feat: Add warnings for usage of restricted bit sizes (#4234)

# Description

## Problem\*

Breaking change warning for
[#4162](#4162)
## Summary\*



## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [x] **[Exceptional Case]** 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/parser/errors.rs

@@ -40,6 +40,8 @@ pub enum ParserErrorReason {
     NoFunctionAttributesAllowedOnStruct,
     #[error("Assert statements can only accept string literals")]
     AssertMessageNotString,
+    #[error("Integer bit size {0} won't be supported")]
+    DeprecatedBitSize(u32),
     #[error("{0}")]
     Lexer(LexerErrorKind),
 }
@@ -130,6 +132,8 @@ impl std::fmt::Display for ParserError {
     }
 }
 
+pub(crate) static ALLOWED_INTEGER_BIT_SIZES: &[u32] = &[1, 8, 32, 64];
+
 impl From<ParserError> for Diagnostic {
     fn from(error: ParserError) -> Diagnostic {
         match error.reason {
@@ -145,6 +149,11 @@ impl From<ParserError> for Diagnostic {
                         "The 'comptime' keyword has been deprecated. It can be removed without affecting your program".into(),
                         error.span,
                     ),
+                    ParserErrorReason::DeprecatedBitSize(bit_size) => Diagnostic::simple_warning(
+                        format!("Use of deprecated bit size {}", bit_size),
+                        format!("Bit sizes for integers will be restricted to {}", ALLOWED_INTEGER_BIT_SIZES.iter().map(|n| n.to_string()).collect::<Vec<_>>().join(", ")),
+                        error.span,
+                    ),
                     ParserErrorReason::ExperimentalFeature(_) => Diagnostic::simple_warning(
                         reason.to_string(),
                         "".into(),

compiler/noirc_frontend/src/parser/parser.rs

@@ -23,6 +23,7 @@
 //! prevent other parsers from being tried afterward since there is no longer an error. Thus, they should
 //! be limited to cases like the above `fn` example where it is clear we shouldn't back out of the
 //! current parser to try alternative parsers in a `choice` expression.
+use super::errors::ALLOWED_INTEGER_BIT_SIZES;
 use super::{
     foldl_with_span, labels::ParsingRuleLabel, parameter_name_recovery, parameter_recovery,
     parenthesized, then_commit, then_commit_ignore, top_level_statement_recovery, ExprParser,
@@ -35,7 +36,7 @@ use crate::ast::{
 };
 use crate::lexer::Lexer;
 use crate::parser::{force, ignore_then_commit, statement_recovery};
-use crate::token::{Attribute, Attributes, Keyword, SecondaryAttribute, Token, TokenKind};
+use crate::token::{Attribute, Attributes, IntType, Keyword, SecondaryAttribute, Token, TokenKind};
 use crate::{
     BinaryOp, BinaryOpKind, BlockExpression, ConstrainKind, ConstrainStatement, Distinctness,
     ForLoopStatement, ForRange, FunctionDefinition, FunctionReturnType, FunctionVisibility, Ident,
@@ -1092,6 +1093,18 @@ fn int_type() -> impl NoirParser<UnresolvedType> {
                 Err(ParserError::expected_label(ParsingRuleLabel::IntegerType, unexpected, span))
             }
         }))
+        .validate(|int_type, span, emit| {
+            let bit_size = match int_type.1 {
+                IntType::Signed(bit_size) | IntType::Unsigned(bit_size) => bit_size,
+            };
+            if !ALLOWED_INTEGER_BIT_SIZES.contains(&bit_size) {
+                emit(ParserError::with_reason(
+                    ParserErrorReason::DeprecatedBitSize(bit_size),
+                    span,
+                ));
+            }
+            int_type
+        })
         .map_with_span(|(_, token), span| UnresolvedTypeData::from_int_token(token).with_span(span))
 }
 

noir_stdlib/src/cmp.nr

@@ -8,12 +8,10 @@ impl Eq for Field { fn eq(self, other: Field) -> bool { self == other } }
 
 impl Eq for u1 { fn eq(self, other: u1) -> bool { self == other } }
 impl Eq for u8 { fn eq(self, other: u8) -> bool { self == other } }
-impl Eq for u16 { fn eq(self, other: u16) -> bool { self == other } }
 impl Eq for u32 { fn eq(self, other: u32) -> bool { self == other } }
 impl Eq for u64 { fn eq(self, other: u64) -> bool { self == other } }
 
 impl Eq for i8 { fn eq(self, other: i8) -> bool { self == other } }
-impl Eq for i16 { fn eq(self, other: i16) -> bool { self == other } }
 impl Eq for i32 { fn eq(self, other: i32) -> bool { self == other } }
 impl Eq for i64 { fn eq(self, other: i64) -> bool { self == other } }
 
