Let eval take code instead of markup

library/src/compute/foundations.rs

@@ -1,9 +1,5 @@
 use crate::prelude::*;
 
-use comemo::Track;
-use typst::model;
-use typst::syntax::Source;
-
 /// # Type
 /// Determine a value's type.
 ///
@@ -92,32 +88,29 @@ pub fn assert(args: &mut Args) -> SourceResult<Value> {
 }
 
 /// # Evaluate
-/// Evaluate a string as Typst markup.
+/// Evaluate a string as Typst code.
 ///
-/// You shouldn't typically need this function, but it is there if you do.
+/// This function should only be used as a last resort.
 ///
 /// ## Example
 /// ```example
-/// #let markup = "= Heading\n _Emphasis_"
-/// #eval(markup)
+/// #eval("1 + 2") \
+/// #eval("[*Strong text*]") \
+/// #eval("(1, 2, 3)").len()
 /// ```
 ///
 /// ## Parameters
 /// - source: `String` (positional, required)
-///   A string of Typst markup to evaluate.
+///   A string of Typst code to evaluate.
 ///
-///   The markup and code in the string cannot interact with the file system.
+///   The code in the string cannot interact with the file system.
 ///
-/// - returns: content
+/// - returns: any
 ///
 /// ## Category
 /// foundations
 #[func]
 pub fn eval(vm: &Vm, args: &mut Args) -> SourceResult<Value> {
     let Spanned { v: text, span } = args.expect::<Spanned<String>>("source")?;
-    let source = Source::synthesized(text, span);
-    let route = model::Route::default();
-    let mut tracer = model::Tracer::default();
-    let module = model::eval(vm.world(), route.track(), tracer.track_mut(), &source)?;
-    Ok(Value::Content(module.content()))
+    typst::model::eval_code_str(vm.world(), &text, span)
 }

src/model/eval.rs

@@ -16,7 +16,9 @@ use crate::diag::{
     bail, error, At, SourceError, SourceResult, StrResult, Trace, Tracepoint,
 };
 use crate::syntax::ast::AstNode;
-use crate::syntax::{ast, Source, SourceId, Span, Spanned, SyntaxKind, SyntaxNode};
+use crate::syntax::{
+    ast, parse_code, Source, SourceId, Span, Spanned, SyntaxKind, SyntaxNode,
+};
 use crate::util::PathExt;
 use crate::World;
 
@@ -63,6 +65,40 @@ pub fn eval(
     Ok(Module::new(name).with_scope(vm.scopes.top).with_content(result?))
 }
 
+/// Evaluate a string as code and return the resulting value.
+///
+/// Everything in the output is associated with the given `span`.
+#[comemo::memoize]
+pub fn eval_code_str(
+    world: Tracked<dyn World>,
+    text: &str,
+    span: Span,
+) -> SourceResult<Value> {
+    let mut root = parse_code(text);
+    root.synthesize(span);
+
+    let errors = root.errors();
+    if !errors.is_empty() {
+        return Err(Box::new(errors));
+    }
+
+    let id = SourceId::detached();
+    let library = world.library();
+    let scopes = Scopes::new(Some(library));
+    let route = Route::default();
+    let mut tracer = Tracer::default();
+    let mut vm = Vm::new(world, route.track(), tracer.track_mut(), id, scopes, 0);
+    let code = root.cast::<ast::Code>().unwrap();
+    let result = code.eval(&mut vm);
+
+    // Handle control flow.
+    if let Some(flow) = vm.flow {
+        bail!(flow.forbidden());
+    }
+
+    result
+}
+
 /// A virtual machine.
 ///
 /// Holds the state needed to [evaluate](eval) Typst sources. A new

src/syntax/node.rs

@@ -175,7 +175,7 @@ impl SyntaxNode {
     }
 
     /// Set a synthetic span for the node and all its descendants.
-    pub(super) fn synthesize(&mut self, span: Span) {
+    pub(crate) fn synthesize(&mut self, span: Span) {
         match &mut self.0 {
             Repr::Leaf(leaf) => leaf.span = span,
             Repr::Inner(inner) => Arc::make_mut(inner).synthesize(span),

tests/typ/compute/foundations.typ

@@ -27,14 +27,14 @@
 #test(type(10 / 3), "float")
 
 ---
-#eval("_Hello" + " World!_")
+#eval("[_Hello" + " World!_]")
 
 ---
-// Error: 7-13 expected identifier
-#eval("#let")
+// Error: 7-12 expected identifier
+#eval("let")
 
 ---
-#show raw: it => text("IBM Plex Sans", eval(it.text))
+#show raw: it => text("IBM Plex Sans", eval("[" + it.text + "]"))
 
 Interacting
 ```
@@ -43,28 +43,28 @@ Blue #move(dy: -0.15em)[🌊]
 ```
 
 ---
-// Error: 7-18 cannot continue outside of loop
-#eval("#continue")
+// Error: 7-17 cannot continue outside of loop
+#eval("continue")
 
 ---
-// Error: 7-33 cannot access file system from here
-#eval("#include \"../coma.typ\"")
+// Error: 7-32 cannot access file system from here
+#eval("include \"../coma.typ\"")
 
 ---
-// Error: 7-31 cannot access file system from here
-#eval("#image(\"/tiger.jpg\")")
+// Error: 7-30 cannot access file system from here
+#eval("image(\"/tiger.jpg\")")
 
 ---
 // Error: 23-30 cannot access file system from here
 #show raw: it => eval(it.text)
 
 ```
-#image("/tiger.jpg")
+image("/tiger.jpg")
 ```
 
 ---
-// Error: 23-30 cannot access file system from here
-#show raw: it => eval(it.text)
+// Error: 23-42 cannot access file system from here
+#show raw: it => eval("[" + it.text + "]")
 
 ```
 #show emph: _ => image("/giraffe.jpg")
@@ -72,5 +72,5 @@ _No relative giraffe!_
 ```
 
 ---
-// Error: 7-15 expected comma
-#eval("#(1 2)")
+// Error: 7-12 expected semicolon or line break
+#eval("1 2")