7 files changed, 120 insertions, 50 deletions

diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 4d52904b9..a7d0f5b1f 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -1,10 +1,10 @@
 //! Builtin macro
 use crate::{
     db::AstDatabase, name, quote, AstId, CrateId, EagerMacroId, LazyMacroId, MacroCallId,
-    MacroDefId, MacroDefKind, TextSize,
+    MacroCallLoc, MacroDefId, MacroDefKind, TextSize,
 };
 
-use base_db::{AnchoredPath, FileId};
+use base_db::{AnchoredPath, Edition, FileId};
 use cfg::CfgExpr;
 use either::Either;
 use mbe::{parse_exprs_with_sep, parse_to_token_tree, ExpandResult};
@@ -111,6 +111,8 @@ register_builtin! {
     (llvm_asm, LlvmAsm) => asm_expand,
     (asm, Asm) => asm_expand,
     (cfg, Cfg) => cfg_expand,
+    (core_panic, CorePanic) => panic_expand,
+    (std_panic, StdPanic) => panic_expand,
 
     EAGER:
     (compile_error, CompileError) => compile_error_expand,
@@ -284,6 +286,25 @@ fn cfg_expand(
     ExpandResult::ok(expanded)
 }
 
+fn panic_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> ExpandResult<tt::Subtree> {
+    let loc: MacroCallLoc = db.lookup_intern_macro(id);
+    // Expand to a macro call `$crate::panic::panic_{edition}`
+    let krate = tt::Ident { text: "$crate".into(), id: tt::TokenId::unspecified() };
+    let mut call = if db.crate_graph()[loc.krate].edition == Edition::Edition2021 {
+        quote!(#krate::panic::panic_2021!)
+    } else {
+        quote!(#krate::panic::panic_2015!)
+    };
+
+    // Pass the original arguments
+    call.token_trees.push(tt::TokenTree::Subtree(tt.clone()));
+    ExpandResult::ok(call)
+}
+
 fn unquote_str(lit: &tt::Literal) -> Option<String> {
     let lit = ast::make::tokens::literal(&lit.to_string());
     let token = ast::String::cast(lit)?;
@@ -469,7 +490,7 @@ fn env_expand(
         // unnecessary diagnostics for eg. `CARGO_PKG_NAME`.
         if key == "OUT_DIR" {
             err = Some(mbe::ExpandError::Other(
-                r#"`OUT_DIR` not set, enable "load out dirs from check" to fix"#.into(),
+                r#"`OUT_DIR` not set, enable "run build scripts" to fix"#.into(),
             ));
         }
 
@@ -563,7 +584,7 @@ mod tests {
                 };
 
                 let args = macro_call.token_tree().unwrap();
-                let parsed_args = mbe::ast_to_token_tree(&args).unwrap().0;
+                let parsed_args = mbe::ast_to_token_tree(&args).0;
                 let call_id = AstId::new(file_id.into(), ast_id_map.ast_id(&macro_call));
 
                 let arg_id = db.intern_eager_expansion({
diff --git a/crates/hir_expand/src/db.rs b/crates/hir_expand/src/db.rs
index fc73e435b..10fe60821 100644
--- a/crates/hir_expand/src/db.rs
+++ b/crates/hir_expand/src/db.rs
@@ -3,9 +3,15 @@
 use std::sync::Arc;
 
 use base_db::{salsa, SourceDatabase};
-use mbe::{ExpandError, ExpandResult, MacroRules};
+use mbe::{ExpandError, ExpandResult, MacroDef, MacroRules};
 use parser::FragmentKind;
-use syntax::{algo::diff, ast::NameOwner, AstNode, GreenNode, Parse, SyntaxKind::*, SyntaxNode};
+use syntax::{
+    algo::diff,
+    ast::{MacroStmts, NameOwner},
+    AstNode, GreenNode, Parse,
+    SyntaxKind::*,
+    SyntaxNode,
+};
 
