Enable stubbing and function contracts for primitive types

kani-compiler/src/kani_middle/resolve/type_resolution.rs

@@ -0,0 +1,202 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//! This module contains code used for resolve type / trait names
+
+use crate::kani_middle::resolve::{resolve_path, validate_kind, ResolveError};
+use quote::ToTokens;
+use rustc_hir::def::DefKind;
+use rustc_middle::ty::TyCtxt;
+use rustc_smir::rustc_internal;
+use rustc_span::def_id::LocalDefId;
+use stable_mir::mir::Mutability;
+use stable_mir::ty::{FloatTy, IntTy, Region, RegionKind, RigidTy, Ty, UintTy};
+use std::str::FromStr;
+use strum_macros::{EnumString, IntoStaticStr};
+use syn::{Expr, ExprLit, Lit, Type, TypePath};
+use tracing::{debug, debug_span};
+
+/// Attempts to resolve a type from a type expression.
+pub fn resolve_ty<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    current_module: LocalDefId,
+    typ: &syn::Type,
+) -> Result<Ty, ResolveError<'tcx>> {
+    let _span = debug_span!("resolve_ty", ?typ).entered();
+    debug!(?typ, ?current_module, "resolve_ty");
+    let unsupported = |kind: &'static str| Err(ResolveError::UnsupportedPath { kind });
+    let invalid = |kind: &'static str| {
+        Err(ResolveError::InvalidPath {
+            msg: format!("Expected a type, but found {kind} `{}`", typ.to_token_stream()),
+        })
+    };
+    #[warn(non_exhaustive_omitted_patterns)]
+    match typ {
+        Type::Path(TypePath { qself, path }) => {
+            assert_eq!(*qself, None, "Unexpected qualified path");
+            if let Some(primitive) =
+                path.get_ident().and_then(|ident| PrimitiveIdent::from_str(&ident.to_string()).ok())
+            {
+                Ok(primitive.into())
+            } else {
+                let def_id = resolve_path(tcx, current_module, path)?;
+                validate_kind!(
+                    tcx,
+                    def_id,
+                    "type",
+                    DefKind::Struct | DefKind::Union | DefKind::Enum
+                )?;
+                Ok(rustc_internal::stable(tcx.type_of(def_id)).value)
+            }
+        }
+        Type::Array(array) => {
+            let elem_ty = resolve_ty(tcx, current_module, &array.elem)?;
+            let len = parse_len(&array.len).map_err(|msg| ResolveError::InvalidPath { msg })?;
+            Ty::try_new_array(elem_ty, len.try_into().unwrap()).map_err(|err| {
+                ResolveError::InvalidPath { msg: format!("Cannot instantiate array. {err}") }
+            })
+        }
+        Type::Paren(inner) => resolve_ty(tcx, current_module, &inner.elem),
+        Type::Ptr(ptr) => {
+            let elem_ty = resolve_ty(tcx, current_module, &ptr.elem)?;
+            let mutability =
+                if ptr.mutability.is_some() { Mutability::Mut } else { Mutability::Not };
+            Ok(Ty::new_ptr(elem_ty, mutability))
+        }
+        Type::Reference(reference) => {
+            let elem_ty = resolve_ty(tcx, current_module, &reference.elem)?;
+            let mutability =
+                if reference.mutability.is_some() { Mutability::Mut } else { Mutability::Not };
+            Ok(Ty::new_ref(Region { kind: RegionKind::ReErased }, elem_ty, mutability))
+        }
+        Type::Slice(slice) => {
+            let elem_ty = resolve_ty(tcx, current_module, &slice.elem)?;
+            Ok(Ty::from_rigid_kind(RigidTy::Slice(elem_ty)))
+        }
+        Type::Tuple(tuple) => {
+            let elems = tuple
+                .elems
+                .iter()
+                .map(|elem| resolve_ty(tcx, current_module, &elem))
+                .collect::<Result<Vec<_>, _>>()?;
+            Ok(Ty::new_tuple(&elems))
+        }
+        Type::Never(_) => Ok(Ty::from_rigid_kind(RigidTy::Never)),
+        Type::BareFn(_) => unsupported("bare function"),
+        Type::Macro(_) => invalid("macro"),
+        Type::Group(_) => invalid("group paths"),
+        Type::ImplTrait(_) => invalid("trait impl paths"),
