crash upon integer overflow

compiler/builtins/src/std.rs

@@ -187,6 +187,26 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         ),
     );
 
+    // addChecked or (+) : Num a, Num a -> Result (Num a) [ IntOverflow ]*
+    let int_overflow = SolvedType::TagUnion(
+        vec![(TagName::Global("IntOverflow".into()), vec![])],
+        Box::new(SolvedType::Wildcard),
+    );
+
+    add_type(
+        Symbol::NUM_ADD_CHECKED,
+        SolvedType::Func(
+            vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
+            Box::new(result_type(num_type(flex(TVAR1)), int_overflow)),
+        ),
+    );
+
+    // addWrap or (+) : Int, Int -> Int
+    add_type(
+        Symbol::NUM_ADD_WRAP,
+        SolvedType::Func(vec![int_type(), int_type()], Box::new(int_type())),
+    );
+
     // sub or (-) : Num a, Num a -> Num a
     add_type(
         Symbol::NUM_SUB,

compiler/builtins/src/unique.rs

@@ -274,6 +274,26 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         unique_function(vec![num_type(u, num), num_type(v, num)], num_type(w, num))
     });
 
+    // addChecked or (+) : Num a, Num a -> Result (Num a) [ IntOverflow ]*
+    let int_overflow = SolvedType::TagUnion(
+        vec![(TagName::Global("IntOverflow".into()), vec![])],
+        Box::new(SolvedType::Wildcard),
+    );
+
+    add_type(Symbol::NUM_ADD_CHECKED, {
+        let_tvars! { u, v, w, num, result, star };
+        unique_function(
+            vec![num_type(u, num), num_type(v, num)],
+            result_type(result, num_type(w, num), lift(star, int_overflow)),
+        )
+    });
+
+    // addWrap or (+) : Int, Int -> Int
+    add_type(Symbol::NUM_ADD_WRAP, {
+        let_tvars! { u, v, w };
+        unique_function(vec![int_type(u), int_type(v)], int_type(w))
+    });
+
     // sub or (-) : Num a, Num a -> Num a
     add_type(Symbol::NUM_SUB, {
         let_tvars! { u, v, w, num };

compiler/gen/src/llvm/build.rs

@@ -270,6 +270,12 @@ fn add_intrinsics<'ctx>(ctx: &'ctx Context, module: &Module<'ctx>) {
         LLVM_FLOOR_F64,
         f64_type.fn_type(&[f64_type.into()], false),
     );
+
+    add_intrinsic(module, LLVM_SADD_WITH_OVERFLOW_I64, {
+        let fields = [i64_type.into(), i1_type.into()];
+        ctx.struct_type(&fields, false)
+            .fn_type(&[i64_type.into(), i64_type.into()], false)
+    });
 }
 
 static LLVM_MEMSET_I64: &str = "llvm.memset.p0i8.i64";
@@ -282,6 +288,7 @@ static LLVM_COS_F64: &str = "llvm.cos.f64";
 static LLVM_POW_F64: &str = "llvm.pow.f64";
 static LLVM_CEILING_F64: &str = "llvm.ceil.f64";
 static LLVM_FLOOR_F64: &str = "llvm.floor.f64";
+static LLVM_SADD_WITH_OVERFLOW_I64: &str = "llvm.sadd.with.overflow.i64";
 
 fn add_intrinsic<'ctx>(
     module: &Module<'ctx>,
@@ -2219,7 +2226,7 @@ fn run_low_level<'a, 'ctx, 'env>(
         }
 
         NumAdd | NumSub | NumMul | NumLt | NumLte | NumGt | NumGte | NumRemUnchecked
-        | NumDivUnchecked | NumPow | NumPowInt => {
+        | NumAddWrap | NumAddChecked | NumDivUnchecked | NumPow | NumPowInt => {
             debug_assert_eq!(args.len(), 2);
 
             let (lhs_arg, lhs_layout) = load_symbol_and_layout(env, scope, &args[0]);
@@ -2234,6 +2241,7 @@ fn run_low_level<'a, 'ctx, 'env>(
                     match lhs_builtin {
                         Int128 | Int64 | Int32 | Int16 | Int8 => build_int_binop(
                             env,
+                            parent,
                             lhs_arg.into_int_value(),
                             lhs_layout,
                             rhs_arg.into_int_value(),
@@ -2413,6 +2421,7 @@ where
 
 fn build_int_binop<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
+    parent: FunctionValue<'ctx>,
     lhs: IntValue<'ctx>,
     _lhs_layout: &Layout<'a>,
     rhs: IntValue<'ctx>,
@@ -2425,7 +2434,40 @@ fn build_int_binop<'a, 'ctx, 'env>(
     let bd = env.builder;
 
