Implement BeginPanic handling in const eval

crates/hir-def/src/body/lower.rs

@@ -1869,42 +1869,45 @@ impl ExprCollector<'_> {
     ) -> ExprId {
         match count {
             Some(FormatCount::Literal(n)) => {
-                match LangItem::FormatCount.ty_rel_path(self.db, self.krate, name![Is]) {
-                    Some(count_is) => {
-                        let count_is = self.alloc_expr_desugared(Expr::Path(count_is));
-                        let args = self.alloc_expr_desugared(Expr::Literal(Literal::Uint(
-                            *n as u128,
-                            Some(BuiltinUint::Usize),
-                        )));
-                        self.alloc_expr_desugared(Expr::Call {
-                            callee: count_is,
-                            args: Box::new([args]),
-                            is_assignee_expr: false,
-                        })
-                    }
-                    None => self.missing_expr(),
-                }
+                let args = self.alloc_expr_desugared(Expr::Literal(Literal::Uint(
+                    *n as u128,
+                    Some(BuiltinUint::Usize),
+                )));
+                let count_is =
+                    match LangItem::FormatCount.ty_rel_path(self.db, self.krate, name![Is]) {
+                        Some(count_is) => self.alloc_expr_desugared(Expr::Path(count_is)),
+                        None => self.missing_expr(),
+                    };
+                self.alloc_expr_desugared(Expr::Call {
+                    callee: count_is,
+                    args: Box::new([args]),
+                    is_assignee_expr: false,
+                })
             }
             Some(FormatCount::Argument(arg)) => {
                 if let Ok(arg_index) = arg.index {
                     let (i, _) = argmap.insert_full((arg_index, ArgumentType::Usize));
 
-                    match LangItem::FormatCount.ty_rel_path(self.db, self.krate, name![Param]) {
-                        Some(count_param) => {
-                            let count_param = self.alloc_expr_desugared(Expr::Path(count_param));
-                            let args = self.alloc_expr_desugared(Expr::Literal(Literal::Uint(
-                                i as u128,
-                                Some(BuiltinUint::Usize),
-                            )));
-                            self.alloc_expr_desugared(Expr::Call {
-                                callee: count_param,
-                                args: Box::new([args]),
-                                is_assignee_expr: false,
-                            })
-                        }
+                    let args = self.alloc_expr_desugared(Expr::Literal(Literal::Uint(
+                        i as u128,
+                        Some(BuiltinUint::Usize),
+                    )));
+                    let count_param = match LangItem::FormatCount.ty_rel_path(
+                        self.db,
+                        self.krate,
+                        name![Param],
+                    ) {
+                        Some(count_param) => self.alloc_expr_desugared(Expr::Path(count_param)),
                         None => self.missing_expr(),
-                    }
+                    };
+                    self.alloc_expr_desugared(Expr::Call {
+                        callee: count_param,
+                        args: Box::new([args]),
+                        is_assignee_expr: false,
+                    })
                 } else {
+                    // FIXME: This drops arg causing it to potentially not be resolved/type checked
+                    // when typing?
                     self.missing_expr()
                 }
             }
@@ -1925,7 +1928,8 @@ impl ExprCollector<'_> {
     fn make_argument(&mut self, arg: ExprId, ty: ArgumentType) -> ExprId {
         use ArgumentType::*;
         use FormatTrait::*;
-        match LangItem::FormatArgument.ty_rel_path(
+
+        let new_fn = match LangItem::FormatArgument.ty_rel_path(
             self.db,
             self.krate,
             match ty {
@@ -1941,16 +1945,14 @@ impl ExprCollector<'_> {
                 Usize => name![from_usize],
             },
         ) {
-            Some(new_fn) => {
-                let new_fn = self.alloc_expr_desugared(Expr::Path(new_fn));
-                self.alloc_expr_desugared(Expr::Call {
-                    callee: new_fn,
-                    args: Box::new([arg]),
-                    is_assignee_expr: false,
-                })
-            }
+            Some(new_fn) => self.alloc_expr_desugared(Expr::Path(new_fn)),
             None => self.missing_expr(),
-        }
+        };
+        self.alloc_expr_desugared(Expr::Call {
+            callee: new_fn,
+            args: Box::new([arg]),
+            is_assignee_expr: false,
+        })
     }
     // endregion: format
 }

