WIP: Actually fix up syntax errors in attribute macro input

crates/hir_def/src/macro_expansion_tests.rs

@@ -345,6 +345,7 @@ fn expand(
         if parse.errors().is_empty() {
             Ok(subtree.clone())
         } else {
+            eprintln!("parse errors: {:?}", parse.errors());
             use tt::{Delimiter, DelimiterKind, Ident, Leaf, Literal, Punct, TokenTree};
             let mut subtree = Subtree::default();
             subtree.token_trees.push(TokenTree::Leaf(

crates/hir_def/src/macro_expansion_tests/proc_macros.rs

@@ -86,6 +86,10 @@ fn attribute_macro_syntax_completion_2() {
         expect![[r##"
 #[proc_macros::identity_when_valid]
 fn foo() { bar.; blub }
-"##]],
+
+fn foo() {
+    bar.;
+    blub
+}"##]],
     );
 }

crates/hir_expand/src/db.rs

@@ -5,8 +5,8 @@
 use base_db::{salsa, SourceDatabase};
 use either::Either;
 use limit::Limit;
-use mbe::{syntax_node_to_token_tree, ExpandError, ExpandResult};
-use rustc_hash::FxHashSet;
+use mbe::{syntax_node_to_token_tree, ExpandError, ExpandResult, SyntheticToken};
+use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::{
     algo::diff,
     ast::{self, HasAttrs, HasDocComments},
@@ -14,7 +14,7 @@
 };
 
 use crate::{
-    ast_id_map::AstIdMap, hygiene::HygieneFrame, BuiltinAttrExpander, BuiltinDeriveExpander,
+    ast_id_map::AstIdMap, fixup, hygiene::HygieneFrame, BuiltinAttrExpander, BuiltinDeriveExpander,
     BuiltinFnLikeExpander, ExpandTo, HirFileId, HirFileIdRepr, MacroCallId, MacroCallKind,
     MacroCallLoc, MacroDefId, MacroDefKind, MacroFile, ProcMacroExpander,
 };
@@ -146,8 +146,10 @@ pub fn expand_speculative(
 
     // Build the subtree and token mapping for the speculative args
     let censor = censor_for_macro_input(&loc, &speculative_args);
+    let mut fixups = fixup::fixup_syntax(&speculative_args);
+    fixups.replace.extend(censor.into_iter().map(|node| (node, Vec::new())));
     let (mut tt, spec_args_tmap) =
-        mbe::syntax_node_to_token_tree_censored(&speculative_args, &censor);
+        mbe::syntax_node_to_token_tree_censored(&speculative_args, fixups.replace, fixups.append);
 
     let (attr_arg, token_id) = match loc.kind {
         MacroCallKind::Attr { invoc_attr_index, .. } => {
@@ -294,8 +296,17 @@ fn macro_arg(db: &dyn AstDatabase, id: MacroCallId) -> Option<Arc<(tt::Subtree,
     let loc = db.lookup_intern_macro_call(id);
 
     let node = SyntaxNode::new_root(arg);
+    eprintln!("input text:\n{node}");
+    eprintln!("input syntax:\n{node:#?}");
     let censor = censor_for_macro_input(&loc, &node);
-    let (mut tt, tmap) = mbe::syntax_node_to_token_tree_censored(&node, &censor);
+    // TODO only fixup for attribute macro input
+    let mut fixups = fixup::fixup_syntax(&node);
+    fixups.replace.extend(censor.into_iter().map(|node| (node, Vec::new())));
+    eprintln!("fixups: {fixups:?}");
+    let (mut tt, tmap) =
+        mbe::syntax_node_to_token_tree_censored(&node, fixups.replace, fixups.append);
+
+    eprintln!("fixed-up input: {}", tt);
 
     if loc.def.is_proc_macro() {
         // proc macros expect their inputs without parentheses, MBEs expect it with them included

crates/hir_expand/src/lib.rs

@@ -15,6 +15,7 @@
 pub mod quote;
 pub mod eager;
 pub mod mod_path;
+mod fixup;
 
 pub use mbe::{ExpandError, ExpandResult, Origin};
 