@@ -111,18 +109,6 @@ impl Ord for u8 {
     }
 }
 
-impl Ord for u16 {
-    fn cmp(self, other: u16) -> Ordering {
-        if self < other {
-            Ordering::less()
-        } else if self > other {
-            Ordering::greater()
-        } else {
-            Ordering::equal()
-        }
-    }
-}
-
 impl Ord for u32 {
     fn cmp(self, other: u32) -> Ordering {
         if self < other {
@@ -159,18 +145,6 @@ impl Ord for i8 {
     }
 }
 
-impl Ord for i16 {
-    fn cmp(self, other: i16) -> Ordering {
-        if self < other {
-            Ordering::less()
-        } else if self > other {
-            Ordering::greater()
-        } else {
-            Ordering::equal()
-        }
-    }
-}
-
 impl Ord for i32 {
     fn cmp(self, other: i32) -> Ordering {
         if self < other {

noir_stdlib/src/convert.nr

@@ -24,37 +24,28 @@ impl<T, U> Into<T> for U where T: From<U> {
 
 // docs:start:from-impls
 // Unsigned integers
-impl From<u8> for u16 { fn from(value: u8) -> u16 { value as u16 } }
 
 impl From<u8> for u32 { fn from(value: u8) -> u32 { value as u32 } }
-impl From<u16> for u32 { fn from(value: u16) -> u32 { value as u32 } }
 
 impl From<u8> for u64 { fn from(value: u8) -> u64 { value as u64 } }
-impl From<u16> for u64 { fn from(value: u16) -> u64 { value as u64 } }
 impl From<u32> for u64 { fn from(value: u32) -> u64 { value as u64 } }
 
 impl From<u8> for Field { fn from(value: u8) -> Field { value as Field } }
-impl From<u16> for Field { fn from(value: u16) -> Field { value as Field } }
 impl From<u32> for Field { fn from(value: u32) -> Field { value as Field } }
 impl From<u64> for Field { fn from(value: u64) -> Field { value as Field } }
 
 // Signed integers
-impl From<i8> for i16 { fn from(value: i8) -> i16 { value as i16 } }
 
 impl From<i8> for i32 { fn from(value: i8) -> i32 { value as i32 } }
-impl From<i16> for i32 { fn from(value: i16) -> i32 { value as i32 } }
 
 impl From<i8> for i64 { fn from(value: i8) -> i64 { value as i64 } }
-impl From<i16> for i64 { fn from(value: i16) -> i64 { value as i64 } }
 impl From<i32> for i64 { fn from(value: i32) -> i64 { value as i64 } }
 
 // Booleans
 impl From<bool> for u8 { fn from(value: bool) -> u8 { value as u8 } }
-impl From<bool> for u16 { fn from(value: bool) -> u16 { value as u16 } }
 impl From<bool> for u32 { fn from(value: bool) -> u32 { value as u32 } }
 impl From<bool> for u64 { fn from(value: bool) -> u64 { value as u64 } }
 impl From<bool> for i8 { fn from(value: bool) -> i8 { value as i8 } }
-impl From<bool> for i16 { fn from(value: bool) -> i16 { value as i16 } }
 impl From<bool> for i32 { fn from(value: bool) -> i32 { value as i32 } }
 impl From<bool> for i64 { fn from(value: bool) -> i64 { value as i64 } }
 impl From<bool> for Field { fn from(value: bool) -> Field { value as Field } }

noir_stdlib/src/default.nr

@@ -7,12 +7,10 @@ trait Default {
 impl Default for Field { fn default() -> Field { 0 } }
 
 impl Default for u8 { fn default() -> u8 { 0 } }
-impl Default for u16 { fn default() -> u16 { 0 } }
 impl Default for u32 { fn default() -> u32 { 0 } }
 impl Default for u64 { fn default() -> u64 { 0 } }
 