 use crate::{
     ast_id_map::AstIdMap, hygiene::HygieneFrame, BuiltinDeriveExpander, BuiltinFnLikeExpander,
@@ -22,6 +28,7 @@ const TOKEN_LIMIT: usize = 524288;
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum TokenExpander {
     MacroRules(mbe::MacroRules),
+    MacroDef(mbe::MacroDef),
     Builtin(BuiltinFnLikeExpander),
     BuiltinDerive(BuiltinDeriveExpander),
     ProcMacro(ProcMacroExpander),
@@ -36,6 +43,7 @@ impl TokenExpander {
     ) -> mbe::ExpandResult<tt::Subtree> {
         match self {
             TokenExpander::MacroRules(it) => it.expand(tt),
+            TokenExpander::MacroDef(it) => it.expand(tt),
             TokenExpander::Builtin(it) => it.expand(db, id, tt),
             // FIXME switch these to ExpandResult as well
             TokenExpander::BuiltinDerive(it) => it.expand(db, id, tt).into(),
@@ -51,6 +59,7 @@ impl TokenExpander {
     pub fn map_id_down(&self, id: tt::TokenId) -> tt::TokenId {
         match self {
             TokenExpander::MacroRules(it) => it.map_id_down(id),
+            TokenExpander::MacroDef(it) => it.map_id_down(id),
             TokenExpander::Builtin(..) => id,
             TokenExpander::BuiltinDerive(..) => id,
             TokenExpander::ProcMacro(..) => id,
@@ -60,6 +69,7 @@ impl TokenExpander {
     pub fn map_id_up(&self, id: tt::TokenId) -> (tt::TokenId, mbe::Origin) {
         match self {
             TokenExpander::MacroRules(it) => it.map_id_up(id),
+            TokenExpander::MacroDef(it) => it.map_id_up(id),
             TokenExpander::Builtin(..) => (id, mbe::Origin::Call),
             TokenExpander::BuiltinDerive(..) => (id, mbe::Origin::Call),
             TokenExpander::ProcMacro(..) => (id, mbe::Origin::Call),
@@ -109,7 +119,7 @@ pub fn expand_hypothetical(
     token_to_map: syntax::SyntaxToken,
 ) -> Option<(SyntaxNode, syntax::SyntaxToken)> {
     let macro_file = MacroFile { macro_call_id: actual_macro_call };
-    let (tt, tmap_1) = mbe::syntax_node_to_token_tree(hypothetical_args.syntax()).unwrap();
+    let (tt, tmap_1) = mbe::syntax_node_to_token_tree(hypothetical_args.syntax());
     let range =
         token_to_map.text_range().checked_sub(hypothetical_args.syntax().text_range().start())?;
     let token_id = tmap_1.token_by_range(range)?;
@@ -130,26 +140,34 @@ fn ast_id_map(db: &dyn AstDatabase, file_id: HirFileId) -> Arc<AstIdMap> {
 
 fn macro_def(db: &dyn AstDatabase, id: MacroDefId) -> Option<Arc<(TokenExpander, mbe::TokenMap)>> {
     match id.kind {
-        MacroDefKind::Declarative(ast_id) => {
-            let macro_rules = match ast_id.to_node(db) {
-                syntax::ast::Macro::MacroRules(mac) => mac,
-                syntax::ast::Macro::MacroDef(_) => return None,
-            };
-            let arg = macro_rules.token_tree()?;
-            let (tt, tmap) = mbe::ast_to_token_tree(&arg).or_else(|| {
-                log::warn!("fail on macro_def to token tree: {:#?}", arg);
-                None
-            })?;
-            let rules = match MacroRules::parse(&tt) {
-                Ok(it) => it,
-                Err(err) => {
-                    let name = macro_rules.name().map(|n| n.to_string()).unwrap_or_default();
-                    log::warn!("fail on macro_def parse ({}): {:?} {:#?}", name, err, tt);
-                    return None;
-                }
-            };
-            Some(Arc::new((TokenExpander::MacroRules(rules), tmap)))
-        }
+        MacroDefKind::Declarative(ast_id) => match ast_id.to_node(db) {
+            syntax::ast::Macro::MacroRules(macro_rules) => {
+                let arg = macro_rules.token_tree()?;
+                let (tt, tmap) = mbe::ast_to_token_tree(&arg);
+                let rules = match MacroRules::parse(&tt) {
+                    Ok(it) => it,
+                    Err(err) => {
+                        let name = macro_rules.name().map(|n| n.to_string()).unwrap_or_default();
+                        log::warn!("fail on macro_def parse ({}): {:?} {:#?}", name, err, tt);
+                        return None;
+                    }
+                };
+                Some(Arc::new((TokenExpander::MacroRules(rules), tmap)))
+            }
+            syntax::ast::Macro::MacroDef(macro_def) => {
+                let arg = macro_def.body()?;
+                let (tt, tmap) = mbe::ast_to_token_tree(&arg);
+                let rules = match MacroDef::parse(&tt) {
+                    Ok(it) => it,
+                    Err(err) => {
+                        let name = macro_def.name().map(|n| n.to_string()).unwrap_or_default();
+                        log::warn!("fail on macro_def parse ({}): {:?} {:#?}", name, err, tt);
+                        return None;
+                    }
+                };
+                Some(Arc::new((TokenExpander::MacroDef(rules), tmap)))
+            }
+        },
         MacroDefKind::BuiltIn(expander, _) => {
             Some(Arc::new((TokenExpander::Builtin(expander), mbe::TokenMap::default())))
         }
@@ -178,7 +196,7 @@ fn macro_arg_text(db: &dyn AstDatabase, id: MacroCallId) -> Option<GreenNode> {
 