crates/mbe/src/lib.rs

@@ -30,7 +30,7 @@
 pub use crate::{
     syntax_bridge::{
         parse_exprs_with_sep, parse_to_token_tree, syntax_node_to_token_tree,
-        syntax_node_to_token_tree_censored, token_tree_to_syntax_node,
+        syntax_node_to_token_tree_censored, token_tree_to_syntax_node, SyntheticToken,
     },
     token_map::TokenMap,
 };

crates/mbe/src/syntax_bridge.rs

@@ -15,22 +15,26 @@
 /// Convert the syntax node to a `TokenTree` (what macro
 /// will consume).
 pub fn syntax_node_to_token_tree(node: &SyntaxNode) -> (tt::Subtree, TokenMap) {
-    syntax_node_to_token_tree_censored(node, &Default::default())
+    syntax_node_to_token_tree_censored(node, Default::default(), Default::default())
 }
 
+// TODO rename
 /// Convert the syntax node to a `TokenTree` (what macro will consume)
 /// with the censored range excluded.
 pub fn syntax_node_to_token_tree_censored(
     node: &SyntaxNode,
-    censor: &FxHashSet<SyntaxNode>,
+    replace: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+    append: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
 ) -> (tt::Subtree, TokenMap) {
     let global_offset = node.text_range().start();
-    let mut c = Convertor::new(node, global_offset, censor);
+    let mut c = Convertor::new(node, global_offset, replace, append);
     let subtree = convert_tokens(&mut c);
     c.id_alloc.map.shrink_to_fit();
     (subtree, c.id_alloc.map)
 }
 
+pub type SyntheticToken = (SyntaxKind, SmolStr);
+
 // The following items are what `rustc` macro can be parsed into :
 // link: https://github.com/rust-lang/rust/blob/9ebf47851a357faa4cd97f4b1dc7835f6376e639/src/libsyntax/ext/expand.rs#L141
 // * Expr(P<ast::Expr>)                     -> token_tree_to_expr
@@ -465,86 +469,124 @@ fn id_alloc(&mut self) -> &mut TokenIdAlloc {
     }
 }
 
-struct Convertor<'c> {
+struct Convertor {
     id_alloc: TokenIdAlloc,
     current: Option<SyntaxToken>,
+    current_synthetic: Vec<SyntheticToken>,
     preorder: PreorderWithTokens,
-    censor: &'c FxHashSet<SyntaxNode>,
+    replace: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+    append: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
     range: TextRange,
     punct_offset: Option<(SyntaxToken, TextSize)>,
 }
 
-impl<'c> Convertor<'c> {
+impl Convertor {
     fn new(
         node: &SyntaxNode,
         global_offset: TextSize,
-        censor: &'c FxHashSet<SyntaxNode>,
-    ) -> Convertor<'c> {
+        replace: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+        append: FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+    ) -> Convertor {
         let range = node.text_range();
         let mut preorder = node.preorder_with_tokens();
-        let first = Self::next_token(&mut preorder, censor);
+        let (first, synthetic) = Self::next_token(&mut preorder, &replace, &append);
         Convertor {
             id_alloc: { TokenIdAlloc { map: TokenMap::default(), global_offset, next_id: 0 } },
             current: first,
+            current_synthetic: synthetic,
             preorder,
             range,
-            censor,
+            replace,
+            append,
             punct_offset: None,
         }
     }
 
     fn next_token(
         preorder: &mut PreorderWithTokens,
-        censor: &FxHashSet<SyntaxNode>,
-    ) -> Option<SyntaxToken> {
+        replace: &FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+        append: &FxHashMap<SyntaxNode, Vec<SyntheticToken>>,
+    ) -> (Option<SyntaxToken>, Vec<SyntheticToken>) {
         while let Some(ev) = preorder.next() {
             let ele = match ev {
                 WalkEvent::Enter(ele) => ele,
+                WalkEvent::Leave(SyntaxElement::Node(node)) => {
+                    if let Some(v) = append.get(&node) {
+                        eprintln!("after {:?}, appending {:?}", node, v);
+                        if !v.is_empty() {
+                            let mut reversed = v.clone();
+                            reversed.reverse();
+                            return (None, reversed);
+                        }
+                    }
+                    continue;
+                }
                 _ => continue,
             };
             match ele {
-                SyntaxElement::Token(t) => return Some(t),
-                SyntaxElement::Node(node) if censor.contains(&node) => preorder.skip_subtree(),
-                SyntaxElement::Node(_) => (),
+                SyntaxElement::Token(t) => return (Some(t), Vec::new()),
+                SyntaxElement::Node(node) => {
+                    if let Some(v) = replace.get(&node) {
+                        preorder.skip_subtree();
+                        eprintln!("replacing {:?} by {:?}", node, v);
+                        if !v.is_empty() {
+                            let mut reversed = v.clone();
+                            reversed.reverse();
+                            return (None, reversed);
+                        }
+                    }
+                }
             }
         }
-        None
+        (None, Vec::new())
     }
 }
 