 impl Default for i8 { fn default() -> i8 { 0 } }
-impl Default for i16 { fn default() -> i16 { 0 } }
 impl Default for i32 { fn default() -> i32 { 0 } }
 impl Default for i64 { fn default() -> i64 { 0 } }
 

noir_stdlib/src/ops.nr

@@ -7,12 +7,10 @@ trait Add {
 impl Add for Field { fn add(self, other: Field) -> Field { self + other } }
 
 impl Add for u8 { fn add(self, other: u8) -> u8 { self + other } }
-impl Add for u16 { fn add(self, other: u16) -> u16 { self + other } }
 impl Add for u32 { fn add(self, other: u32) -> u32 { self + other } }
 impl Add for u64 { fn add(self, other: u64) -> u64 { self + other } }
 
 impl Add for i8 { fn add(self, other: i8) -> i8 { self + other } }
-impl Add for i16 { fn add(self, other: i16) -> i16 { self + other } }
 impl Add for i32 { fn add(self, other: i32) -> i32 { self + other } }
 impl Add for i64 { fn add(self, other: i64) -> i64 { self + other } }
 
@@ -25,12 +23,10 @@ trait Sub {
 impl Sub for Field { fn sub(self, other: Field) -> Field { self - other } }
 
 impl Sub for u8 { fn sub(self, other: u8) -> u8 { self - other } }
-impl Sub for u16 { fn sub(self, other: u16) -> u16 { self - other } }
 impl Sub for u32 { fn sub(self, other: u32) -> u32 { self - other } }
 impl Sub for u64 { fn sub(self, other: u64) -> u64 { self - other } }
 
 impl Sub for i8 { fn sub(self, other: i8) -> i8 { self - other } }
-impl Sub for i16 { fn sub(self, other: i16) -> i16 { self - other } }
 impl Sub for i32 { fn sub(self, other: i32) -> i32 { self - other } }
 impl Sub for i64 { fn sub(self, other: i64) -> i64 { self - other } }
 
@@ -43,12 +39,10 @@ trait Mul {
 impl Mul for Field { fn mul(self, other: Field) -> Field { self * other } }
 
 impl Mul for u8 { fn mul(self, other: u8) -> u8 { self * other } }
-impl Mul for u16 { fn mul(self, other: u16) -> u16 { self * other } }
 impl Mul for u32 { fn mul(self, other: u32) -> u32 { self * other } }
 impl Mul for u64 { fn mul(self, other: u64) -> u64 { self * other } }
 
 impl Mul for i8 { fn mul(self, other: i8) -> i8 { self * other } }
-impl Mul for i16 { fn mul(self, other: i16) -> i16 { self * other } }
 impl Mul for i32 { fn mul(self, other: i32) -> i32 { self * other } }
 impl Mul for i64 { fn mul(self, other: i64) -> i64 { self * other } }
 
@@ -61,12 +55,10 @@ trait Div {
 impl Div for Field { fn div(self, other: Field) -> Field { self / other } }
 
 impl Div for u8 { fn div(self, other: u8) -> u8 { self / other } }
-impl Div for u16 { fn div(self, other: u16) -> u16 { self / other } }
 impl Div for u32 { fn div(self, other: u32) -> u32 { self / other } }
 impl Div for u64 { fn div(self, other: u64) -> u64 { self / other } }
 
 impl Div for i8 { fn div(self, other: i8) -> i8 { self / other } }
-impl Div for i16 { fn div(self, other: i16) -> i16 { self / other } }
 impl Div for i32 { fn div(self, other: i32) -> i32 { self / other } }
 impl Div for i64 { fn div(self, other: i64) -> i64 { self / other } }
 
@@ -77,12 +69,10 @@ trait Rem{
 // docs:end:rem-trait
 
 impl Rem for u8 { fn rem(self, other: u8) -> u8 { self % other } }
-impl Rem for u16 { fn rem(self, other: u16) -> u16 { self % other } }
 impl Rem for u32 { fn rem(self, other: u32) -> u32 { self % other } }
 impl Rem for u64 { fn rem(self, other: u64) -> u64 { self % other } }
 
 impl Rem for i8 { fn rem(self, other: i8) -> i8 { self % other } }
-impl Rem for i16 { fn rem(self, other: i16) -> i16 { self % other } }
 impl Rem for i32 { fn rem(self, other: i32) -> i32 { self % other } }
 impl Rem for i64 { fn rem(self, other: i64) -> i64 { self % other } }
 