     match op {
-        NumAdd => bd.build_int_add(lhs, rhs, "add_int").into(),
+        NumAdd => {
+            // TODO
+            let builder = env.builder;
+            let context = env.context;
+
+            let result = env
+                .call_intrinsic(LLVM_SADD_WITH_OVERFLOW_I64, &[lhs.into(), rhs.into()])
+                .into_struct_value();
+
+            let add_result = bd.build_extract_value(result, 0, "add_result").unwrap();
+            let has_overflowed = bd.build_extract_value(result, 1, "has_overflowed").unwrap();
+
+            let condition = builder.build_int_compare(
+                IntPredicate::EQ,
+                has_overflowed.into_int_value(),
+                context.bool_type().const_zero(),
+                "has_not_overflowed",
+            );
+
+            let then_block = context.append_basic_block(parent, "then_block");
+            let throw_block = context.append_basic_block(parent, "throw_block");
+
+            builder.build_conditional_branch(condition, then_block, throw_block);
+
+            builder.position_at_end(throw_block);
+
+            throw_exception(env, "integer addition overflowed!");
+
+            builder.position_at_end(then_block);
+
+            add_result
+        }
+        NumAddWrap => bd.build_int_add(lhs, rhs, "add_int_wrap").into(),
+        NumAddChecked => bd.build_int_add(lhs, rhs, "add_int_checked").into(),
         NumSub => bd.build_int_sub(lhs, rhs, "sub_int").into(),
         NumMul => bd.build_int_mul(lhs, rhs, "mul_int").into(),
         NumGt => bd.build_int_compare(SGT, lhs, rhs, "int_gt").into(),
@@ -2475,6 +2517,8 @@ fn build_float_binop<'a, 'ctx, 'env>(
 
     match op {
         NumAdd => bd.build_float_add(lhs, rhs, "add_float").into(),
+        NumAddWrap => unreachable!("wrapping addition is not defined on floats"),
+        NumAddChecked => bd.build_float_add(lhs, rhs, "add_float_checked").into(),
         NumSub => bd.build_float_sub(lhs, rhs, "sub_float").into(),
         NumMul => bd.build_float_mul(lhs, rhs, "mul_float").into(),
         NumGt => bd.build_float_compare(OGT, lhs, rhs, "float_gt").into(),

compiler/gen/tests/gen_num.rs

@@ -685,4 +685,18 @@ mod gen_num {
     fn pow_int() {
         assert_evals_to!("Num.powInt 2 3", 8, i64);
     }
+
+    #[test]
+    #[should_panic(expected = r#"Roc failed with message: "integer addition overflowed!"#)]
+    fn int_overflow() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                9_223_372_036_854_775_807 + 1
+                "#
+            ),
+            0,
+            i64
+        );
+    }
 }

compiler/module/src/low_level.rs

@@ -20,6 +20,8 @@ pub enum LowLevel {
     ListKeepIf,
     ListWalkRight,
     NumAdd,
+    NumAddWrap,
+    NumAddChecked,
     NumSub,
     NumMul,
     NumGt,

compiler/module/src/symbol.rs

@@ -644,6 +644,8 @@ define_builtins! {
         39 NUM_CEILING: "ceiling"
         40 NUM_POW_INT: "powInt"
         41 NUM_FLOOR: "floor"
+        42 NUM_ADD_WRAP: "addWrap"
+        43 NUM_ADD_CHECKED: "addChecked"
     }
     2 BOOL: "Bool" => {
         0 BOOL_BOOL: "Bool" imported // the Bool.Bool type alias

compiler/mono/src/borrow.rs

@@ -521,10 +521,9 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         ListKeepIf => arena.alloc_slice_copy(&[owned, irrelevant]),
         ListWalkRight => arena.alloc_slice_copy(&[borrowed, irrelevant, owned]),
 
-        Eq | NotEq | And | Or | NumAdd | NumSub | NumMul | NumGt | NumGte | NumLt | NumLte
-        | NumCompare | NumDivUnchecked | NumRemUnchecked | NumPow | NumPowInt => {
-            arena.alloc_slice_copy(&[irrelevant, irrelevant])
-        }
+        Eq | NotEq | And | Or | NumAdd | NumAddWrap | NumAddChecked | NumSub | NumMul | NumGt
+        | NumGte | NumLt | NumLte | NumCompare | NumDivUnchecked | NumRemUnchecked | NumPow
+        | NumPowInt => arena.alloc_slice_copy(&[irrelevant, irrelevant]),
 
         NumAbs | NumNeg | NumSin | NumCos | NumSqrtUnchecked | NumRound | NumCeiling | NumFloor
         | NumToFloat | Not => arena.alloc_slice_copy(&[irrelevant]),