Fix string pattern matching in mir interpreter

crates/hir-ty/src/chalk_ext.rs

@@ -22,6 +22,7 @@ use crate::{
 pub trait TyExt {
     fn is_unit(&self) -> bool;
     fn is_integral(&self) -> bool;
+    fn is_scalar(&self) -> bool;
     fn is_floating_point(&self) -> bool;
     fn is_never(&self) -> bool;
     fn is_unknown(&self) -> bool;
@@ -68,6 +69,10 @@ impl TyExt for Ty {
         )
     }
 
+    fn is_scalar(&self) -> bool {
+        matches!(self.kind(Interner), TyKind::Scalar(_))
+    }
+
     fn is_floating_point(&self) -> bool {
         matches!(
             self.kind(Interner),

crates/hir-ty/src/consteval/tests.rs

@@ -179,6 +179,7 @@ fn casts() {
         "#,
         4,
     );
+    check_number(r#"const GOAL: i32 = -12i8 as i32"#, -12);
 }
 
 #[test]
@@ -1034,16 +1035,18 @@ fn pattern_matching_literal() {
     );
     check_number(
         r#"
-    const fn f(x: &str) -> u8 {
+    const fn f(x: &str) -> i32 {
         match x {
-            "foo" => 1,
-            "bar" => 10,
-            _ => 100,
+            "f" => 1,
+            "foo" => 10,
+            "" => 100,
+            "bar" => 1000,
+            _ => 10000,
         }
     }
-    const GOAL: u8 = f("foo") + f("bar");
+    const GOAL: i32 = f("f") + f("foo") * 2 + f("") * 3 + f("bar") * 4;
         "#,
-        11,
+        4321,
     );
 }
 

crates/hir-ty/src/mir/eval.rs

@@ -17,6 +17,7 @@ use hir_expand::InFile;
 use intern::Interned;
 use la_arena::ArenaMap;
 use rustc_hash::{FxHashMap, FxHashSet};
+use stdx::never;
 use syntax::{SyntaxNodePtr, TextRange};
 use triomphe::Arc;
 
@@ -896,7 +897,7 @@ impl Evaluator<'_> {
                     Owned(c)
                 }
             }
-            Rvalue::CheckedBinaryOp(op, lhs, rhs) => {
+            Rvalue::CheckedBinaryOp(op, lhs, rhs) => 'binary_op: {
                 let lc = self.eval_operand(lhs, locals)?;
                 let rc = self.eval_operand(rhs, locals)?;
                 let mut lc = lc.get(&self)?;
@@ -905,10 +906,17 @@ impl Evaluator<'_> {
                 while let TyKind::Ref(_, _, z) = ty.kind(Interner) {
                     ty = z.clone();
                     let size = if ty.kind(Interner) == &TyKind::Str {
-                        let ns = from_bytes!(usize, &lc[self.ptr_size()..self.ptr_size() * 2]);
+                        if *op != BinOp::Eq {
+                            never!("Only eq is builtin for `str`");
+                        }
+                        let ls = from_bytes!(usize, &lc[self.ptr_size()..self.ptr_size() * 2]);
+                        let rs = from_bytes!(usize, &rc[self.ptr_size()..self.ptr_size() * 2]);
+                        if ls != rs {
+                            break 'binary_op Owned(vec![0]);
+                        }
                         lc = &lc[..self.ptr_size()];
                         rc = &rc[..self.ptr_size()];
-                        ns
+                        ls
                     } else {
                         self.size_of_sized(&ty, locals, "operand of binary op")?
                     };
@@ -1200,8 +1208,15 @@ impl Evaluator<'_> {
                 CastKind::IntToInt
                 | CastKind::PointerExposeAddress
                 | CastKind::PointerFromExposedAddress => {
-                    // FIXME: handle signed cast
-                    let current = pad16(self.eval_operand(operand, locals)?.get(&self)?, false);
+                    let current_ty = self.operand_ty(operand, locals)?;
+                    let is_signed = match current_ty.kind(Interner) {
+                        TyKind::Scalar(s) => match s {
+                            chalk_ir::Scalar::Int(_) => true,
+                            _ => false,
+                        },
+                        _ => false,
+                    };
+                    let current = pad16(self.eval_operand(operand, locals)?.get(&self)?, is_signed);
                     let dest_size =
                         self.size_of_sized(target_ty, locals, "destination of int to int cast")?;
                     Owned(current[0..dest_size].to_vec())

crates/hir-ty/src/mir/eval/shim.rs

@@ -238,6 +238,22 @@ impl Evaluator<'_> {
         _span: MirSpan,
     ) -> Result<()> {
         match as_str {
+            "memcmp" => {
+                let [ptr1, ptr2, size] = args else {
+                    return Err(MirEvalError::TypeError("memcmp args are not provided"));
+                };
+                let addr1 = Address::from_bytes(ptr1.get(self)?)?;
+                let addr2 = Address::from_bytes(ptr2.get(self)?)?;
+                let size = from_bytes!(usize, size.get(self)?);
+                let slice1 = self.read_memory(addr1, size)?;
+                let slice2 = self.read_memory(addr2, size)?;
+                let r: i128 = match slice1.cmp(slice2) {
+                    cmp::Ordering::Less => -1,
+                    cmp::Ordering::Equal => 0,
+                    cmp::Ordering::Greater => 1,
+                };
+                destination.write_from_bytes(self, &r.to_le_bytes()[..destination.size])
+            }
             "write" => {
                 let [fd, ptr, len] = args else {
                     return Err(MirEvalError::TypeError("libc::write args are not provided"));

crates/hir-ty/src/mir/eval/tests.rs

@@ -228,6 +228,39 @@ fn main() {
     );
 }
 
+#[test]
+fn memcmp() {
+    check_pass(
+        r#"
+//- minicore: slice, coerce_unsized, index
+
+fn should_not_reach() -> bool {
+    _ // FIXME: replace this function with panic when that works
+}
+
+extern "C" {
+    fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
+}
+
+fn my_cmp(x: &[u8], y: &[u8]) -> i32 {
+    memcmp(x as *const u8, y as *const u8, x.len())
+}
+
+fn main() {
+    if my_cmp(&[1, 2, 3], &[1, 2, 3]) != 0 {
+        should_not_reach();
+    }
+    if my_cmp(&[1, 20, 3], &[1, 2, 3]) <= 0 {
+        should_not_reach();
+    }
+    if my_cmp(&[1, 2, 3], &[1, 20, 3]) >= 0 {
+        should_not_reach();
+    }
+}
+    "#,
+    );
+}
+
 #[test]
 fn unix_write_stdout() {
     check_pass_and_stdio(

crates/hir-ty/src/mir/lower.rs

@@ -829,7 +829,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         op,
                         BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) | BinaryOp::Assignment { op: Some(ArithOp::Shl | ArithOp::Shr) }
                     );
-                    lhs_ty.as_builtin().is_some() && rhs_ty.as_builtin().is_some() && (lhs_ty == rhs_ty || builtin_inequal_impls)
+                    lhs_ty.is_scalar() && rhs_ty.is_scalar() && (lhs_ty == rhs_ty || builtin_inequal_impls)
                 };
                 if !is_builtin {
                     if let Some((func_id, generic_args)) = self.infer.method_resolution(expr_id) {