Check for overflow in computed flags

Author: meithecatte

enumflags_derive/src/lib.rs

@@ -12,12 +12,14 @@ use syn::{
     Ident, Item, ItemEnum, Token,
 };
 
+#[derive(Debug)]
 struct Flag {
     name: Ident,
     span: Span,
     value: FlagValue,
 }
 
+#[derive(Debug)]
 enum FlagValue {
     Literal(u128),
     Deferred,
@@ -88,6 +90,9 @@ fn fold_expr(expr: &syn::Expr) -> Option<u128> {
                 _ => None,
             }
         }
+        Expr::Paren(syn::ExprParen { expr, .. }) | Expr::Group(syn::ExprGroup { expr, .. }) => {
+            fold_expr(&expr)
+        }
         _ => None,
     }
 }
@@ -187,7 +192,7 @@ fn type_bits(ty: &Ident) -> Result<u8, syn::Error> {
 }
 
 /// Returns deferred checks
-fn check_flag(type_name: &Ident, flag: &Flag) -> Result<Option<TokenStream>, syn::Error> {
+fn check_flag(type_name: &Ident, flag: &Flag, bits: u8) -> Result<Option<TokenStream>, syn::Error> {
     use FlagValue::*;
     match flag.value {
         Literal(n) => {
@@ -196,6 +201,11 @@ fn check_flag(type_name: &Ident, flag: &Flag) -> Result<Option<TokenStream>, syn
                     flag.span,
                     "Flags must have exactly one set bit",
                 ))
+            } else if bits < 128 && n >= 1 << bits {
+                Err(syn::Error::new(
+                    flag.span,
+                    format!("Flag value out of range for u{}", bits),
+                ))
             } else {
                 Ok(None)
             }
@@ -235,17 +245,17 @@ fn gen_enumflags(ast: &ItemEnum, default: Vec<Ident>) -> Result<TokenStream, syn
     let variant_names = ast.variants.iter().map(|v| &v.ident).collect::<Vec<_>>();
     let repeated_name = vec![&ident; ast.variants.len()];
 
-    let variants = collect_flags(ast.variants.iter())?;
-    let deferred = variants
-        .iter()
-        .flat_map(|variant| check_flag(ident, variant).transpose())
-        .collect::<Result<Vec<_>, _>>()?;
-
     let ty = extract_repr(&ast.attrs)?
         .ok_or_else(|| syn::Error::new_spanned(&ident,
                         "repr attribute missing. Add #[repr(u64)] or a similar attribute to specify the size of the bitfield."))?;
     let bits = type_bits(&ty)?;
 
+    let variants = collect_flags(ast.variants.iter())?;
+    let deferred = variants
+        .iter()
+        .flat_map(|variant| check_flag(ident, variant, bits).transpose())
+        .collect::<Result<Vec<_>, _>>()?;
+
     if (bits as usize) < variants.len() {
         return Err(syn::Error::new_spanned(
             &ty,

test_suite/ui/missing_disciminant.rs

@@ -1,4 +1,5 @@
 #[enumflags2::bitflags]
+#[repr(u8)]
 #[derive(Copy, Clone)]
 enum Foo {
     OhNoTheresNoDiscriminant,

test_suite/ui/missing_disciminant.stderr

@@ -1,5 +1,5 @@
 error: Please add an explicit discriminant
- --> $DIR/missing_disciminant.rs:4:5
+ --> $DIR/missing_disciminant.rs:5:5
   |
-4 |     OhNoTheresNoDiscriminant,
+5 |     OhNoTheresNoDiscriminant,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^

test_suite/ui/multiple_bits.rs

@@ -1,4 +1,5 @@
 #[enumflags2::bitflags]
+#[repr(u8)]
 #[derive(Copy, Clone)]
 enum Foo {
     SingleBit = 1,

test_suite/ui/multiple_bits.stderr

@@ -1,5 +1,5 @@
 error: Flags must have exactly one set bit
- --> $DIR/multiple_bits.rs:5:5
+ --> $DIR/multiple_bits.rs:6:5
   |
-5 |     MultipleBits = 6,
+6 |     MultipleBits = 6,
   |     ^^^^^^^^^^^^^^^^

test_suite/ui/shift_out_of_range.rs

@@ -12,4 +12,11 @@ enum Bar {
     BigNumber = 1 << 20,
 }
 
+#[enumflags2::bitflags]
+#[repr(u16)]
+#[derive(Copy, Clone)]
+enum Baz {
+    BigNumber = (1 << 10) << 10,
+}
+
 fn main() {}

test_suite/ui/shift_out_of_range.stderr

@@ -1,3 +1,21 @@
+error: Flag value out of range for u64
+ --> $DIR/shift_out_of_range.rs:5:5
+  |
+5 |     BigNumber = 1 << 69,
+  |     ^^^^^^^^^^^^^^^^^^^
+
+error: Flag value out of range for u16
+  --> $DIR/shift_out_of_range.rs:12:5
+   |
+12 |     BigNumber = 1 << 20,
+   |     ^^^^^^^^^^^^^^^^^^^
+
+error: Flag value out of range for u16
+  --> $DIR/shift_out_of_range.rs:19:5
+   |
+19 |     BigNumber = (1 << 10) << 10,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0080]: evaluation of constant value failed
  --> $DIR/shift_out_of_range.rs:5:17
   |

test_suite/ui/with_fields.rs

@@ -1,4 +1,5 @@
 #[enumflags2::bitflags]
+#[repr(u8)]
 #[derive(Copy, Clone)]
 enum Foo {
     Bar(u32),

test_suite/ui/with_fields.stderr

@@ -1,5 +1,5 @@
 error: Bitflag variants cannot contain additional data
- --> $DIR/with_fields.rs:4:8
+ --> $DIR/with_fields.rs:5:8
   |
-4 |     Bar(u32),
+5 |     Bar(u32),
   |        ^^^^^

test_suite/ui/zero_disciminant.rs

@@ -1,4 +1,5 @@
 #[enumflags2::bitflags]
+#[repr(u8)]
 #[derive(Copy, Clone)]
 enum Foo {
     Zero = 0,