feat: better error message when keyword is found instead of type in p… (

#7501)

Co-authored-by: Tom French <[email protected]>

compiler/noirc_frontend/src/parser/parser/function.rs

@@ -196,7 +196,10 @@ impl<'a> Parser<'a> {
                 UnresolvedType { typ: UnresolvedTypeData::Error, location: Location::dummy() };
             (visibility, typ)
         } else {
-            (self.parse_visibility(), self.parse_type_or_error())
+            (
+                self.parse_visibility(),
+                self.parse_type_or_error_with_recovery(&[Token::Comma, Token::RightParen]),
+            )
         };
 
         Param { visibility, pattern, typ, location: self.location_since(start_location) }
@@ -306,7 +309,10 @@ fn empty_body() -> BlockExpression {
 #[cfg(test)]
 mod tests {
     use crate::{
-        ast::{ItemVisibility, NoirFunction, UnresolvedTypeData, Visibility},
+        ast::{
+            IntegerBitSize, ItemVisibility, NoirFunction, Signedness, UnresolvedTypeData,
+            Visibility,
+        },
         parse_program_with_dummy_file,
         parser::{
             parser::tests::{
@@ -520,4 +526,34 @@ mod tests {
         let reason = get_single_error_reason(&errors, span);
         assert!(matches!(reason, ParserErrorReason::MissingParametersForFunctionDefinition));
     }
+
+    #[test]
+    fn parse_function_with_keyword_before_type() {
+        let src = "
+        fn foo(x: mut i32, y: i64) {}
+                  ^^^
+        ";
+        let (src, span) = get_source_with_error_span(src);
+        let (mut module, errors) = parse_program_with_dummy_file(&src);
+        let error = get_single_error(&errors, span);
+        assert_eq!(error.to_string(), "Expected a type but found 'mut'");
+
+        assert_eq!(module.items.len(), 1);
+        let item = module.items.remove(0);
+        let ItemKind::Function(noir_function) = item.kind else {
+            panic!("Expected function");
+        };
+
+        let params = noir_function.parameters();
+        assert_eq!(params.len(), 2);
+
+        assert_eq!(
+            params[0].typ.typ,
+            UnresolvedTypeData::Integer(Signedness::Signed, IntegerBitSize::ThirtyTwo)
+        );
+        assert_eq!(
+            params[1].typ.typ,
+            UnresolvedTypeData::Integer(Signedness::Signed, IntegerBitSize::SixtyFour)
+        );
+    }
 }

compiler/noirc_frontend/src/parser/parser/types.rs

@@ -19,6 +19,26 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Tries to parse a type. If the current token doesn't denote a type and it's not
+    /// one of `stop_tokens`, try to parse a type starting from the next token (and so on).
+    pub(crate) fn parse_type_or_error_with_recovery(
+        &mut self,
+        stop_tokens: &[Token],
+    ) -> UnresolvedType {
+        loop {
+            let typ = self.parse_type_or_error();
+            if typ.typ != UnresolvedTypeData::Error {
+                return typ;
+            }
+
+            if self.at_eof() || stop_tokens.contains(self.token.token()) {
+                return typ;
+            }
+
+            self.bump();
+        }
+    }
+
     pub(crate) fn parse_type(&mut self) -> Option<UnresolvedType> {
         let start_location = self.current_token_location;
         let typ = self.parse_unresolved_type_data()?;