Implement BeginPanic for mir eval

crates/hir-ty/src/chalk_ext.rs

@@ -27,6 +27,7 @@ pub trait TyExt {
     fn is_scalar(&self) -> bool;
     fn is_floating_point(&self) -> bool;
     fn is_never(&self) -> bool;
+    fn is_str(&self) -> bool;
     fn is_unknown(&self) -> bool;
     fn contains_unknown(&self) -> bool;
     fn is_ty_var(&self) -> bool;
@@ -87,6 +88,10 @@ impl TyExt for Ty {
         matches!(self.kind(Interner), TyKind::Never)
     }
 
+    fn is_str(&self) -> bool {
+        matches!(self.kind(Interner), TyKind::Str)
+    }
+
     fn is_unknown(&self) -> bool {
         matches!(self.kind(Interner), TyKind::Error)
     }

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

@@ -1138,7 +1138,7 @@ impl Evaluator<'_> {
                 let mut ty = self.operand_ty(lhs, locals)?;
                 while let TyKind::Ref(_, _, z) = ty.kind(Interner) {
                     ty = z.clone();
-                    let size = if ty.kind(Interner) == &TyKind::Str {
+                    let size = if ty.is_str() {
                         if *op != BinOp::Eq {
                             never!("Only eq is builtin for `str`");
                         }

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

@@ -132,9 +132,7 @@ impl Evaluator<'_> {
             return Ok(true);
         }
         if let Some(it) = self.detect_lang_function(def) {
-            let arg_bytes =
-                args.iter().map(|it| Ok(it.get(self)?.to_owned())).collect::<Result<Vec<_>>>()?;
-            let result = self.exec_lang_item(it, generic_args, &arg_bytes, locals, span)?;
+            let result = self.exec_lang_item(it, generic_args, args, locals, span)?;
             destination.write_from_bytes(self, &result)?;
             return Ok(true);
         }
@@ -333,18 +331,52 @@ impl Evaluator<'_> {
         &mut self,
         it: LangItem,
         generic_args: &Substitution,
-        args: &[Vec<u8>],
+        args: &[IntervalAndTy],
         locals: &Locals,
         span: MirSpan,
     ) -> Result<Vec<u8>> {
         use LangItem::*;
         let mut args = args.iter();
         match it {
-            BeginPanic => Err(MirEvalError::Panic("<unknown-panic-payload>".to_owned())),
+            BeginPanic => {
+                let mut arg = args
+                    .next()
+                    .ok_or(MirEvalError::InternalError(
+                        "argument of BeginPanic is not provided".into(),
+                    ))?
+                    .clone();
+                while let TyKind::Ref(_, _, ty) = arg.ty.kind(Interner) {
+                    if ty.is_str() {
+                        let (pointee, metadata) = arg.interval.get(self)?.split_at(self.ptr_size());
+                        let len = from_bytes!(usize, metadata);
+
+                        return {
+                            Err(MirEvalError::Panic(
+                                std::str::from_utf8(
+                                    self.read_memory(Address::from_bytes(pointee)?, len)?,
+                                )
+                                .unwrap()
+                                .to_owned(),
+                            ))
+                        };
+                    }
+                    let size = self.size_of_sized(&ty, locals, "begin panic arg")?;
+                    let pointee = arg.interval.get(self)?;
+                    arg = IntervalAndTy {
+                        interval: Interval::new(Address::from_bytes(pointee)?, size),
+                        ty: ty.clone(),
+                    };
+                }
+                Err(MirEvalError::Panic(format!(
+                    "unknown-panic-payload: {:?}",
+                    arg.ty.kind(Interner)
+                )))
+            }
             SliceLen => {
                 let arg = args.next().ok_or(MirEvalError::InternalError(
                     "argument of <[T]>::len() is not provided".into(),
                 ))?;
+                let arg = arg.get(self)?;
                 let ptr_size = arg.len() / 2;
                 Ok(arg[ptr_size..].into())
             }
@@ -358,6 +390,7 @@ impl Evaluator<'_> {
                 let arg = args.next().ok_or(MirEvalError::InternalError(
                     "argument of drop_in_place is not provided".into(),
                 ))?;
+                let arg = arg.interval.get(self)?.to_owned();
                 self.run_drop_glue_deep(
                     ty.clone(),
                     locals,

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

@@ -104,7 +104,6 @@ fn main() {
 }
     "#,
     );
-    panic!("a");
 }
 
 #[test]