 fn macro_arg(db: &dyn AstDatabase, id: MacroCallId) -> Option<Arc<(tt::Subtree, mbe::TokenMap)>> {
     let arg = db.macro_arg_text(id)?;
-    let (tt, tmap) = mbe::syntax_node_to_token_tree(&SyntaxNode::new_root(arg))?;
+    let (tt, tmap) = mbe::syntax_node_to_token_tree(&SyntaxNode::new_root(arg));
     Some(Arc::new((tt, tmap)))
 }
 
@@ -340,13 +358,19 @@ fn parse_macro_with_arg(
         None => return ExpandResult { value: None, err: result.err },
     };
 
-    log::debug!("expanded = {}", tt.as_debug_string());
-
     let fragment_kind = to_fragment_kind(db, macro_call_id);
 
+    log::debug!("expanded = {}", tt.as_debug_string());
+    log::debug!("kind = {:?}", fragment_kind);
+
     let (parse, rev_token_map) = match mbe::token_tree_to_syntax_node(&tt, fragment_kind) {
         Ok(it) => it,
         Err(err) => {
+            log::debug!(
+                "failed to parse expanstion to {:?} = {}",
+                fragment_kind,
+                tt.as_debug_string()
+            );
             return ExpandResult::only_err(err);
         }
     };
@@ -362,15 +386,34 @@ fn parse_macro_with_arg(
                     return ExpandResult::only_err(err);
                 }
             };
-
-            if !diff(&node, &call_node.value).is_empty() {
-                ExpandResult { value: Some((parse, Arc::new(rev_token_map))), err: Some(err) }
-            } else {
+            if is_self_replicating(&node, &call_node.value) {
                 return ExpandResult::only_err(err);
+            } else {
+                ExpandResult { value: Some((parse, Arc::new(rev_token_map))), err: Some(err) }
+            }
+        }
+        None => {
+            log::debug!("parse = {:?}", parse.syntax_node().kind());
+            ExpandResult { value: Some((parse, Arc::new(rev_token_map))), err: None }
+        }
+    }
+}
+
+fn is_self_replicating(from: &SyntaxNode, to: &SyntaxNode) -> bool {
+    if diff(from, to).is_empty() {
+        return true;
+    }
+    if let Some(stmts) = MacroStmts::cast(from.clone()) {
+        if stmts.statements().any(|stmt| diff(stmt.syntax(), to).is_empty()) {
+            return true;
+        }
+        if let Some(expr) = stmts.expr() {
+            if diff(expr.syntax(), to).is_empty() {
+                return true;
             }
         }
-        None => ExpandResult { value: Some((parse, Arc::new(rev_token_map))), err: None },
     }
+    false
 }
 
 fn hygiene_frame(db: &dyn AstDatabase, file_id: HirFileId) -> Arc<HygieneFrame> {
@@ -390,21 +433,15 @@ fn to_fragment_kind(db: &dyn AstDatabase, id: MacroCallId) -> FragmentKind {
 
     let parent = match syn.parent() {
         Some(it) => it,
-        None => {
-            // FIXME:
-            // If it is root, which means the parent HirFile
-            // MacroKindFile must be non-items
-            // return expr now.
-            return FragmentKind::Expr;
-        }
+        None => return FragmentKind::Statements,
     };
 
     match parent.kind() {
         MACRO_ITEMS | SOURCE_FILE => FragmentKind::Items,
-        MACRO_STMTS => FragmentKind::Statement,
+        MACRO_STMTS => FragmentKind::Statements,
         ITEM_LIST => FragmentKind::Items,
         LET_STMT => {
-            // FIXME: Handle Pattern
+            // FIXME: Handle LHS Pattern
             FragmentKind::Expr
         }
         EXPR_STMT => FragmentKind::Statements,
diff --git a/crates/hir_expand/src/eager.rs b/crates/hir_expand/src/eager.rs
index 9eedc8461..9705526fa 100644
--- a/crates/hir_expand/src/eager.rs
+++ b/crates/hir_expand/src/eager.rs
@@ -106,7 +106,7 @@ pub fn expand_eager_macro(
     mut diagnostic_sink: &mut dyn FnMut(mbe::ExpandError),
 ) -> Result<EagerMacroId, ErrorEmitted> {
     let parsed_args = diagnostic_sink.option_with(
-        || Some(mbe::ast_to_token_tree(&macro_call.value.token_tree()?)?.0),
+        || Some(mbe::ast_to_token_tree(&macro_call.value.token_tree()?).0),
         || err("malformed macro invocation"),
     )?;
 