@@ -95,12 +85,10 @@ trait BitOr {
 impl BitOr for bool { fn bitor(self, other: bool) -> bool { self | other } }
 
 impl BitOr for u8 { fn bitor(self, other: u8) -> u8 { self | other } }
-impl BitOr for u16 { fn bitor(self, other: u16) -> u16 { self | other } }
 impl BitOr for u32 { fn bitor(self, other: u32) -> u32 { self | other } }
 impl BitOr for u64 { fn bitor(self, other: u64) -> u64 { self | other } }
 
 impl BitOr for i8 { fn bitor(self, other: i8) -> i8 { self | other } }
-impl BitOr for i16 { fn bitor(self, other: i16) -> i16 { self | other } }
 impl BitOr for i32 { fn bitor(self, other: i32) -> i32 { self | other } }
 impl BitOr for i64 { fn bitor(self, other: i64) -> i64 { self | other } }
 
@@ -113,12 +101,10 @@ trait BitAnd {
 impl BitAnd for bool { fn bitand(self, other: bool) -> bool { self & other } }
 
 impl BitAnd for u8 { fn bitand(self, other: u8) -> u8 { self & other } }
-impl BitAnd for u16 { fn bitand(self, other: u16) -> u16 { self & other } }
 impl BitAnd for u32 { fn bitand(self, other: u32) -> u32 { self & other } }
 impl BitAnd for u64 { fn bitand(self, other: u64) -> u64 { self & other } }
 
 impl BitAnd for i8 { fn bitand(self, other: i8) -> i8 { self & other } }
-impl BitAnd for i16 { fn bitand(self, other: i16) -> i16 { self & other } }
 impl BitAnd for i32 { fn bitand(self, other: i32) -> i32 { self & other } }
 impl BitAnd for i64 { fn bitand(self, other: i64) -> i64 { self & other } }
 
@@ -131,12 +117,10 @@ trait BitXor {
 impl BitXor for bool { fn bitxor(self, other: bool) -> bool { self ^ other } }
 
 impl BitXor for u8 { fn bitxor(self, other: u8) -> u8 { self ^ other } }
-impl BitXor for u16 { fn bitxor(self, other: u16) -> u16 { self ^ other } }
 impl BitXor for u32 { fn bitxor(self, other: u32) -> u32 { self ^ other } }
 impl BitXor for u64 { fn bitxor(self, other: u64) -> u64 { self ^ other } }
 
 impl BitXor for i8 { fn bitxor(self, other: i8) -> i8 { self ^ other } }
-impl BitXor for i16 { fn bitxor(self, other: i16) -> i16 { self ^ other } }
 impl BitXor for i32 { fn bitxor(self, other: i32) -> i32 { self ^ other } }
 impl BitXor for i64 { fn bitxor(self, other: i64) -> i64 { self ^ other } }
 
@@ -147,13 +131,11 @@ trait Shl {
 // docs:end:shl-trait
 
 impl Shl for u8 { fn shl(self, other: u8) -> u8 { self << other } }
-impl Shl for u16 { fn shl(self, other: u16) -> u16 { self << other } }
 impl Shl for u32 { fn shl(self, other: u32) -> u32 { self << other } }
 impl Shl for u64 { fn shl(self, other: u64) -> u64 { self << other } }
 
 // Bit shifting is not currently supported for signed integer types
 // impl Shl for i8 { fn shl(self, other: i8) -> i8 { self << other } }
-// impl Shl for i16 { fn shl(self, other: i16) -> i16 { self << other } }
 // impl Shl for i32 { fn shl(self, other: i32) -> i32 { self << other } }
 // impl Shl for i64 { fn shl(self, other: i64) -> i64 { self << other } }
 
@@ -164,12 +146,10 @@ trait Shr {
 // docs:end:shr-trait
 
 impl Shr for u8 { fn shr(self, other: u8) -> u8 { self >> other } }
-impl Shr for u16 { fn shr(self, other: u16) -> u16 { self >> other } }
 impl Shr for u32 { fn shr(self, other: u32) -> u32 { self >> other } }
 impl Shr for u64 { fn shr(self, other: u64) -> u64 { self >> other } }
 