 #[derive(Debug)]
 enum SynToken {
     Ordinary(SyntaxToken),
+    // FIXME is this supposed to be `Punct`?
     Punch(SyntaxToken, TextSize),
+    Synthetic(SyntheticToken),
 }
 
 impl SynToken {
-    fn token(&self) -> &SyntaxToken {
+    fn token(&self) -> Option<&SyntaxToken> {
         match self {
-            SynToken::Ordinary(it) | SynToken::Punch(it, _) => it,
+            SynToken::Ordinary(it) | SynToken::Punch(it, _) => Some(it),
+            SynToken::Synthetic(_) => None,
         }
     }
 }
 
-impl<'a> SrcToken<Convertor<'a>> for SynToken {
-    fn kind(&self, _ctx: &Convertor<'a>) -> SyntaxKind {
-        self.token().kind()
+impl SrcToken<Convertor> for SynToken {
+    fn kind(&self, _ctx: &Convertor) -> SyntaxKind {
+        match self {
+            SynToken::Ordinary(token) => token.kind(),
+            SynToken::Punch(token, _) => token.kind(),
+            SynToken::Synthetic((kind, _)) => *kind,
+        }
     }
-    fn to_char(&self, _ctx: &Convertor<'a>) -> Option<char> {
+    fn to_char(&self, _ctx: &Convertor) -> Option<char> {
         match self {
             SynToken::Ordinary(_) => None,
             SynToken::Punch(it, i) => it.text().chars().nth((*i).into()),
+            SynToken::Synthetic(_) => None,
         }
     }
-    fn to_text(&self, _ctx: &Convertor<'a>) -> SmolStr {
-        self.token().text().into()
+    fn to_text(&self, _ctx: &Convertor) -> SmolStr {
+        match self {
+            SynToken::Ordinary(token) => token.text().into(),
+            SynToken::Punch(token, _) => token.text().into(),
+            SynToken::Synthetic((_, text)) => text.clone(),
+        }
     }
 }
 
-impl TokenConvertor for Convertor<'_> {
+impl TokenConvertor for Convertor {
     type Token = SynToken;
     fn convert_doc_comment(&self, token: &Self::Token) -> Option<Vec<tt::TokenTree>> {
-        convert_doc_comment(token.token())
+        convert_doc_comment(token.token()?)
     }
 
     fn bump(&mut self) -> Option<(Self::Token, TextRange)> {
@@ -558,11 +600,25 @@ fn bump(&mut self) -> Option<(Self::Token, TextRange)> {
             }
         }
 
+        if let Some(synth_token) = self.current_synthetic.pop() {
+            if self.current_synthetic.is_empty() {
+                let (new_current, new_synth) =
+                    Self::next_token(&mut self.preorder, &self.replace, &self.append);
+                self.current = new_current;
+                self.current_synthetic = new_synth;
+            }
+            // TODO fix range?
+            return Some((SynToken::Synthetic(synth_token), self.range));
+        }
+
         let curr = self.current.clone()?;
         if !&self.range.contains_range(curr.text_range()) {
             return None;
         }
-        self.current = Self::next_token(&mut self.preorder, self.censor);
+        let (new_current, new_synth) =
+            Self::next_token(&mut self.preorder, &self.replace, &self.append);
+        self.current = new_current;
+        self.current_synthetic = new_synth;
         let token = if curr.kind().is_punct() {
             self.punct_offset = Some((curr.clone(), 0.into()));
             let range = curr.text_range();
@@ -585,6 +641,11 @@ fn peek(&self) -> Option<Self::Token> {
             }
         }
 
+        if let Some(synth_token) = self.current_synthetic.last() {
+            // TODO fix range?
+            return Some(SynToken::Synthetic(synth_token.clone()));
+        }
+
         let curr = self.current.clone()?;
         if !self.range.contains_range(curr.text_range()) {
             return None;