Shove more into a common env

crates/compiler/solve/src/env.rs

@@ -0,0 +1,75 @@
+use bumpalo::Bump;
+use roc_can::{constraint::Constraints, module::ExposedByModule};
+use roc_derive::SharedDerivedModule;
+use roc_types::subs::{Content, Descriptor, Mark, OptVariable, Rank, Subs, Variable};
+
+use crate::Pools;
+
+pub struct DerivedEnv<'a> {
+    pub derived_module: &'a SharedDerivedModule,
+    /// Exposed types needed by the derived module.
+    pub exposed_types: &'a ExposedByModule,
+}
+
+pub struct Env<'a> {
+    pub arena: &'a Bump,
+    pub constraints: &'a Constraints,
+    pub derived_env: &'a DerivedEnv<'a>,
+    pub subs: &'a mut Subs,
+    pub pools: &'a mut Pools,
+}
+
+impl<'a> Env<'a> {
+    #[inline(always)]
+    pub fn register(&mut self, rank: Rank, content: Content) -> Variable {
+        let descriptor = Descriptor {
+            content,
+            rank,
+            mark: Mark::NONE,
+            copy: OptVariable::NONE,
+        };
+
+        let var = self.subs.fresh(descriptor);
+
+        self.pools.get_mut(rank).push(var);
+
+        var
+    }
+
+    /// Introduce some variables to Pools at the given rank.
+    /// Also, set each of their ranks in Subs to be the given rank.
+    pub fn introduce(&mut self, rank: Rank, vars: &[Variable]) {
+        let pool: &mut Vec<Variable> = self.pools.get_mut(rank);
+
+        for &var in vars.iter() {
+            self.subs.set_rank(var, rank);
+        }
+
+        pool.extend(vars);
+    }
+
+    #[inline(always)]
+    pub fn register_existing_var(&mut self, var: Variable) {
+        self.pools.get_mut(self.subs.get_rank(var)).push(var);
+    }
+
+    pub fn register_with_known_var(
+        &mut self,
+        var: Variable,
+        rank: Rank,
+        content: Content,
+    ) -> Variable {
+        let descriptor = Descriptor {
+            content,
+            rank,
+            mark: Mark::NONE,
+            copy: OptVariable::NONE,
+        };
+
+        self.subs.set(var, descriptor);
+
+        self.pools.get_mut(rank).push(var);
+
+        var
+    }
+}