Parse assumptions

crates/frontend/src/ast.rs

@@ -23,8 +23,6 @@ use strum::{EnumDiscriminants, EnumIter};
 
 use crate::prelude::*;
 
-// TODO: migrate AST logic (after redesigning grammar)
-
 /// Retrieves, but does not parse, all top-level items in a file.
 // TODO: is `Vec` the most efficient to incrementally update here?
 #[salsa::tracked]
@@ -186,14 +184,19 @@ pub fn import<'db>(db: &'db dyn Database, ast: AstNode) -> Import<'db> {
 pub struct Import<'db> {}
 
 /// Parses [Assumption] from an [AstNode].
+// TODO: parse soft weights
 #[salsa::tracked]
 pub fn assumption<'db>(db: &'db dyn Database, ast: AstNode) -> Assumption<'db> {
-    todo!()
+    let body = rule_body(db, ast.expect_field(db, "body"));
+    Assumption::new(db, body)
 }
 
 /// An abstract assumption.
 #[salsa::tracked]
-pub struct Assumption<'db> {}
+pub struct Assumption<'db> {
+    /// The assumption's rule body.
+    pub body: RuleBody<'db>,
+}
 
 /// Parses a rule body.
 // TODO: parallelize?