+        Type::Infer(_) => invalid("inferred paths"),
+        Type::TraitObject(_) => invalid("trait object paths"),
+        Type::Verbatim(_) => unsupported("unknown paths"),
+        _ => {
+            unreachable!()
+        }
+    }
+}
+
+/// Enumeration of existing primitive types that are not parametric.
+#[derive(Copy, Clone, Debug, Eq, PartialEq, IntoStaticStr, EnumString)]
+#[strum(serialize_all = "lowercase")]
+pub(super) enum PrimitiveIdent {
+    Bool,
+    Char,
+    F16,
+    F32,
+    F64,
+    F128,
+    I8,
+    I16,
+    I32,
+    I64,
+    I128,
+    Isize,
+    Str,
+    U8,
+    U16,
+    U32,
+    U64,
+    U128,
+    Usize,
+}
+
+/// Convert a primitive ident into a primitive `Ty`.
+impl From<PrimitiveIdent> for Ty {
+    fn from(value: PrimitiveIdent) -> Self {
+        match value {
+            PrimitiveIdent::Bool => Ty::bool_ty(),
+            PrimitiveIdent::Char => Ty::from_rigid_kind(RigidTy::Char),
+            PrimitiveIdent::F16 => Ty::from_rigid_kind(RigidTy::Float(FloatTy::F16)),
+            PrimitiveIdent::F32 => Ty::from_rigid_kind(RigidTy::Float(FloatTy::F32)),
+            PrimitiveIdent::F64 => Ty::from_rigid_kind(RigidTy::Float(FloatTy::F64)),
+            PrimitiveIdent::F128 => Ty::from_rigid_kind(RigidTy::Float(FloatTy::F128)),
+            PrimitiveIdent::I8 => Ty::signed_ty(IntTy::I8),
+            PrimitiveIdent::I16 => Ty::signed_ty(IntTy::I16),
+            PrimitiveIdent::I32 => Ty::signed_ty(IntTy::I32),
+            PrimitiveIdent::I64 => Ty::signed_ty(IntTy::I64),
+            PrimitiveIdent::I128 => Ty::signed_ty(IntTy::I128),
+            PrimitiveIdent::Isize => Ty::signed_ty(IntTy::Isize),
+            PrimitiveIdent::Str => Ty::from_rigid_kind(RigidTy::Str),
+            PrimitiveIdent::U8 => Ty::unsigned_ty(UintTy::U8),
+            PrimitiveIdent::U16 => Ty::unsigned_ty(UintTy::U16),
+            PrimitiveIdent::U32 => Ty::unsigned_ty(UintTy::U32),
+            PrimitiveIdent::U64 => Ty::unsigned_ty(UintTy::U64),
+            PrimitiveIdent::U128 => Ty::unsigned_ty(UintTy::U128),
+            PrimitiveIdent::Usize => Ty::unsigned_ty(UintTy::Usize),
+        }
+    }
+}
+
+/// Checks if a Path segment represents a primitive.
+///
+/// Note that this function will return false for expressions that cannot be parsed as a type.
+pub(super) fn is_primitive<T>(path: &T) -> bool
+where
+    T: ToTokens,
+{
+    let token = path.to_token_stream();
+    let Ok(typ) = syn::parse2(token) else { return false };
+    is_type_primitive(&typ)
+}
+
+/// Checks if a type is a primitive including composite ones.
+pub(super) fn is_type_primitive(typ: &syn::Type) -> bool {
+    #[warn(non_exhaustive_omitted_patterns)]
+    match typ {
+        Type::Array(_)
+        | Type::Ptr(_)
+        | Type::Reference(_)
+        | Type::Slice(_)
+        | Type::Never(_)
+        | Type::Tuple(_) => true,
+        Type::Path(TypePath { qself: Some(qself), path }) => {
+            path.segments.is_empty() && is_type_primitive(&qself.ty)
+        }
+        Type::Path(TypePath { qself: None, path }) => path
+            .get_ident()
+            .map_or(false, |ident| PrimitiveIdent::from_str(&ident.to_string()).is_ok()),
+        Type::BareFn(_)
+        | Type::Group(_)
+        | Type::ImplTrait(_)
+        | Type::Infer(_)
+        | Type::Macro(_)
+        | Type::Paren(_)
+        | Type::TraitObject(_)
+        | Type::Verbatim(_) => false,
+        _ => {
+            unreachable!()
+        }
+    }
+}
+
+/// Parse the length of the array.
+/// We currently only support a constant length.
+fn parse_len(len: &Expr) -> Result<usize, String> {
+    if let Expr::Lit(ExprLit { lit: Lit::Int(lit), .. }) = len {
+        if matches!(lit.suffix(), "" | "usize")
+            && let Ok(val) = usize::from_str(lit.base10_digits())
+        {
+            return Ok(val);
+        }
+    }
+    Err(format!("Expected a `usize` constant, but found `{}`", len.to_token_stream()))
+}

