From f3ee0bef40ff1b20797fd20628d792fc6e29a911 Mon Sep 17 00:00:00 2001
From: satotake <doublequotation@gmail.com>
Date: Sun, 7 Nov 2021 12:27:43 +0000
Subject: [PATCH] Add `keep_shadowed_builtins` feature to roc_parse

---
 compiler/parse/Cargo.toml   |  5 +++++
 compiler/parse/src/ident.rs | 33 +++++++++++++++++++++------------
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/compiler/parse/Cargo.toml b/compiler/parse/Cargo.toml
index 471d6c33c5..47933cee7d 100644
--- a/compiler/parse/Cargo.toml
+++ b/compiler/parse/Cargo.toml
@@ -5,6 +5,11 @@ authors = ["The Roc Contributors"]
 license = "UPL-1.0"
 edition = "2018"
 
+[features]
+# If enabled, parser accepts `Dict.#hashTestOnly` etc.
+# For development puporpse.
+keep_shadowed_builtins = []
+
 [dependencies]
 roc_collections = { path = "../collections" }
 roc_region = { path = "../region" }
diff --git a/compiler/parse/src/ident.rs b/compiler/parse/src/ident.rs
index 2adf44fa05..36b07939c3 100644
--- a/compiler/parse/src/ident.rs
+++ b/compiler/parse/src/ident.rs
@@ -220,6 +220,10 @@ pub enum BadIdent {
     BadPrivateTag(Row, Col),
 }
 
+fn chomp_lowercase_part_keep_shadowed_builtins(buffer: &[u8]) -> Result<&str, Progress> {
+    chomp_part(|c: char| c.is_lowercase() || c == '#', buffer)
+}
+
 fn chomp_lowercase_part(buffer: &[u8]) -> Result<&str, Progress> {
     chomp_part(|c: char| c.is_lowercase(), buffer)
 }
@@ -499,19 +503,24 @@ fn chomp_access_chain<'a>(buffer: &'a [u8], parts: &mut Vec<'a, &'a str>) -> Res
 
     while let Some(b'.') = buffer.get(chomped) {
         match &buffer.get(chomped + 1..) {
-            Some(slice) => match chomp_lowercase_part(slice) {
-                Ok(name) => {
-                    let value = unsafe {
-                        std::str::from_utf8_unchecked(
-                            &buffer[chomped + 1..chomped + 1 + name.len()],
-                        )
-                    };
-                    parts.push(value);
-
-                    chomped += name.len() + 1;
+            Some(slice) => {
+                let res = match cfg!(feature = "keep_shadowed_builtins") {
+                    true => chomp_lowercase_part_keep_shadowed_builtins(slice),
+                    false => chomp_lowercase_part(slice),
+                };
+                match res {
+                    Ok(name) => {
+                        let value = unsafe {
+                            std::str::from_utf8_unchecked(
+                                &buffer[chomped + 1..chomped + 1 + name.len()],
+                            )
+                        };
+                        parts.push(value);
+                        chomped += name.len() + 1;
+                    }
+                    Err(_) => return Err(chomped as u16 + 1),
                 }
-                Err(_) => return Err(chomped as u16 + 1),
-            },
+            }
             None => return Err(chomped as u16 + 1),
         }
     }