use usual token tree for macro expansion

1 files changed, 146 insertions, 142 deletions

diff --git a/crates/ra_mbe/src/mbe_expander/transcriber.rs b/crates/ra_mbe/src/mbe_expander/transcriber.rs
index a3df1b7de..c22680b93 100644
--- a/crates/ra_mbe/src/mbe_expander/transcriber.rs
+++ b/crates/ra_mbe/src/mbe_expander/transcriber.rs
@@ -1,16 +1,20 @@
+//! Transcraber takes a template, like `fn $ident() {}`, a set of bindings like
+//! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
+
 use ra_syntax::SmolStr;
 
 use crate::{
     mbe_expander::{Binding, Bindings, Fragment},
+    parser::{parse_template, Op, RepeatKind, Separator},
     ExpandError,
 };
 
 impl Bindings {
-    fn contains(&self, name: &SmolStr) -> bool {
+    fn contains(&self, name: &str) -> bool {
         self.inner.contains_key(name)
     }
 
-    fn get(&self, name: &SmolStr, nesting: &[usize]) -> Result<&Fragment, ExpandError> {
+    fn get(&self, name: &str, nesting: &[usize]) -> Result<&Fragment, ExpandError> {
         let mut b = self.inner.get(name).ok_or_else(|| {
             ExpandError::BindingError(format!("could not find binding `{}`", name))
         })?;
@@ -43,11 +47,12 @@ impl Bindings {
 }
 
 pub(super) fn transcribe(
+    template: &tt::Subtree,
     bindings: &Bindings,
-    template: &crate::Subtree,
 ) -> Result<tt::Subtree, ExpandError> {
+    assert!(template.delimiter == tt::Delimiter::None);
     let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new(), var_expanded: false };
-    expand_subtree(template, &mut ctx)
+    expand_subtree(&mut ctx, template)
 }
 
 #[derive(Debug)]
@@ -57,159 +62,158 @@ struct ExpandCtx<'a> {
     var_expanded: bool,
 }
 
-fn expand_subtree(
-    template: &crate::Subtree,
-    ctx: &mut ExpandCtx,
-) -> Result<tt::Subtree, ExpandError> {
+fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> Result<tt::Subtree, ExpandError> {
     let mut buf: Vec<tt::TokenTree> = Vec::new();
-    for tt in template.token_trees.iter() {
-        let tt = expand_tt(tt, ctx)?;
-        push_fragment(&mut buf, tt);
+    for op in parse_template(template) {
+        match op? {
+            Op::TokenTree(tt @ tt::TokenTree::Leaf(..)) => buf.push(tt.clone()),
+            Op::TokenTree(tt::TokenTree::Subtree(tt)) => {
+                let tt = expand_subtree(ctx, tt)?;
+                buf.push(tt.into());
+            }
+            Op::Var { name, kind: _ } => {
+                let fragment = expand_var(ctx, name)?;
+                push_fragment(&mut buf, fragment);
+            }
+            Op::Repeat { subtree, kind, separator } => {
+                let fragment = expand_repeat(ctx, subtree, kind, separator)?;
+                push_fragment(&mut buf, fragment)
+            }
+        }
     }
-
     Ok(tt::Subtree { delimiter: template.delimiter, token_trees: buf })
 }
 