crates/hir-def/src/body/tests.rs

@@ -318,18 +318,20 @@ fn f() {
 
     expect![[r#"
         fn f() {
-            $crate::panicking::panic_fmt(
-                builtin#lang(Arguments::new_v1_formatted)(
-                    &[
-                        "cc",
-                    ],
-                    &[],
-                    &[],
-                    unsafe {
-                        builtin#lang(UnsafeArg::new)()
-                    },
-                ),
-            );
+            {
+                $crate::panicking::panic_fmt(
+                    builtin#lang(Arguments::new_v1_formatted)(
+                        &[
+                            "cc",
+                        ],
+                        &[],
+                        &[],
+                        unsafe {
+                            builtin#lang(UnsafeArg::new)()
+                        },
+                    ),
+                );
+            };
         }"#]]
     .assert_eq(&body.pretty_print(&db, def))
 }

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

@@ -428,6 +428,17 @@ impl MirEvalError {
         }
         Ok(())
     }
+
+    pub fn is_panic(&self) -> Option<&str> {
+        let mut err = self;
+        while let MirEvalError::InFunction(e, _) = err {
+            err = e;
+        }
+        match err {
+            MirEvalError::Panic(msg) => Some(msg),
+            _ => None,
+        }
+    }
 }
 
 impl std::fmt::Debug for MirEvalError {
@@ -1138,7 +1149,7 @@ 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

@@ -49,6 +49,7 @@ impl Evaluator<'_> {
         if self.not_special_fn_cache.borrow().contains(&def) {
             return Ok(false);
         }
+
         let function_data = self.db.function_data(def);
         let is_intrinsic = match &function_data.abi {
             Some(abi) => *abi == Interned::new_str("rust-intrinsic"),
@@ -131,9 +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);
         }
@@ -311,35 +310,73 @@ impl Evaluator<'_> {
 
     fn detect_lang_function(&self, def: FunctionId) -> Option<LangItem> {
         use LangItem::*;
-        let candidate = self.db.lang_attr(def.into())?;
+        let attrs = self.db.attrs(def.into());
+
+        if attrs.by_key("rustc_const_panic_str").exists() {
+            // `#[rustc_const_panic_str]` is treated like `lang = "begin_panic"` by rustc CTFE.
+            return Some(LangItem::BeginPanic);
+        }
+
+        let candidate = attrs.by_key("lang").string_value().and_then(LangItem::from_str)?;
         // We want to execute these functions with special logic
         // `PanicFmt` is not detected here as it's redirected later.
         if [BeginPanic, SliceLen, DropInPlace].contains(&candidate) {
             return Some(candidate);
         }
-        if self.db.attrs(def.into()).by_key("rustc_const_panic_str").exists() {
-            // `#[rustc_const_panic_str]` is treated like `lang = "begin_panic"` by rustc CTFE.
-            return Some(LangItem::BeginPanic);
-        }
+
         None
     }
 
     fn exec_lang_item(
         &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())
             }
@@ -353,6 +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

@@ -31,6 +31,7 @@ fn eval_main(db: &TestDB, file_id: FileId) -> Result<(String, String), MirEvalEr
             db.trait_environment(func_id.into()),
         )
         .map_err(|e| MirEvalError::MirLowerError(func_id, e))?;
+
     let (result, output) = interpret_mir(db, body, false, None);
     result?;
     Ok((output.stdout().into_owned(), output.stderr().into_owned()))
@@ -72,6 +73,13 @@ fn check_pass_and_stdio(ra_fixture: &str, expected_stdout: &str, expected_stderr
     }
 }
 
