7 files changed, 202 insertions, 24 deletions

diff --git a/crates/ra_mbe/Cargo.toml b/crates/ra_mbe/Cargo.toml
index 1e5ed6907..68f559295 100644
--- a/crates/ra_mbe/Cargo.toml
+++ b/crates/ra_mbe/Cargo.toml
@@ -11,3 +11,4 @@ tt = { path = "../ra_tt", package = "ra_tt" }
 itertools = "0.8.0"
 rustc-hash = "1.0.0"
 smallvec = "0.6.9"
+log = "0.4.5"
diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index 7ebba807c..7817232d6 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -437,6 +437,30 @@ impl_froms!(TokenTree: Leaf, Subtree);
     }
 
     #[test]
+    fn test_match_group_zero_match() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {            
+            ( $($i:ident)* ) => ();            
+        }"#,
+        );
+
+        assert_expansion(&rules, "foo! ()", "");
+    }
+
+    #[test]
+    fn test_match_group_in_group() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {            
+            { $( ( $($i:ident)* ) )* } => ( $( ( $($i)* ) )* );
+        }"#,
+        );
+
+        assert_expansion(&rules, "foo! ( (a b) )", "(a b)");
+    }
+
+    #[test]
     fn test_expand_to_item_list() {
         let rules = create_rules(
             "
@@ -1118,7 +1142,37 @@ macro_rules! impl_fn_for_zst  {
             |$( $arg: ident: $ArgTy: ty ),*| -> $ReturnTy: ty
 $body: block; )+
         } => {
-            fn foo(){}
+           $(
+            $( #[$attr] )*
+            struct $Name;
+
+            impl $( <$( $lifetime ),+> )? Fn<($( $ArgTy, )*)> for $Name {
+                #[inline]
+                extern "rust-call" fn call(&self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
+                    $body
+                }
+            }
+
+            impl $( <$( $lifetime ),+> )? FnMut<($( $ArgTy, )*)> for $Name {
+                #[inline]
+                extern "rust-call" fn call_mut(
+                    &mut self,
+                    ($( $arg, )*): ($( $ArgTy, )*)
+                ) -> $ReturnTy {
+                    Fn::call(&*self, ($( $arg, )*))
+                }
+            }
+
+            impl $( <$( $lifetime ),+> )? FnOnce<($( $ArgTy, )*)> for $Name {
+                type Output = $ReturnTy;
+
+                #[inline]
+                extern "rust-call" fn call_once(self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
+                    Fn::call(&self, ($( $arg, )*))
+                }
+            }
+        )+
+}
         }
 }
 "#,
@@ -1141,7 +1195,7 @@ impl_fn_for_zst !   {
      } ; 
  }
 "#, 
-        "fn foo () {}");
+        "# [derive (Clone)] struct CharEscapeDebugContinue ; impl  Fn < (char ,) > for CharEscapeDebugContinue {# [inline] extern \"rust-call\" fn call (& self , (c ,) : (char ,)) -> char :: EscapeDebug {{c . escape_debug_ext (false)}}} impl  FnMut < (char ,) > for CharEscapeDebugContinue {# [inline] extern \"rust-call\" fn call_mut (& mut self , (c ,) : (char ,)) -> char :: EscapeDebug {Fn :: call (&* self , (c ,))}} impl  FnOnce < (char ,) > for CharEscapeDebugContinue {type Output = char :: EscapeDebug ; # [inline] extern \"rust-call\" fn call_once (self , (c ,) : (char ,)) -> char :: EscapeDebug {Fn :: call (& self , (c ,))}} # [derive (Clone)] struct CharEscapeUnicode ; impl  Fn < (char ,) > for CharEscapeUnicode {# [inline] extern \"rust-call\" fn call (& self , (c ,) : (char ,)) -> char :: EscapeUnicode {{c . escape_unicode ()}}} impl  FnMut < (char ,) > for CharEscapeUnicode {# [inline] extern \"rust-call\" fn call_mut (& mut self , (c ,) : (char ,)) -> char :: EscapeUnicode {Fn :: call (&* self , (c ,))}} impl  FnOnce < (char ,) > for CharEscapeUnicode {type Output = char :: EscapeUnicode ; # [inline] extern \"rust-call\" fn call_once (self , (c ,) : (char ,)) -> char :: EscapeUnicode {Fn :: call (& self , (c ,))}} # [derive (Clone)] struct CharEscapeDefault ; impl  Fn < (char ,) > for CharEscapeDefault {# [inline] extern \"rust-call\" fn call (& self , (c ,) : (char ,)) -> char :: EscapeDefault {{c . escape_default ()}}} impl  FnMut < (char ,) > for CharEscapeDefault {# [inline] extern \"rust-call\" fn call_mut (& mut self , (c ,) : (char ,)) -> char :: EscapeDefault {Fn :: call (&* self , (c ,))}} impl  FnOnce < (char ,) > for CharEscapeDefault {type Output = char :: EscapeDefault ; # [inline] extern \"rust-call\" fn call_once (self , (c ,) : (char ,)) -> char :: EscapeDefault {Fn :: call (& self , (c ,))}}");
     }
 