-fn expand_tt(template: &crate::TokenTree, ctx: &mut ExpandCtx) -> Result<Fragment, ExpandError> {
-    let res: tt::TokenTree = match template {
-        crate::TokenTree::Subtree(subtree) => expand_subtree(subtree, ctx)?.into(),
-        crate::TokenTree::Repeat(repeat) => {
-            let mut buf: Vec<tt::TokenTree> = Vec::new();
-            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 = 65536;
-            let mut has_seps = 0;
-            let mut counter = 0;
-
-            // We store the old var expanded value, and restore it later
-            // It is because before this `$repeat`,
-            // it is possible some variables already expanad in the same subtree
-            //
-            // `some_var_expanded` keep check if the deeper subtree has expanded variables
-            let mut some_var_expanded = false;
-            let old_var_expanded = ctx.var_expanded;
-            ctx.var_expanded = false;
-
-            while let Ok(t) = expand_subtree(&repeat.subtree, ctx) {
-                // if no var expanded in the child, we count it as a fail
-                if !ctx.var_expanded {
-                    break;
-                }
+fn expand_var(ctx: &mut ExpandCtx, v: &SmolStr) -> Result<Fragment, ExpandError> {
+    let res = if v == "crate" {
+        // FIXME: Properly handle $crate token
+        let tt =
+            tt::Leaf::from(tt::Ident { text: "$crate".into(), id: tt::TokenId::unspecified() })
+                .into();
+        Fragment::Tokens(tt)
+    } else if !ctx.bindings.contains(v) {
+        // Note that it is possible to have a `$var` inside a macro which is not bound.
+        // For example:
+        // ```
+        // macro_rules! foo {
+        //     ($a:ident, $b:ident, $c:tt) => {
+        //         macro_rules! bar {
+        //             ($bi:ident) => {
+        //                 fn $bi() -> u8 {$c}
+        //             }
+        //         }
+        //     }
+        // ```
+        // We just treat it a normal tokens
+        let tt = tt::Subtree {
+            delimiter: tt::Delimiter::None,
+            token_trees: vec![
+                tt::Leaf::from(tt::Punct { char: '$', spacing: tt::Spacing::Alone }).into(),
+                tt::Leaf::from(tt::Ident { text: v.clone(), id: tt::TokenId::unspecified() })
+                    .into(),
+            ],
+        }
+        .into();
+        Fragment::Tokens(tt)
+    } else {
+        let fragment = ctx.bindings.get(&v, &ctx.nesting)?.clone();
+        ctx.var_expanded = true;
+        fragment
+    };
+    Ok(res)
+}
 
-                // Reset `ctx.var_expandeded` to see if there is other expanded variable
-                // in the next matching
-                some_var_expanded = true;
-                ctx.var_expanded = false;
-
-                counter += 1;
-                limit -= 1;
-                if limit == 0 {
-                    log::warn!(
-                        "expand_tt excced in repeat pattern exceed limit => {:#?}\n{:#?}",
-                        template,
-                        ctx
-                    );
-                    break;
-                }
+fn expand_repeat(
+    ctx: &mut ExpandCtx,
+    template: &tt::Subtree,
+    kind: RepeatKind,
+    separator: Option<Separator>,
+) -> Result<Fragment, ExpandError> {
+    let mut buf: Vec<tt::TokenTree> = Vec::new();
+    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 = 65536;
+    let mut has_seps = 0;
+    let mut counter = 0;
+
+    // We store the old var expanded value, and restore it later
+    // It is because before this `$repeat`,
+    // it is possible some variables already expanad in the same subtree
+    //
+    // `some_var_expanded` keep check if the deeper subtree has expanded variables
+    let mut some_var_expanded = false;
+    let old_var_expanded = ctx.var_expanded;
+    ctx.var_expanded = false;
+
+    while let Ok(mut t) = expand_subtree(ctx, template) {
+        t.delimiter = tt::Delimiter::None;
+        // if no var expanded in the child, we count it as a fail
+        if !ctx.var_expanded {
+            break;
+        }
 
-                let idx = ctx.nesting.pop().unwrap();
-                ctx.nesting.push(idx + 1);
-                push_subtree(&mut buf, t);
-
-                if let Some(ref sep) = repeat.separator {
-                    match sep {
-                        crate::Separator::Ident(ident) => {
-                            has_seps = 1;
-                            buf.push(tt::Leaf::from(ident.clone()).into());
-                        }
-                        crate::Separator::Literal(lit) => {
-                            has_seps = 1;
-                            buf.push(tt::Leaf::from(lit.clone()).into());
-                        }
-
-                        crate::Separator::Puncts(puncts) => {
-                            has_seps = puncts.len();
-                            for punct in puncts {
-                                buf.push(tt::Leaf::from(*punct).into());
-                            }
-                        }
-                    }
+        // Reset `ctx.var_expandeded` to see if there is other expanded variable
+        // in the next matching
+        some_var_expanded = true;
+        ctx.var_expanded = false;
+
+        counter += 1;
+        limit -= 1;
+        if limit == 0 {
+            log::warn!(
+                "expand_tt excced in repeat pattern exceed limit => {:#?}\n{:#?}",
+                template,
+                ctx
+            );
+            break;
+        }
+
+        let idx = ctx.nesting.pop().unwrap();
+        ctx.nesting.push(idx + 1);
+        push_subtree(&mut buf, t);
+
+        if let Some(ref sep) = separator {
+            match sep {
+                Separator::Ident(ident) => {
+                    has_seps = 1;
+                    buf.push(tt::Leaf::from(ident.clone()).into());
+                }
+                Separator::Literal(lit) => {
+                    has_seps = 1;
+                    buf.push(tt::Leaf::from(lit.clone()).into());
                 }
 
