warn on unneccessary brackets (#4769)

Signed-off-by: Nick Cameron <nrc@ncameron.org>

.codespellrc

@@ -1,3 +1,3 @@
 [codespell]
-ignore-words-list: crate,everytime,inout,co-ordinate,ot,nwo,absolutey,atleast,ue,afterall
+ignore-words-list: crate,everytime,inout,co-ordinate,ot,nwo,absolutey,atleast,ue,afterall,ket
 skip: **/target,node_modules,build,**/Cargo.lock,./docs/kcl/*.md,.yarn.lock,**/yarn.lock,./openapi/*.json,./src/lib/machine-api.d.ts

src/wasm-lib/kcl/src/parsing/parser.rs

@@ -4,7 +4,7 @@
 use std::{cell::RefCell, collections::HashMap, str::FromStr};
 
 use winnow::{
-    combinator::{alt, delimited, opt, peek, preceded, repeat, separated, separated_pair, terminated},
+    combinator::{alt, opt, peek, preceded, repeat, separated, separated_pair, terminated},
     dispatch,
     error::{ErrMode, StrContext, StrContextValue},
     prelude::*,
@@ -1662,12 +1662,24 @@ fn label(i: &mut TokenSlice) -> PResult<Node<Identifier>> {
 }
 
 fn unnecessarily_bracketed(i: &mut TokenSlice) -> PResult<Expr> {
-    delimited(
+    let (bra, result, ket) = (
         terminated(open_paren, opt(whitespace)),
         expression,
         preceded(opt(whitespace), close_paren),
     )
-    .parse_next(i)
+        .parse_next(i)?;
+
+    let expr_range: SourceRange = (&result).into();
+
+    ParseContext::warn(CompilationError::with_suggestion(
+        SourceRange::new(bra.start, ket.end, result.module_id()),
+        None,
+        "Unnecessary parentheses around sub-expression",
+        Some(("Remove parentheses", i.text(expr_range))),
+        Tag::Unnecessary,
+    ));
+
+    Ok(result)
 }
 
 fn expr_allowed_in_pipe_expr(i: &mut TokenSlice) -> PResult<Expr> {
@@ -4243,6 +4255,15 @@ var baz = 2
 "#
         );
     }
+
+    #[test]
+    fn warn_unneccessary_parens() {
+        let some_program_string = r#"foo((a + b))"#;
+        let (_, errs) = assert_no_err(some_program_string);
+        assert_eq!(errs.len(), 1);
+        let replaced = errs[0].apply_suggestion(some_program_string).unwrap();
+        assert_eq!(replaced, r#"foo(a + b)"#);
+    }
 }
 
 #[cfg(test)]

src/wasm-lib/kcl/src/parsing/token/mod.rs

@@ -27,11 +27,18 @@ pub(crate) use tokeniser::RESERVED_WORDS;
 #[derive(Clone, Debug, PartialEq)]
 pub(crate) struct TokenStream {
     tokens: Vec<Token>,
+    // TODO this could easily be borrowed except that the LSP caches token streams
+    source: String,
+    module_id: ModuleId,
 }
 
 impl TokenStream {
-    fn new(tokens: Vec<Token>) -> Self {
-        Self { tokens }
+    fn new(tokens: Vec<Token>, source: String, module_id: ModuleId) -> Self {
+        Self {
+            tokens,
+            source,
+            module_id,
+        }
     }
 
     pub(super) fn remove_unknown(&mut self) -> Vec<Token> {
@@ -54,6 +61,11 @@ impl TokenStream {
     pub fn as_slice(&self) -> TokenSlice {
         TokenSlice::from(self)
     }
+
+    pub fn text(&self, range: SourceRange) -> &str {
+        debug_assert_eq!(range.module_id(), self.module_id);
+        &self.source[range.start()..range.end()]
+    }
 }
 
 impl<'a> From<&'a TokenStream> for TokenSlice<'a> {
@@ -96,6 +108,10 @@ impl<'a> TokenSlice<'a> {
         &self.stream.tokens[i + self.start]
     }
 
+    pub fn text(&self, range: SourceRange) -> &str {
+        self.stream.text(range)
+    }
+
     pub fn iter(&self) -> impl Iterator<Item = &Token> {
         (**self).iter()
     }

src/wasm-lib/kcl/src/parsing/token/tokeniser.rs

@@ -69,7 +69,11 @@ pub(super) fn lex(i: &str, module_id: ModuleId) -> Result<TokenStream, ParseErro
         input: Located::new(i),
         state,
     };
-    Ok(TokenStream::new(repeat(0.., token).parse(input)?))
+    Ok(TokenStream::new(
+        repeat(0.., token).parse(input)?,
+        i.to_owned(),
+        module_id,
+    ))
 }
 
 pub(super) type Input<'a> = Stateful<Located<&'a str>, State>;