@@ -161,7 +161,7 @@ pub fn expand_eager_macro(
 }
 
 fn to_subtree(node: &SyntaxNode) -> Option<tt::Subtree> {
-    let mut subtree = mbe::syntax_node_to_token_tree(node)?.0;
+    let mut subtree = mbe::syntax_node_to_token_tree(node).0;
     subtree.delimiter = None;
     Some(subtree)
 }
diff --git a/crates/hir_expand/src/hygiene.rs b/crates/hir_expand/src/hygiene.rs
index 0e0f7214a..779725629 100644
--- a/crates/hir_expand/src/hygiene.rs
+++ b/crates/hir_expand/src/hygiene.rs
@@ -148,7 +148,7 @@ fn make_hygiene_info(
     let def_offset = loc.def.ast_id().left().and_then(|id| {
         let def_tt = match id.to_node(db) {
             ast::Macro::MacroRules(mac) => mac.token_tree()?.syntax().text_range().start(),
-            ast::Macro::MacroDef(_) => return None,
+            ast::Macro::MacroDef(mac) => mac.body()?.syntax().text_range().start(),
         };
         Some(InFile::new(id.file_id, def_tt))
     });
diff --git a/crates/hir_expand/src/lib.rs b/crates/hir_expand/src/lib.rs
index b8045fda9..3e332ee47 100644
--- a/crates/hir_expand/src/lib.rs
+++ b/crates/hir_expand/src/lib.rs
@@ -151,7 +151,7 @@ impl HirFileId {
                 let def = loc.def.ast_id().left().and_then(|id| {
                     let def_tt = match id.to_node(db) {
                         ast::Macro::MacroRules(mac) => mac.token_tree()?,
-                        ast::Macro::MacroDef(_) => return None,
+                        ast::Macro::MacroDef(mac) => mac.body()?,
                     };
                     Some(InFile::new(id.file_id, def_tt))
                 });
diff --git a/crates/hir_expand/src/name.rs b/crates/hir_expand/src/name.rs
index 0aeea48d5..a0f8766b0 100644
--- a/crates/hir_expand/src/name.rs
+++ b/crates/hir_expand/src/name.rs
@@ -55,6 +55,15 @@ impl Name {
         }
     }
 
+    /// A fake name for things missing in the source code.
+    ///
+    /// For example, `impl Foo for {}` should be treated as a trait impl for a
+    /// type with a missing name. Similarly, `struct S { : u32 }` should have a
+    /// single field with a missing name.
+    ///
+    /// Ideally, we want a `gensym` semantics for missing names -- each missing
+    /// name is equal only to itself. It's not clear how to implement this in
+    /// salsa though, so we punt on that bit for a moment.
     pub fn missing() -> Name {
         Name::new_text("[missing name]".into())
     }
@@ -75,14 +84,14 @@ impl AsName for ast::NameRef {
     fn as_name(&self) -> Name {
         match self.as_tuple_field() {
             Some(idx) => Name::new_tuple_field(idx),
-            None => Name::resolve(self.text()),
+            None => Name::resolve(&self.text()),
         }
     }
 }
 
 impl AsName for ast::Name {
     fn as_name(&self) -> Name {
-        Name::resolve(self.text())
+        Name::resolve(&self.text())
     }
 }
 
@@ -199,6 +208,8 @@ pub mod known {
         line,
         module_path,
         assert,
+        core_panic,
+        std_panic,
         stringify,
         concat,
         include,
diff --git a/crates/hir_expand/src/quote.rs b/crates/hir_expand/src/quote.rs
index 08bc5aa49..c82487ef0 100644
--- a/crates/hir_expand/src/quote.rs
+++ b/crates/hir_expand/src/quote.rs
@@ -104,6 +104,7 @@ macro_rules! __quote {
     ( . ) => {$crate::__quote!(@PUNCT '.')};
     ( < ) => {$crate::__quote!(@PUNCT '<')};
     ( > ) => {$crate::__quote!(@PUNCT '>')};
+    ( ! ) => {$crate::__quote!(@PUNCT '!')};
 
     ( $first:tt $($tail:tt)+ ) => {
         {