Separate Program from ProgramEnvironment.

Closes #19. I took a slightly different approach from your suggestion.

ir::Program and ProgramEnvironment are distinct types with no ownership
relationship, but instead of lowering returning a tuple, ir::Program
has a method to construct a ProgramEnvironment.

In addition to the trait_data, the associated_type_data also needs to
be cloned over, and the `split_projection` method is duplicated for
both types, because that method is invoked in `elaborated_clauses`.

It seems like once we have a new way of solving #12, ProgramEnvironment
would just be a set of ProgramClauses, and that would be the whole
context necessary for the solver to run.

Author: withoutboats

chalk-rust/src/ir/mod.rs

@@ -12,6 +12,9 @@ pub struct Program {
     /// For each struct/trait:
     pub type_kinds: HashMap<ItemId, TypeKind>,
 
+    /// For each struct:
+    pub struct_data: HashMap<ItemId, StructDatum>,
+
     /// For each impl:
     pub impl_data: HashMap<ItemId, ImplDatum>,
 
@@ -20,12 +23,34 @@ pub struct Program {
 
     /// For each trait:
     pub associated_ty_data: HashMap<ItemId, AssociatedTyDatum>,
+}
+
+impl Program {
+    pub fn split_projection<'p>(&self, projection: &'p ProjectionTy)
+                            -> (&AssociatedTyDatum, &'p [Parameter], &'p [Parameter]) {
+        let ProjectionTy { associated_ty_id, ref parameters } = *projection;
+        let associated_ty_data = &self.associated_ty_data[&associated_ty_id];
+        let trait_datum = &self.trait_data[&associated_ty_data.trait_id];
+        let trait_num_params = trait_datum.binders.len();
+        let split_point = parameters.len() - trait_num_params;
+        let (other_params, trait_params) = parameters.split_at(split_point);
+        (associated_ty_data, trait_params, other_params)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProgramEnvironment {
+    /// For each trait:
+    pub trait_data: HashMap<ItemId, TraitDatum>,
+
+    /// For each trait:
+    pub associated_ty_data: HashMap<ItemId, AssociatedTyDatum>,
 
     /// Compiled forms of the above:
     pub program_clauses: Vec<ProgramClause>,
 }
 
-impl Program {
+impl ProgramEnvironment {
     pub fn split_projection<'p>(&self, projection: &'p ProjectionTy)
                             -> (&AssociatedTyDatum, &'p [Parameter], &'p [Parameter]) {
         let ProjectionTy { associated_ty_id, ref parameters } = *projection;

chalk-rust/src/lower/mod.rs

@@ -225,33 +225,7 @@ impl LowerProgram for Program {
             }
         }
 
-        // Construct the set of *clauses*; these are sort of a compiled form
-        // of the data above that always has the form:
-        //
-        //       forall P0...Pn. Something :- Conditions
-        let mut program_clauses = vec![];
-
-        for struct_datum in struct_data.values() {
-            program_clauses.extend(struct_datum.to_program_clauses());
-        }
-
-        for trait_datum in trait_data.values() {
-            program_clauses.extend(trait_datum.to_program_clauses());
-        }
-
-        for (&id, associated_ty_datum) in &associated_ty_data {
-            program_clauses.extend(associated_ty_datum.to_program_clauses(id));
-        }
-
-        for impl_datum in impl_data.values() {
-            program_clauses.push(impl_datum.to_program_clause());
-
-            for atv in &impl_datum.binders.value.associated_ty_values {
-                program_clauses.extend(atv.to_program_clauses(impl_datum));
-            }
-        }
-
-        Ok(ir::Program { type_ids, type_kinds, trait_data, impl_data, associated_ty_data, program_clauses })
+        Ok(ir::Program { type_ids, type_kinds, struct_data, trait_data, impl_data, associated_ty_data, })
     }
 }
 
@@ -882,6 +856,34 @@ impl LowerQuantifiedGoal for Goal {
     }
 }
 
+impl ir::Program {
+    pub fn environment(&self) -> ir::ProgramEnvironment {
+        // Construct the set of *clauses*; these are sort of a compiled form
+        // of the data above that always has the form:
+        //
+        //       forall P0...Pn. Something :- Conditions
+        let mut program_clauses = vec![];
+
+        program_clauses.extend(self.struct_data.values().flat_map(|d| d.to_program_clauses()));
+        program_clauses.extend(self.trait_data.values().flat_map(|d| d.to_program_clauses()));
+        program_clauses.extend(self.associated_ty_data.iter().flat_map(|(&id, d)| {
+            d.to_program_clauses(id)
+        }));
+
+        for datum in self.impl_data.values() {
+            program_clauses.push(datum.to_program_clause());
+            program_clauses.extend(datum.binders.value.associated_ty_values.iter().flat_map(|atv| {
+                atv.to_program_clauses(datum)
+            }));
+        }
+
+        let trait_data = self.trait_data.clone();
+        let associated_ty_data = self.associated_ty_data.clone();
+
+        ir::ProgramEnvironment { trait_data, associated_ty_data, program_clauses }
+    }
+}
+
 impl ir::ImplDatum {
     /// Given `impl<T: Clone> Clone for Vec<T>`, generate:
     ///

chalk-rust/src/solve/environment.rs

@@ -29,7 +29,7 @@ impl Environment {
         Arc::new(env)
     }
 
-    pub fn elaborated_clauses(&self, program: &Program) -> impl Iterator<Item = WhereClause> {
+    pub fn elaborated_clauses(&self, program: &ProgramEnvironment) -> impl Iterator<Item = WhereClause> {
         let mut set = HashSet::new();
         set.extend(self.clauses.iter().cloned());
 

chalk-rust/src/solve/fulfill.rs

@@ -23,7 +23,7 @@ impl<'s> Fulfill<'s> {
         Fulfill { solver, infer, obligations: vec![], constraints: HashSet::new() }
     }
 
-    pub fn program(&self) -> Arc<Program> {
+    pub fn program(&self) -> Arc<ProgramEnvironment> {
         self.solver.program.clone()
     }
 

chalk-rust/src/solve/solver/mod.rs

@@ -13,13 +13,13 @@ use std::sync::Arc;
 use super::*;
 
 pub struct Solver {
-    pub(super) program: Arc<Program>,
+    pub(super) program: Arc<ProgramEnvironment>,
     overflow_depth: usize,
     stack: Vec<Query<InEnvironment<WhereClauseGoal>>>,
 }
 
 impl Solver {
-    pub fn new(program: &Arc<Program>, overflow_depth: usize) -> Self {
+    pub fn new(program: &Arc<ProgramEnvironment>, overflow_depth: usize) -> Self {
         Solver { program: program.clone(), stack: vec![], overflow_depth, }
     }
 

chalk-rust/src/solve/test.rs

@@ -27,6 +27,7 @@ fn solve_goal(program_text: &str,
     assert!(program_text.starts_with("{"));
     assert!(program_text.ends_with("}"));
     let program = Arc::new(parse_and_lower_program(&program_text[1..program_text.len()-1]).unwrap());
+    let env = Arc::new(program.environment());
     ir::set_current_program(&program, || {
         for (goal_text, expected) in goals {
             println!("----------------------------------------------------------------------");
@@ -39,7 +40,7 @@ fn solve_goal(program_text: &str,
             // tests don't require a higher one.
             let overflow_depth = 3;
 
-            let mut solver = Solver::new(&program, overflow_depth);
+            let mut solver = Solver::new(&env, overflow_depth);
             let result = match Prove::new(&mut solver, goal).solve() {
                 Ok(v) => format!("{:#?}", v),
                 Err(e) => format!("{}", e),