tests/kani/Stubbing/StubPrimitives/fixme_stub_lowered_methods.rs

@@ -0,0 +1,26 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// kani-flags: -Z stubbing
+
+//! Kani supports stubbing of most primitive methods, however, some methods, such as len, may be
+//! lowered to an Rvalue.
+
+/// Check that we can stub slices methods
+pub mod slices_check {
+    #[derive(kani::Arbitrary)]
+    pub struct MyStruct(u8, i32);
+
+    pub fn stub_len_is_10<T>(_: &[T]) -> usize {
+        10
+    }
+
+    // This fails since `<[T]>::len` is lowered to `Rvalue::Len`.
+    #[kani::proof]
+    #[kani::stub(<[MyStruct]>::len, stub_len_is_10)]
+    pub fn check_stub_len_is_10() {
+        let input: [MyStruct; 5] = kani::any();
+        let slice = kani::slice::any_slice_of_array(&input);
+        assert_eq!(slice.len(), 10);
+    }
+}

tests/kani/Stubbing/StubPrimitives/stub_char_methods.rs

@@ -0,0 +1,18 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// kani-flags: -Z stubbing
+//
+//! This tests that we can correctly stub char functions.
+/// Check that we can stub is_ascii from `char`.
+pub fn stub_is_ascii_true(_: &char) -> bool {
+    true
+}
+
+/// Check stubbing by directly calling `str::is_ascii`
+#[kani::proof]
+#[kani::stub(char::is_ascii, stub_is_ascii_true)]
+pub fn check_stub_is_ascii() {
+    let input: char = kani::any();
+    assert!(input.is_ascii());
+}

tests/kani/Stubbing/StubPrimitives/stub_int_methods.rs

@@ -0,0 +1,39 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// kani-flags: -Z stubbing
+//
+//! This tests that we can correctly stub integer types functions.
+
+/// Generate stub and harness for count_ones method on integers.
+macro_rules! stub_count_ones {
+    ($ty:ty, $harness:ident, $stub:ident) => {
+        // Stub that always returns 0.
+        pub fn $stub(_: $ty) -> u32 {
+            0
+        }
+
+        // Harness
+        #[kani::proof]
+        #[kani::stub($ty::count_ones, $stub)]
+        pub fn $harness() {
+            let input = kani::any();
+            let ones = <$ty>::count_ones(input);
+            assert_eq!(ones, 0);
+        }
+    };
+}
+
+stub_count_ones!(u8, u8_count_ones, stub_u8_count_ones);
+stub_count_ones!(u16, u16_count_ones, stub_u16_count_ones);
+stub_count_ones!(u32, u32_count_ones, stub_u32_count_ones);
+stub_count_ones!(u64, u64_count_ones, stub_u64_count_ones);
+stub_count_ones!(u128, u128_count_ones, stub_u128_count_ones);
+stub_count_ones!(usize, usize_count_ones, stub_usize_count_ones);
+
+stub_count_ones!(i8, i8_count_ones, stub_i8_count_ones);
+stub_count_ones!(i16, i16_count_ones, stub_i16_count_ones);
+stub_count_ones!(i32, i32_count_ones, stub_i32_count_ones);
+stub_count_ones!(i64, i64_count_ones, stub_i64_count_ones);
+stub_count_ones!(i128, i128_count_ones, stub_i128_count_ones);
+stub_count_ones!(isize, isize_count_ones, stub_isize_count_ones);

tests/kani/Stubbing/StubPrimitives/stub_ptr_methods.rs

@@ -0,0 +1,38 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// kani-flags: -Z stubbing
+//
+//! This tests that we can correctly stub methods from raw pointer types.
+
+pub fn stub_len_is_10<T>(_: *const [T]) -> usize {
+    10
+}
+
+pub fn stub_mut_len_is_0<T>(_: *mut [T]) -> usize {
+    0
+}
+
+#[kani::proof]
+#[kani::stub(<*const [u8]>::len, stub_len_is_10)]
+#[kani::stub(<*mut [u8]>::len, stub_mut_len_is_0)]
+pub fn check_stub_len_raw_ptr() {
+    let mut input: [u8; 5] = kani::any();
+    let mut_ptr = &mut input as *mut [u8];
+    let ptr = &input as *const [u8];
+    assert_eq!(mut_ptr.len(), 0);
+    assert_eq!(ptr.len(), 10);
+}
+
+pub fn stub_is_always_null<T>(_: *const T) -> bool {
+    true
+}
+
+// Fix-me: Option doesn't seem to work without the fully qualified path.
+#[kani::proof]
+#[kani::stub(<*const std::option::Option>::is_null, stub_is_always_null)]
+pub fn check_stub_is_null() {
+    let input: Option<char> = kani::any();
+    let ptr = &input as *const Option<char>;
+    assert!(unsafe { ptr.is_null() });
+}

tests/kani/Stubbing/StubPrimitives/stub_slice_methods.rs

@@ -0,0 +1,37 @@
+// Copyright Kani Contributors
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// kani-flags: -Z stubbing
+//
+//! This tests that we can correctly stub slices and string slices functions.
+
+/// Check that we can stub str::is_ascii
+pub mod str_check {
+    pub fn stub_is_ascii_false(_: &str) -> bool {
+        false
+    }
+
+    #[kani::proof]
+    #[kani::stub(str::is_ascii, stub_is_ascii_false)]
+    pub fn check_stub_is_ascii() {
+        let input = "is_ascii";
+        assert!(!input.is_ascii());
+    }
+}
+
+/// Check that we can stub slices
+pub mod slices_check {
+    #[derive(kani::Arbitrary, Ord, PartialOrd, Copy, Clone, PartialEq, Eq)]
+    pub struct MyStruct(u8, i32);
+
+    pub fn stub_sort_noop<T>(_: &mut [T]) {}
+
+    #[kani::proof]
+    #[kani::stub(<[MyStruct]>::sort, stub_sort_noop)]
+    pub fn check_stub_sort_noop() {
+        let mut input: [MyStruct; 5] = kani::any();
+        let copy = input.clone();
+        input.sort();
+        assert_eq!(input, copy);
+    }
+}