No more lowercase for opaques

compiler/can/src/annotation.rs

@@ -1045,26 +1045,35 @@ pub fn instantiate_and_freshen_alias_type(
 pub fn freshen_opaque_def(
     var_store: &mut VarStore,
     opaque: &Alias,
-) -> (Vec<(Lowercase, Type)>, Vec<LambdaSet>, Type) {
+) -> (Vec<Variable>, Vec<LambdaSet>, Type) {
     debug_assert!(opaque.kind == AliasKind::Opaque);
 
-    let fresh_arguments = opaque
+    let fresh_variables: Vec<Variable> = opaque
         .type_variables
         .iter()
-        .map(|_| Type::Variable(var_store.fresh()))
+        .map(|_| var_store.fresh())
         .collect();
 
-    // TODO this gets ignored; is that a problem
+    let fresh_type_arguments = fresh_variables
+        .iter()
+        .copied()
+        .map(Type::Variable)
+        .collect();
+
+    // NB: We don't introduce the fresh variables here, we introduce them during constraint gen.
+    // NB: If there are bugs, check whether this is a problem!
     let mut introduced_variables = IntroducedVariables::default();
 
-    instantiate_and_freshen_alias_type(
+    let (_fresh_type_arguments, fresh_lambda_set, fresh_type) = instantiate_and_freshen_alias_type(
         var_store,
         &mut introduced_variables,
         &opaque.type_variables,
-        fresh_arguments,
+        fresh_type_arguments,
         &opaque.lambda_set_variables,
         opaque.typ.clone(),
-    )
+    );
+
+    (fresh_variables, fresh_lambda_set, fresh_type)
 }
 
 fn insertion_sort_by<T, F>(arr: &mut [T], mut compare: F)

compiler/can/src/effect_module.rs

@@ -5,7 +5,7 @@ use crate::pattern::Pattern;
 use crate::scope::Scope;
 use roc_collections::{SendMap, VecSet};
 use roc_module::called_via::CalledVia;
-use roc_module::ident::{Lowercase, TagName};
+use roc_module::ident::TagName;
 use roc_module::symbol::Symbol;
 use roc_region::all::{Loc, Region};
 use roc_types::subs::{ExhaustiveMark, RedundantMark, VarStore, Variable};
@@ -1466,7 +1466,7 @@ fn build_effect_opaque(
 
 fn build_fresh_opaque_variables(
     var_store: &mut VarStore,
-) -> (Box<Type>, Vec<(Lowercase, Type)>, Vec<LambdaSet>) {
+) -> (Box<Type>, Vec<Variable>, Vec<LambdaSet>) {
     let closure_var = var_store.fresh();
 
     // NB: if there are bugs, check whether not introducing variables is a problem!
@@ -1478,7 +1478,7 @@ fn build_fresh_opaque_variables(
         Box::new(Type::Variable(closure_var)),
         Box::new(Type::Variable(a_var)),
     );
-    let type_arguments = vec![("a".into(), Type::Variable(a_var))];
+    let type_arguments = vec![a_var];
     let lambda_set_variables = vec![roc_types::types::LambdaSet(Type::Variable(closure_var))];
 
     (Box::new(actual), type_arguments, lambda_set_variables)

compiler/can/src/expr.rs

@@ -190,7 +190,7 @@ pub enum Expr {
         // for the expression from the opaque definition. `type_arguments` is something like
         // [(n, fresh1)], and `specialized_def_type` becomes "[ Id U64 fresh1 ]".
         specialized_def_type: Box<Type>,
-        type_arguments: Vec<(Lowercase, Type)>,
+        type_arguments: Vec<Variable>,
         lambda_set_variables: Vec<LambdaSet>,
     },
 

compiler/can/src/pattern.rs

@@ -47,7 +47,7 @@ pub enum Pattern {
         // for the expression from the opaque definition. `type_arguments` is something like
         // [(n, fresh1)], and `specialized_def_type` becomes "[ Id U64 fresh1 ]".
         specialized_def_type: Box<Type>,
-        type_arguments: Vec<(Lowercase, Type)>,
+        type_arguments: Vec<Variable>,
         lambda_set_variables: Vec<LambdaSet>,
     },
     RecordDestructure {