feat!: error on too large integer value (noir-lang#5371)

# Description

## Problem

Resolves noir-lang#4631

## Summary

Changes the lexer to error if an integer literal is greater than or
equal to the field element modulus.

## Additional Context

None.

## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

compiler/noirc_frontend/src/lexer/errors.rs

@@ -15,6 +15,8 @@ pub enum LexerErrorKind {
     NotADoubleChar { span: Span, found: Token },
     #[error("Invalid integer literal, {:?} is not a integer", found)]
     InvalidIntegerLiteral { span: Span, found: String },
+    #[error("Integer literal is too large")]
+    IntegerLiteralTooLarge { span: Span, limit: String },
     #[error("{:?} is not a valid attribute", found)]
     MalformedFuncAttribute { span: Span, found: String },
     #[error("Logical and used instead of bitwise and")]
@@ -46,6 +48,7 @@ impl LexerErrorKind {
             LexerErrorKind::UnexpectedCharacter { span, .. } => *span,
             LexerErrorKind::NotADoubleChar { span, .. } => *span,
             LexerErrorKind::InvalidIntegerLiteral { span, .. } => *span,
+            LexerErrorKind::IntegerLiteralTooLarge { span, .. } => *span,
             LexerErrorKind::MalformedFuncAttribute { span, .. } => *span,
             LexerErrorKind::LogicalAnd { span } => *span,
             LexerErrorKind::UnterminatedBlockComment { span } => *span,
@@ -83,6 +86,11 @@ impl LexerErrorKind {
                 format!(" {found} is not an integer"),
                 *span,
             ),
+            LexerErrorKind::IntegerLiteralTooLarge { span, limit } => (
+                "Integer literal is too large".to_string(),
+                format!("value exceeds limit of {limit}"),
+                *span,
+            ),
             LexerErrorKind::MalformedFuncAttribute { span, found } => (
                 "Malformed function attribute".to_string(),
                 format!(" {found} is not a valid attribute"),

compiler/noirc_frontend/src/lexer/lexer.rs

@@ -6,9 +6,11 @@ use super::{
         token_to_borrowed_token, BorrowedToken, IntType, Keyword, SpannedToken, Token, Tokens,
     },
 };
-use acvm::FieldElement;
+use acvm::{AcirField, FieldElement};
 use noirc_errors::{Position, Span};
-use std::str::CharIndices;
+use num_bigint::BigInt;
+use num_traits::{Num, One};
+use std::str::{CharIndices, FromStr};
 
 /// The job of the lexer is to transform an iterator of characters (`char_iter`)
 /// into an iterator of `SpannedToken`. Each `Token` corresponds roughly to 1 word or operator.
@@ -19,6 +21,7 @@ pub struct Lexer<'a> {
     done: bool,
     skip_comments: bool,
     skip_whitespaces: bool,
+    max_integer: BigInt,
 }
 
 pub type SpannedTokenResult = Result<SpannedToken, LexerErrorKind>;
@@ -61,6 +64,8 @@ impl<'a> Lexer<'a> {
             done: false,
             skip_comments: true,
             skip_whitespaces: true,
+            max_integer: BigInt::from_biguint(num_bigint::Sign::Plus, FieldElement::modulus())
+                - BigInt::one(),
         }
     }
 
@@ -376,14 +381,28 @@ impl<'a> Lexer<'a> {
         // Underscores needs to be stripped out before the literal can be converted to a `FieldElement.
         let integer_str = integer_str.replace('_', "");
 
-        let integer = match FieldElement::try_from_str(&integer_str) {
-            None => {
+        let bigint_result = match integer_str.strip_prefix("0x") {
+            Some(integer_str) => BigInt::from_str_radix(integer_str, 16),
+            None => BigInt::from_str(&integer_str),
+        };
+
+        let integer = match bigint_result {
+            Ok(bigint) => {
+                if bigint > self.max_integer {
+                    return Err(LexerErrorKind::IntegerLiteralTooLarge {
+                        span: Span::inclusive(start, end),
+                        limit: self.max_integer.to_string(),
+                    });
+                }
+                let big_uint = bigint.magnitude();
+                FieldElement::from_be_bytes_reduce(&big_uint.to_bytes_be())
+            }
+            Err(_) => {
                 return Err(LexerErrorKind::InvalidIntegerLiteral {
                     span: Span::inclusive(start, end),
                     found: integer_str,
                 })
             }
-            Some(integer) => integer,
         };
 
         let integer_token = Token::Int(integer);
@@ -899,6 +918,19 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_int_too_large() {
+        let modulus = FieldElement::modulus();
+        let input = modulus.to_string();
+
+        let mut lexer = Lexer::new(&input);
+        let token = lexer.next_token();
+        assert!(
+            matches!(token, Err(LexerErrorKind::IntegerLiteralTooLarge { .. })),
+            "expected {input} to throw error"
+        );
+    }
+
     #[test]
     fn test_arithmetic_sugar() {
         let input = "+= -= *= /= %=";

test_programs/compile_failure/integer_too_large/Nargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "integer_too_large"
+type = "bin"
+authors = [""]
+[dependencies]

test_programs/compile_failure/integer_too_large/src/main.nr

@@ -0,0 +1,4 @@
+fn main(x: Field) {
+    let too_large: Field = 233149999999999999999999999999999999999999999999999999999999923314999999999999999999999999999999999999999999999999999999999923314999999999999999999999999999999999999999999999999999999999;
+    assert(x == too_large);
+}

test_programs/compile_success_empty/ec_baby_jubjub/src/main.nr

@@ -9,10 +9,11 @@ use std::ec::swcurve::curvegroup::Point as SWG;
 
 use std::ec::montcurve::affine::Point as MGaffine;
 use std::ec::montcurve::curvegroup::Point as MG;
+use std::compat;
 
 fn main() {
     // This test only makes sense if Field is the right prime field.
-    if 21888242871839275222246405745257275088548364400416034343698204186575808495617 == 0 {
+    if compat::is_bn254() {
         // Define Baby Jubjub (ERC-2494) parameters in affine representation
         let bjj_affine = AffineCurve::new(
             168700,