> {
+                let climbers = construct_precclimbers();
+                Parsers::$name((&climbers, input), pair)
             }
             )*
         }
-
-        fn rule_alias(r: Rule) -> Rule {
-            match r {
-                $(
-                    Rule::$name => {
-                        make_parser!(@rule_alias, $submac!($name<$o> $($args)*))
-                    }
-                )*
-                r => r,
-            }
-        }
-
-        fn parse_any<'a>(
-            climbers: &HashMap<Rule, PrecClimber<Rule>>,
-            input: Rc<str>,
-            pair: Pair<'a, Rule>,
-        ) -> ParseResult<ParsedValue<'a>> {
-            match pair.as_rule() {
-                $(
-                    Rule::$name => Parsers::$name(climbers, input, pair),
-                )*
-                r => Err(custom_parse_error(&pair, format!("Unexpected {:?}", r))),
-            }
-        }
     );
 }
 
-fn do_parse<'a>(
-    input: Rc<str>,
-    pair: Pair<'a, Rule>,
-) -> ParseResult<ParsedValue<'a>> {
-    let climbers = construct_precclimbers();
-    parse_any(&climbers, input, pair)
-}
-
 // Trim the shared indent off of a vec of lines, as defined by the Dhall semantics of multiline
 // literals.
 fn trim_indent(lines: &mut Vec<ParsedText>) {
@@ -857,14 +855,18 @@ make_parser! {
         [operator_expression(typ), arrow(()), expression(body)] => {
             spanned(span, Pi("_".into(), typ, body))
         },
-        [merge(()), import_expression(x), import_expression(y), application_expression(z)] => {
+        [merge(()), import_expression(x), import_expression(y),
+                application_expression(z)] => {
             spanned(span, Merge(x, y, Some(z)))
         },
         [empty_list_literal(e)] => e,
         [assert(()), expression(x)] => {
             spanned(span, Assert(x))
         },
-        [annotated_expression(e)] => e,
+        [operator_expression(e)] => e,
+        [operator_expression(e), expression(annot)] => {
+            spanned(span, Annot(e, annot))
+        },
     ));
 
     rule!(let_binding<(Label, Option<ParsedSubExpr>, ParsedSubExpr)>;
@@ -878,14 +880,8 @@ make_parser! {
     token_rule!(List<()>);
     token_rule!(Optional<()>);
 
-    rule!(annotated_expression<ParsedSubExpr>; span; children!(
-        [operator_expression(e)] => e,
-        [operator_expression(e), expression(annot)] => {
-            spanned(span, Annot(e, annot))
-        },
-    ));
-
-    rule!(operator_expression<ParsedSubExpr>; prec_climb!(application_expression,
+    rule!(operator_expression<ParsedSubExpr>; prec_climb!(
+        application_expression,
         {
             use Rule::*;
             // In order of precedence
@@ -911,7 +907,7 @@ make_parser! {
                     .collect(),
             )
         },
-        (operator_expression(l), op, operator_expression(r)) => {
+        (l, op, r) => {
             use crate::BinOp::*;
             use Rule::*;
             let op = match op.as_rule() {
@@ -1075,10 +1071,7 @@ make_parser! {
 pub fn parse_expr(s: &str) -> ParseResult<ParsedSubExpr> {
     let mut pairs = DhallParser::parse(Rule::final_expression, s)?;
     let rc_input = s.to_string().into();
-    let expr = do_parse(rc_input, pairs.next().unwrap())?;
+    let expr = EntryPoint::final_expression(rc_input, pairs.next().unwrap())?;
     assert_eq!(pairs.next(), None);
-    match expr {
-        ParsedValue::final_expression(e) => Ok(e),
-        _ => unreachable!(),
-    }
+    Ok(expr)
 }
-- 
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