add AnnotatedBody in AST enum type

compiler/parse/src/ast.rs

@@ -277,6 +277,14 @@ pub enum Def<'a> {
     // No need to track that relationship in any data structure.
     Body(&'a Loc<Pattern<'a>>, &'a Loc<Expr<'a>>),
 
+    AnnotatedBody {
+        ann_pattern: Loc<Pattern<'a>>,
+        ann_type: Loc<TypeAnnotation<'a>>,
+        comment: Option<&'a str>,
+        body_pattern: Loc<Pattern<'a>>,
+        body_expr: Loc<Expr<'a>>,
+    },
+
     // Blank Space (e.g. comments, spaces, newlines) before or after a def.
     // We preserve this for the formatter; canonicalization ignores it.
     SpaceBefore(&'a Def<'a>, &'a [CommentOrNewline<'a>]),
@@ -668,6 +676,7 @@ impl<'a> Spaceable<'a> for Def<'a> {
 /// "currently attempting to parse a list." This helps error messages!
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Attempting {
+    LineComment,
     List,
     Keyword,
     StrLiteral,

compiler/parse/src/blankspace.rs

@@ -1,7 +1,8 @@
 use crate::ast::CommentOrNewline::{self, *};
-use crate::ast::Spaceable;
+use crate::ast::{Attempting, Spaceable};
 use crate::parser::{
-    self, and, peek_utf8_char, unexpected, unexpected_eof, FailReason, Parser, State,
+    self, and, ascii_char, ascii_string, optional, parse_utf8, peek_utf8_char, then, unexpected,
+    unexpected_eof, FailReason, Parser, State,
 };
 use bumpalo::collections::string::String;
 use bumpalo::collections::vec::Vec;
@@ -211,6 +212,33 @@ enum LineState {
     DocComment,
 }
 
+pub fn line_comment<'a>() -> impl Parser<'a, &'a str> {
+    then(
+        and!(ascii_char('#'), optional(ascii_string("# "))),
+        |_arena: &'a Bump, state: State<'a>, (_, opt_doc)| {
+            if opt_doc != None {
+                return Err(unexpected(3, state, Attempting::LineComment));
+            }
+            let mut length = 0;
+
+            for &byte in state.bytes.iter() {
+                if byte != b'\n' {
+                    length += 1;
+                } else {
+                    break;
+                }
+            }
+
+            let comment = &state.bytes[..length];
+            let state = state.advance_without_indenting(length + 1)?;
+            match parse_utf8(comment) {
+                Ok(comment_str) => Ok((comment_str, state)),
+                Err(reason) => state.fail(reason),
+            }
+        },
+    )
+}
+
 #[inline(always)]
 fn spaces<'a>(
     require_at_least_one: bool,

compiler/parse/src/expr.rs

@@ -2,7 +2,8 @@ use crate::ast::{
     AssignedField, Attempting, CommentOrNewline, Def, Expr, Pattern, Spaceable, TypeAnnotation,
 };
 use crate::blankspace::{
-    space0, space0_after, space0_around, space0_before, space1, space1_around, space1_before,
+    line_comment, space0, space0_after, space0_around, space0_before, space1, space1_around,
+    space1_before,
 };
 use crate::ident::{global_tag_or_ident, ident, lowercase_ident, Ident};
 use crate::keyword;
@@ -497,35 +498,66 @@ pub fn def<'a>(min_indent: u16) -> impl Parser<'a, Def<'a>> {
     // Indented more beyond the original indent.
     let indented_more = min_indent + 1;
 
-    // Constant or annotation
-    map_with_arena!(
-        and!(
-            // A pattern followed by '=' or ':'
-            space0_after(loc_closure_param(min_indent), min_indent),
-            either!(
-                // Constant
-                skip_first!(
-                    equals_for_def(),
-                    // Spaces after the '=' (at a normal indentation level) and then the expr.
-                    // The expr itself must be indented more than the pattern and '='
-                    space0_before(
-                        loc!(move |arena, state| parse_expr(indented_more, arena, state)),
-                        min_indent,
-                    )
-                ),
-                // Annotation
-                skip_first!(
-                    ascii_char(b':'),
-                    // Spaces after the ':' (at a normal indentation level) and then the type.
-                    // The type itself must be indented more than the pattern and ':'
-                    space0_before(type_annotation::located(indented_more), indented_more)
-                )
+    let pattern = space0_after(loc_closure_param(min_indent), min_indent);
+
+    let annotation = and!(
+        pattern,
+        skip_first!(
+            ascii_char(b':'),
+            // Spaces after the ':' (at a normal indentation level) and then the type.
+            // The type itself must be indented more than the pattern and ':'
+            space0_before(type_annotation::located(indented_more), indented_more)
+        )
+    );
+
+    let body = and!(
+        pattern,
+        skip_first!(
+            equals_for_def(),
+            // Spaces after the '=' (at a normal indentation level) and then the expr.
+            // The expr itself must be indented more than the pattern and '='
+            space0_before(
+                loc!(move |arena, state| parse_expr(indented_more, arena, state)),
+                min_indent,
             )
-        ),
-        |arena: &'a Bump, (loc_pattern, expr_or_ann)| match expr_or_ann {
-            Either::First(loc_expr) => Def::Body(arena.alloc(loc_pattern), arena.alloc(loc_expr)),
-            Either::Second(loc_ann) =>
-                annotation_or_alias(arena, &loc_pattern.value, loc_pattern.region, loc_ann),
+        )
+    );
+
+    let comment_or_newline = map!(
+        either!(ascii_char('\n'), line_comment()),
+        |either_comment_or_newline| match either_comment_or_newline {
+            Either::First(_) => None,
+            Either::Second(comment) => Some(comment),
+        }
+    );
+    let spaces_then_comment_or_newline: dyn Parser<'a, Option<&'a str>> =
+        skip_first!(zero_or_more!(ascii_char(' ')), comment_or_newline);
+    let annotated_body = and!(
+        annotation,
+        optional(and!(spaces_then_comment_or_newline, body))
+    );
+
+    map_with_arena!(
+        either!(annotated_body, body),
+        |arena: &'a Bump, ann_body_or_body| match ann_body_or_body {
+            Either::First((body_pattern, body_expr)) =>
+                Def::Body(arena.alloc(body_pattern), arena.alloc(body_expr)),
+            Either::Second(((ann_pattern, ann_type), None)) => annotation_or_alias(
+                arena,
+                &(ann_pattern as Located<Pattern>).value,
+                (ann_pattern as Located<Pattern>).region,
+                ann_type
+            ),
+            Either::Second((
+                (ann_pattern, ann_type),
+                Some((opt_comment, (body_pattern, body_expr))),
+            )) => Def::AnnotatedBody {
+                ann_pattern: ann_pattern,
+                ann_type: ann_type,
+                comment: opt_comment,
+                body_pattern: body_pattern,
+                body_expr: body_expr,
+            },
         }
     )
 }