     #[test]
@@ -1160,4 +1214,58 @@ impl_fn_for_zst !   {
         assert_expansion(&rules, r#"impl_nonzero_fmt ! { # [ stable ( feature = "nonzero" , since = "1.28.0" ) ] ( Debug , Display , Binary , Octal , LowerHex , UpperHex ) for NonZeroU8 }"#, 
         "fn foo () {}");
     }
+
+    #[test]
+    fn test_cfg_if_items() {
+        // from https://github.com/rust-lang/rust/blob/33fe1131cadba69d317156847be9a402b89f11bb/src/libstd/macros.rs#L986
+        let rules = create_rules(
+            r#"
+        macro_rules! __cfg_if_items {
+            (($($not:meta,)*) ; ) => {};
+            (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
+                 __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
+            }
+        }
+"#,
+        );
+
+        assert_expansion(&rules, r#"__cfg_if_items ! { ( rustdoc , ) ; ( ( ) ( # [ cfg ( any ( target_os = "redox" , unix ) ) ] # [ stable ( feature = "rust1" , since = "1.0.0" ) ] pub use sys :: ext as unix ; # [ cfg ( windows ) ] # [ stable ( feature = "rust1" , since = "1.0.0" ) ] pub use sys :: ext as windows ; # [ cfg ( any ( target_os = "linux" , target_os = "l4re" ) ) ] pub mod linux ; ) ) , }"#,         
+        "__cfg_if_items ! {(rustdoc , ) ; }");
+    }
+
+    #[test]
+    fn test_cfg_if_main() {
+        // from https://github.com/rust-lang/rust/blob/3d211248393686e0f73851fc7548f6605220fbe1/src/libpanic_unwind/macros.rs#L9
+        let rules = create_rules(
+            r#"
+        macro_rules! cfg_if {
+            ($(
+                if #[cfg($($meta:meta),*)] { $($it:item)* }
+            ) else * else {
+                $($it2:item)*
+            }) => {
+                __cfg_if_items! {
+                    () ;
+                    $( ( ($($meta),*) ($($it)*) ), )*
+                    ( () ($($it2)*) ),
+                }
+            }
+        }
+"#,
+        );
+
+        assert_expansion(&rules, r#"
+cfg_if !   { 
+     if   # [ cfg ( target_env   =   "msvc" ) ]   { 
+         // no extra unwinder support needed 
+     }   else   if   # [ cfg ( all ( target_arch   =   "wasm32" ,   not ( target_os   =   "emscripten" ) ) ) ]   { 
+         // no unwinder on the system! 
+     }   else   { 
+         mod   libunwind ; 
+         pub   use   libunwind :: * ; 
+     } 
+ }        
+"#,         
+        "__cfg_if_items ! {() ;  (() (mod libunwind ; pub use libunwind :: * ;)) ,}");
+    }
 }
diff --git a/crates/ra_mbe/src/mbe_expander.rs b/crates/ra_mbe/src/mbe_expander.rs
index 7411dd8b1..d5189b537 100644
--- a/crates/ra_mbe/src/mbe_expander.rs
+++ b/crates/ra_mbe/src/mbe_expander.rs
@@ -21,7 +21,10 @@ fn expand_rule(rule: &crate::Rule, input: &tt::Subtree) -> Result<tt::Subtree, E
     if !input.is_eof() {
         return Err(ExpandError::UnexpectedToken);
     }
-    expand_subtree(&rule.rhs, &bindings, &mut Vec::new())
+
+    let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new(), var_expanded: false };
+
+    expand_subtree(&rule.rhs, &mut ctx)
 }
 
 /// The actual algorithm for expansion is not too hard, but is pretty tricky.
@@ -225,7 +228,7 @@ fn match_lhs(pattern: &crate::Subtree, input: &mut TtCursor) -> Result<Bindings,
             crate::TokenTree::Repeat(crate::Repeat { subtree, kind, separator }) => {
                 // Dirty hack to make macro-expansion terminate.
                 // This should be replaced by a propper macro-by-example implementation
-                let mut limit = 128;
+                let mut limit = 65536;
                 let mut counter = 0;
 
                 let mut memento = input.save();
@@ -236,6 +239,7 @@ fn match_lhs(pattern: &crate::Subtree, input: &mut TtCursor) -> Result<Bindings,
                             counter += 1;
                             limit -= 1;
                             if limit == 0 {
+                                log::warn!("match_lhs excced in repeat pattern exceed limit => {:#?}\n{:#?}\n{:#?}\n{:#?}", subtree, input, kind, separator);
                                 break;
                             }
 