 // Bit shifting is not currently supported for signed integer types
 // impl Shr for i8 { fn shr(self, other: i8) -> i8 { self >> other } }
-// impl Shr for i16 { fn shr(self, other: i16) -> i16 { self >> other } }
 // impl Shr for i32 { fn shr(self, other: i32) -> i32 { self >> other } }
 // impl Shr for i64 { fn shr(self, other: i64) -> i64 { self >> other } }

test_programs/compile_success_empty/brillig_cast/src/main.nr

@@ -17,33 +17,25 @@ unconstrained fn bool_casts() {
 
 unconstrained fn field_casts() {
     assert(5 as u8 as Field == 5);
-    assert(16 as u4 as Field == 0);
+    assert(256 as u8 as Field == 0);
 }
 
 unconstrained fn uint_casts() {
-    let x: u32 = 100;
-    assert(x as u2 == 0);
-    assert(x as u4 == 4);
-    assert(x as u6 == 36);
-    assert(x as u8 == 100);
-    assert(x as u64 == 100);
-    assert(x as u126 == 100);
+    let x: u32 = 300;
+    assert(x as u8 == 44);
+    assert(x as u32 == 300);
+    assert(x as u64 == 300);
 }
 
 unconstrained fn int_casts() {
-    let x: i32 = 100;
-    assert(x as i2 == 0);
-    assert(x as i4 == 4);
-    assert(x as i6 == -28 as i6);
-    assert(x as i8 == 100);
-    assert(x as i8 == 100);
-    assert(x as i8 == 100);
+    let x: i32 = 456;
+    assert(x as i8 == -56 as i8);
+    assert(x as i64 == 456);
 }
 
 unconstrained fn mixed_casts() {
     assert(100 as u32 as i32 as u32 == 100);
-    assert(13 as u4 as i2 as u32 == 1);
-    assert(15 as u4 as i2 as u32 == 3);
+    assert(257 as u8 as u32 == 1);
     assert(1 as u8 as bool == true);
     assert(true as i8 == 1);
 }

test_programs/compile_success_empty/brillig_modulo/src/main.nr

@@ -7,9 +7,9 @@ fn main() {
     assert(signed_modulo(5, 3) == 2);
     assert(signed_modulo(2, 3) == 2);
 
-    let minus_two: i4 = -2; // 14
-    let minus_three: i4 = -3; // 13
-    let minus_five: i4 = -5; // 11
+    let minus_two: i8 = -2; // 254
+    let minus_three: i8 = -3; // 253
+    let minus_five: i8 = -5; // 251
     // (5 / -3) * -3 + 2 = -1 * -3 + 2 = 3 + 2 = 5
     assert(signed_modulo(5, minus_three) == 2);
     // (-5 / 3) * 3 - 2 = -1 * 3 - 2 = -3 - 2 = -5
@@ -22,6 +22,6 @@ unconstrained fn modulo(x: u32, y: u32) -> u32 {
     x % y
 }
 
-unconstrained fn signed_modulo(x: i4, y: i4) -> i4 {
+unconstrained fn signed_modulo(x: i8, y: i8) -> i8 {
     x % y
 }

test_programs/execution_success/5_over/src/main.nr

@@ -5,6 +5,6 @@ fn main(mut x: u32, y: u32) {
     x = std::wrapping_mul(x,x);
     assert(y == x);
 
-    let c: u3 = 2;
-    assert(c > x as u3);
+    let c: u1 = 0;
+    assert(x as u1 > c);
 }

test_programs/execution_success/bit_shifts_comptime/src/main.nr

@@ -14,7 +14,7 @@ fn main(x: u64) {
     //regression for 3481
     assert(x << 63 == 0);
 
-    assert_eq((1 as u56) << (32 as u56), 0x0100000000);
+    assert_eq((1 as u64) << (32 as u64), 0x0100000000);
 }
 
 fn regression_2250() {

test_programs/execution_success/conditional_regression_underflow/src/main.nr

@@ -1,12 +1,12 @@
 // Regression test for https://github.com/noir-lang/noir/issues/3493
-fn main(x: u4) {
+fn main(x: u8) {
     if x == 10 {
-        x + 15;
+        x + 255;
     }
     if x == 9 {
-        x << 3;
+        x << 7;
     }
-    if x == 8 {
+    if x == 128 {
         x * 3;
     }
     if x == 7 {