-                if let crate::RepeatKind::ZeroOrOne = repeat.kind {
-                    break;
+                Separator::Puncts(puncts) => {
+                    has_seps = puncts.len();
+                    for punct in puncts {
+                        buf.push(tt::Leaf::from(*punct).into());
+                    }
                 }
             }
+        }
 
-            // Restore the `var_expanded` by combining old one and the new one
-            ctx.var_expanded = some_var_expanded || old_var_expanded;
+        if RepeatKind::ZeroOrOne == kind {
+            break;
+        }
+    }
 
-            ctx.nesting.pop().unwrap();
-            for _ in 0..has_seps {
-                buf.pop();
-            }
+    // Restore the `var_expanded` by combining old one and the new one
+    ctx.var_expanded = some_var_expanded || old_var_expanded;
 
-            if crate::RepeatKind::OneOrMore == repeat.kind && counter == 0 {
-                return Err(ExpandError::UnexpectedToken);
-            }
+    ctx.nesting.pop().unwrap();
+    for _ in 0..has_seps {
+        buf.pop();
+    }
 
-            // Check if it is a single token subtree without any delimiter
-            // e.g {Delimiter:None> ['>'] /Delimiter:None>}
-            tt::Subtree { delimiter: tt::Delimiter::None, token_trees: buf }.into()
-        }
-        crate::TokenTree::Leaf(leaf) => match leaf {
-            crate::Leaf::Ident(ident) => tt::Leaf::from(tt::Ident {
-                text: ident.text.clone(),
-                id: tt::TokenId::unspecified(),
-            })
-            .into(),
-            crate::Leaf::Punct(punct) => tt::Leaf::from(*punct).into(),
-            crate::Leaf::Var(v) => {
-                if v.text == "crate" {
-                    // FIXME: Properly handle $crate token
-                    tt::Leaf::from(tt::Ident {
-                        text: "$crate".into(),
-                        id: tt::TokenId::unspecified(),
-                    })
-                    .into()
-                } else if !ctx.bindings.contains(&v.text) {
-                    // Note that it is possible to have a `$var` inside a macro which is not bound.
-                    // For example:
-                    // ```
-                    // macro_rules! foo {
-                    //     ($a:ident, $b:ident, $c:tt) => {
-                    //         macro_rules! bar {
-                    //             ($bi:ident) => {
-                    //                 fn $bi() -> u8 {$c}
-                    //             }
-                    //         }
-                    //     }
-                    // ```
-                    // We just treat it a normal tokens
-                    tt::Subtree {
-                        delimiter: tt::Delimiter::None,
-                        token_trees: vec![
-                            tt::Leaf::from(tt::Punct { char: '$', spacing: tt::Spacing::Alone })
-                                .into(),
-                            tt::Leaf::from(tt::Ident {
-                                text: v.text.clone(),
-                                id: tt::TokenId::unspecified(),
-                            })
-                            .into(),
-                        ],
-                    }
-                    .into()
-                } else {
-                    let fragment = ctx.bindings.get(&v.text, &ctx.nesting)?.clone();
-                    ctx.var_expanded = true;
-                    return Ok(fragment);
-                }
-            }
-            crate::Leaf::Literal(l) => tt::Leaf::from(tt::Literal { text: l.text.clone() }).into(),
-        },
-    };
-    Ok(Fragment::Tokens(res))
+    if RepeatKind::OneOrMore == kind && counter == 0 {
+        return Err(ExpandError::UnexpectedToken);
+    }
+
+    // Check if it is a single token subtree without any delimiter
+    // e.g {Delimiter:None> ['>'] /Delimiter:None>}
+    let tt = tt::Subtree { delimiter: tt::Delimiter::None, token_trees: buf }.into();
+    Ok(Fragment::Tokens(tt))
 }
 
 fn push_fragment(buf: &mut Vec<tt::TokenTree>, fragment: Fragment) {