@@ -303,15 +307,21 @@ fn match_lhs(pattern: &crate::Subtree, input: &mut TtCursor) -> Result<Bindings,
     Ok(res)
 }
 
+#[derive(Debug)]
+struct ExpandCtx<'a> {
+    bindings: &'a Bindings,
+    nesting: Vec<usize>,
+    var_expanded: bool,
+}
+
 fn expand_subtree(
     template: &crate::Subtree,
-    bindings: &Bindings,
-    nesting: &mut Vec<usize>,
+    ctx: &mut ExpandCtx,
 ) -> Result<tt::Subtree, ExpandError> {
     let token_trees = template
         .token_trees
         .iter()
-        .map(|it| expand_tt(it, bindings, nesting))
+        .map(|it| expand_tt(it, ctx))
         .collect::<Result<Vec<_>, ExpandError>>()?;
 
     Ok(tt::Subtree { token_trees, delimiter: template.delimiter })
@@ -333,26 +343,43 @@ fn reduce_single_token(mut subtree: tt::Subtree) -> tt::TokenTree {
 
 fn expand_tt(
     template: &crate::TokenTree,
-    bindings: &Bindings,
-    nesting: &mut Vec<usize>,
+    ctx: &mut ExpandCtx,
 ) -> Result<tt::TokenTree, ExpandError> {
     let res: tt::TokenTree = match template {
-        crate::TokenTree::Subtree(subtree) => expand_subtree(subtree, bindings, nesting)?.into(),
+        crate::TokenTree::Subtree(subtree) => expand_subtree(subtree, ctx)?.into(),
         crate::TokenTree::Repeat(repeat) => {
             let mut token_trees: Vec<tt::TokenTree> = Vec::new();
-            nesting.push(0);
+            ctx.nesting.push(0);
             // Dirty hack to make macro-expansion terminate.
             // This should be replaced by a propper macro-by-example implementation
-            let mut limit = 128;
+            let mut limit = 65536;
             let mut has_seps = 0;
+            let mut counter = 0;
+
+            let mut some_var_expanded = false;
+            ctx.var_expanded = false;
+
+            while let Ok(t) = expand_subtree(&repeat.subtree, ctx) {
+                // if no var expaned in the child, we count it as a fail
+                if !ctx.var_expanded {
+                    break;
+                }
+                some_var_expanded = true;
+                ctx.var_expanded = false;
 
-            while let Ok(t) = expand_subtree(&repeat.subtree, bindings, nesting) {
+                counter += 1;
                 limit -= 1;
                 if limit == 0 {
+                    log::warn!(
+                        "expand_tt excced in repeat pattern exceed limit => {:#?}\n{:#?}",
+                        template,
+                        ctx
+                    );
                     break;
                 }
-                let idx = nesting.pop().unwrap();
-                nesting.push(idx + 1);
+
+                let idx = ctx.nesting.pop().unwrap();
+                ctx.nesting.push(idx + 1);
                 token_trees.push(reduce_single_token(t).into());
 
                 if let Some(ref sep) = repeat.separator {
@@ -374,12 +401,23 @@ fn expand_tt(
                         }
                     }
                 }
+
+                if let crate::RepeatKind::ZeroOrOne = repeat.kind {
+                    break;
+                }
             }
-            nesting.pop().unwrap();
+
+            ctx.var_expanded = some_var_expanded;
+
+            ctx.nesting.pop().unwrap();
             for _ in 0..has_seps {
                 token_trees.pop();
             }
 
+            if crate::RepeatKind::OneOrMore == repeat.kind && counter == 0 {
+                return Err(ExpandError::UnexpectedToken);
+            }
+
             // Check if it is a singel token subtree without any delimiter
             // e.g {Delimiter:None> ['>'] /Delimiter:None>}
             reduce_single_token(tt::Subtree { token_trees, delimiter: tt::Delimiter::None })
@@ -396,7 +434,8 @@ fn expand_tt(
                     tt::Leaf::from(tt::Ident { text: "$crate".into(), id: TokenId::unspecified() })
                         .into()
                 } else {
-                    let tkn = bindings.get(&v.text, nesting)?.clone();
+                    let tkn = ctx.bindings.get(&v.text, &ctx.nesting)?.clone();
+                    ctx.var_expanded = true;
 
                     if let tt::TokenTree::Subtree(subtree) = tkn {
                         reduce_single_token(subtree)
diff --git a/crates/ra_mbe/src/subtree_source.rs b/crates/ra_mbe/src/subtree_source.rs
index e979777fe..845020f4e 100644
--- a/crates/ra_mbe/src/subtree_source.rs
+++ b/crates/ra_mbe/src/subtree_source.rs
@@ -212,7 +212,7 @@ impl<'a> SubTreeWalker<'a> {
 }
 
 pub(crate) trait Querier {
-    fn token(&self, uidx: usize) -> (SyntaxKind, SmolStr);
+    fn token(&self, uidx: usize) -> (SyntaxKind, SmolStr, bool);
 }
 
