4 files changed, 38 insertions, 9 deletions

diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 86c2fd24..6b1f3d08 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -4,6 +4,14 @@
 #[macro_use]
 mod test;
 
+/// Basic types used around the syntax side.
+pub mod prelude {
+    pub use super::expr::*;
+    pub use super::tree::{SyntaxTree, SyntaxNode, DynamicNode};
+    pub use super::span::{SpanVec, Span, Spanned};
+    pub use super::value::*;
+}
+
 pub mod decoration;
 pub mod expr;
 pub mod tree;
diff --git a/src/syntax/parsing.rs b/src/syntax/parsing.rs
index 7594c14d..bcbcb8d4 100644
--- a/src/syntax/parsing.rs
+++ b/src/syntax/parsing.rs
@@ -13,6 +13,27 @@ use super::tree::{SyntaxTree, SyntaxNode, DynamicNode};
 /// A function which parses a function call into a tree.
 pub type CallParser = dyn Fn(FuncCall, &ParseState) -> Pass<Box<dyn DynamicNode>>;
 
+/// Parse a function call.
+pub trait ParseCall {
+    /// A metadata type whose value is passed into the function parser. This
+    /// allows a single function to do different things depending on the value
+    /// that needs to be given when inserting the function into a
+    /// [scope](crate::syntax::Scope).
+    ///
+    /// For example, the functions `word.spacing`, `line.spacing` and
+    /// `par.spacing` are actually all the same function
+    /// [`ContentSpacingFunc`](crate::library::ContentSpacingFunc) with the
+    /// metadata specifiy which content should be spaced.
+    type Meta: Clone;
+
+    /// Parse the header and body into this function given a context.
+    fn parse(
+        header: FuncCall,
+        state: &ParseState,
+        metadata: Self::Meta,
+    ) -> Pass<Self> where Self: Sized;
+}
+
 /// An invocation of a function.
 #[derive(Debug, Clone, PartialEq)]
 pub struct FuncCall<'s> {
diff --git a/src/syntax/scope.rs b/src/syntax/scope.rs
index d3092944..8fdad6a0 100644
--- a/src/syntax/scope.rs
+++ b/src/syntax/scope.rs
@@ -3,8 +3,7 @@
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 
-use crate::func::ParseFunc;
-use super::parsing::CallParser;
+use super::parsing::{CallParser, ParseCall};
 use super::tree::DynamicNode;
 
 /// A map from identifiers to function parsers.
@@ -17,7 +16,7 @@ impl Scope {
     /// Create a new empty scope with a fallback parser that is invoked when no
     /// match is found.
     pub fn new<F>() -> Scope
-    where F: ParseFunc<Meta=()> + DynamicNode + 'static {
+    where F: ParseCall<Meta=()> + DynamicNode + 'static {
         Scope {
             parsers: HashMap::new(),
             fallback: make_parser::<F>(()),
@@ -31,14 +30,14 @@ impl Scope {
 
     /// Associate the given name with a type that is parseable into a function.
     pub fn add<F>(&mut self, name: &str)
-    where F: ParseFunc<Meta=()> + DynamicNode + 'static {
+    where F: ParseCall<Meta=()> + DynamicNode + 'static {
         self.add_with_meta::<F>(name, ());
     }
 
     /// Add a parseable type with additional metadata  that is given to the
     /// parser (other than the default of `()`).
-    pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as ParseFunc>::Meta)
-    where F: ParseFunc + DynamicNode + 'static {
+    pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as ParseCall>::Meta)
+    where F: ParseCall + DynamicNode + 'static {
         self.parsers.insert(
             name.to_string(),
             make_parser::<F>(metadata),
@@ -64,8 +63,8 @@ impl Debug for Scope {
     }
 }
 
-fn make_parser<F>(metadata: <F as ParseFunc>::Meta) -> Box<CallParser>
-where F: ParseFunc + DynamicNode + 'static {
+fn make_parser<F>(metadata: <F as ParseCall>::Meta) -> Box<CallParser>
+where F: ParseCall + DynamicNode + 'static {
     Box::new(move |f, s| {
         F::parse(f, s, metadata.clone())
             .map(|tree| Box::new(tree) as Box<dyn DynamicNode>)
diff --git a/src/syntax/test.rs b/src/syntax/test.rs
index b701e577..504bc334 100644
--- a/src/syntax/test.rs
+++ b/src/syntax/test.rs
@@ -1,5 +1,6 @@
 use std::fmt::Debug;
 
+use crate::func::parse_maybe_body;
 use super::decoration::Decoration;
 use super::expr::{Expr, Ident, Tuple, NamedTuple, Object, Pair};
 use super::parsing::{FuncHeader, FuncArgs, FuncArg};
@@ -71,7 +72,7 @@ function! {
         header.args.key.0.clear();
         DebugFn {
             header: cloned,
-            body: body!(opt: body, state, f),
+            body: parse_maybe_body(body, state, f),
         }
     }