+fn check_panic(ra_fixture: &str, expected_panic: &str) {
+    let (db, file_ids) = TestDB::with_many_files(ra_fixture);
+    let file_id = *file_ids.last().unwrap();
+    let e = eval_main(&db, file_id).unwrap_err();
+    assert_eq!(e.is_panic().unwrap_or_else(|| panic!("unexpected error: {:?}", e)), expected_panic);
+}
+
 #[test]
 fn function_with_extern_c_abi() {
     check_pass(
@@ -87,6 +95,43 @@ fn main() {
     );
 }
 
+#[test]
+fn panic_fmt() {
+    // panic!
+    // -> panic_2021 (builtin macro redirection)
+    //   -> #[lang = "panic_fmt"] core::panicking::panic_fmt (hooked by CTFE for redirection)
+    //   -> core::panicking::const_panic_fmt
+    //     -> #[rustc_const_panic_str] core::panicking::panic_display (hooked by CTFE for builtin panic)
+    //       -> Err(ConstEvalError::Panic)
+    check_panic(
+        r#"
+//- minicore: fmt, panic
+fn main() {
+    panic!("hello, world!");
+}
+    "#,
+        "hello, world!",
+    );
+}
+
+#[test]
+fn panic_display() {
+    // panic!
+    // -> panic_2021 (builtin macro redirection)
+    //   -> #[rustc_const_panic_str] core::panicking::panic_display (hooked by CTFE for builtin panic)
+    //     -> Err(ConstEvalError::Panic)
+    check_panic(
+        r#"
+//- minicore: fmt, panic
+
+fn main() {
+    panic!("{}", "hello, world!");
+}
+    "#,
+        "hello, world!",
+    );
+}
+
 #[test]
 fn drop_basic() {
     check_pass(

crates/ide-diagnostics/src/tests.rs

@@ -293,6 +293,7 @@ fn minicore_smoke_test() {
         // This should be ignored since we conditionally remove code which creates single item use with braces
         config.disabled.insert("unused_braces".to_owned());
         config.disabled.insert("unused_variables".to_owned());
+        config.disabled.insert("remove-unnecessary-else".to_owned());
         check_diagnostics_with_config(config, &source);
     }
 

crates/ide/src/hover/tests.rs

@@ -7864,8 +7864,8 @@ impl Iterator for S {
                                 file_id: FileId(
                                     1,
                                 ),
-                                full_range: 6290..6498,
-                                focus_range: 6355..6361,
+                                full_range: 7791..7999,
+                                focus_range: 7856..7862,
                                 name: "Future",
                                 kind: Trait,
                                 container_name: "future",
@@ -7878,8 +7878,8 @@ impl Iterator for S {
                                 file_id: FileId(
                                     1,
                                 ),
-                                full_range: 7128..7594,
-                                focus_range: 7172..7180,
+                                full_range: 8629..9095,
+                                focus_range: 8673..8681,
                                 name: "Iterator",
                                 kind: Trait,
                                 container_name: "iterator",

crates/ide/src/syntax_highlighting/test_data/highlight_default_library.html

@@ -49,5 +49,5 @@
 
 <span class="keyword">fn</span> <span class="function declaration">main</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
     <span class="keyword">let</span> <span class="variable declaration">foo</span> <span class="operator">=</span> <span class="enum_variant default_library library">Some</span><span class="parenthesis">(</span><span class="numeric_literal">92</span><span class="parenthesis">)</span><span class="semicolon">;</span>
-    <span class="keyword">let</span> <span class="variable declaration">nums</span> <span class="operator">=</span> <span class="module default_library library">iter</span><span class="operator">::</span><span class="function default_library library">repeat</span><span class="parenthesis">(</span><span class="variable">foo</span><span class="operator">.</span><span class="method consuming default_library library">unwrap</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="keyword">let</span> <span class="variable declaration">nums</span> <span class="operator">=</span> <span class="module default_library library">iter</span><span class="operator">::</span><span class="function default_library library">repeat</span><span class="parenthesis">(</span><span class="variable">foo</span><span class="operator">.</span><span class="method default_library library">unwrap</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="parenthesis">)</span><span class="semicolon">;</span>
 <span class="brace">}</span></code></pre>