 // A wrapper class for ref cell
@@ -292,9 +292,10 @@ impl<'a> WalkerOwner<'a> {
 }
 
 impl<'a> Querier for WalkerOwner<'a> {
-    fn token(&self, uidx: usize) -> (SyntaxKind, SmolStr) {
-        let tkn = self.get(uidx).unwrap();
-        (tkn.kind, tkn.text)
+    fn token(&self, uidx: usize) -> (SyntaxKind, SmolStr, bool) {
+        self.get(uidx)
+            .map(|tkn| (tkn.kind, tkn.text, tkn.is_joint_to_next))
+            .unwrap_or_else(|| (SyntaxKind::EOF, "".into(), false))
     }
 }
 
diff --git a/crates/ra_mbe/src/syntax_bridge.rs b/crates/ra_mbe/src/syntax_bridge.rs
index 9cca19dbb..e0f228ce9 100644
--- a/crates/ra_mbe/src/syntax_bridge.rs
+++ b/crates/ra_mbe/src/syntax_bridge.rs
@@ -123,6 +123,11 @@ fn convert_tt(
     global_offset: TextUnit,
     tt: &SyntaxNode,
 ) -> Option<tt::Subtree> {
+    // This tree is empty
+    if tt.first_child_or_token().is_none() {
+        return Some(tt::Subtree { token_trees: vec![], delimiter: tt::Delimiter::None });
+    }
+
     let first_child = tt.first_child_or_token()?;
     let last_child = tt.last_child_or_token()?;
     let (delimiter, skip_first) = match (first_child.kind(), last_child.kind()) {
@@ -233,7 +238,16 @@ impl<'a, Q: Querier> TreeSink for TtTreeSink<'a, Q> {
         self.text_pos += TextUnit::of_str(&self.buf);
         let text = SmolStr::new(self.buf.as_str());
         self.buf.clear();
-        self.inner.token(kind, text)
+        self.inner.token(kind, text);
+
+        // // Add a white space to token
+        // let (last_kind, _, last_joint_to_next ) = self.src_querier.token(self.token_pos-n_tokens as usize);
+        // if !last_joint_to_next && last_kind.is_punct() {
+        //     let (cur_kind, _, _ ) = self.src_querier.token(self.token_pos);
+        //     if cur_kind.is_punct() {
+        //         self.inner.token(WHITESPACE, " ".into());
+        //     }
+        // }
     }
 
     fn start_node(&mut self, kind: SyntaxKind) {
diff --git a/crates/ra_mbe/src/tt_cursor.rs b/crates/ra_mbe/src/tt_cursor.rs
index 343416421..eef642a9c 100644
--- a/crates/ra_mbe/src/tt_cursor.rs
+++ b/crates/ra_mbe/src/tt_cursor.rs
@@ -3,7 +3,7 @@ use crate::subtree_parser::Parser;
 use crate::subtree_source::TokenPeek;
 use smallvec::{SmallVec, smallvec};
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub(crate) struct TtCursor<'a> {
     subtree: &'a tt::Subtree,
     pos: usize,
diff --git a/crates/ra_parser/src/grammar.rs b/crates/ra_parser/src/grammar.rs
index 67eae749d..a538ec081 100644
--- a/crates/ra_parser/src/grammar.rs
+++ b/crates/ra_parser/src/grammar.rs
@@ -119,7 +119,22 @@ pub(crate) fn meta_item(p: &mut Parser) {
             items::token_tree(p);
             break;
         } else {
-            p.bump();
+            // https://doc.rust-lang.org/reference/attributes.html
+            // https://doc.rust-lang.org/reference/paths.html#simple-paths
+            // The start of an meta must be a simple path
+            match p.current() {
+                IDENT | COLONCOLON | SUPER_KW | SELF_KW | CRATE_KW => p.bump(),
+                EQ => {
+                    p.bump();
+                    match p.current() {
+                        c if c.is_literal() => p.bump(),
+                        TRUE_KW | FALSE_KW => p.bump(),
+                        _ => {}
+                    }
+                    break;
+                }
+                _ => break,
+            }
         }
     }