From 4473f3549f331c51a7df0e307d356a06c00d7288 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 7 Dec 2020 19:02:07 +0000
Subject: Resolve imports and alternatives outside of the ast traversal

---
 dhall/src/semantics/resolve/hir.rs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

(limited to 'dhall/src/semantics/resolve/hir.rs')

diff --git a/dhall/src/semantics/resolve/hir.rs b/dhall/src/semantics/resolve/hir.rs
index 05a8550..8baad10 100644
--- a/dhall/src/semantics/resolve/hir.rs
+++ b/dhall/src/semantics/resolve/hir.rs
@@ -1,7 +1,7 @@
 use crate::error::TypeError;
 use crate::semantics::{type_with, typecheck, NameEnv, Nir, NzEnv, Tir, TyEnv};
 use crate::syntax::{Expr, ExprKind, Span, V};
-use crate::{Ctxt, ImportId, ToExprOptions};
+use crate::{Ctxt, ImportAlternativeId, ImportId, ToExprOptions};
 
 /// Stores an alpha-normalized variable.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -15,8 +15,10 @@ pub enum HirKind<'cx> {
     Var(AlphaVar),
     /// A variable that couldn't be resolved. Detected during resolution, but causes an error during typeck.
     MissingVar(V),
-    /// An import. It must have been resolved by the time we get to typechecking/normalization.
+    /// An import. It must have been resolved after resolution.
     Import(ImportId<'cx>),
+    /// An import alternative. It must have been decided after resolution.
+    ImportAlternative(ImportAlternativeId<'cx>, Hir<'cx>, Hir<'cx>),
     // Forbidden ExprKind variants: Var, Import, Completion
     Expr(ExprKind<Hir<'cx>>),
 }
@@ -111,6 +113,14 @@ fn hir_to_expr<'cx>(
             let typed = cx[import].unwrap_result();
             return hir_to_expr(cx, &typed.hir, opts, &mut NameEnv::new());
         }
+        HirKind::ImportAlternative(alt, left, right) => {
+            let hir = if cx[alt].unwrap_selected() {
+                left
+            } else {
+                right
+            };
+            return hir_to_expr(cx, hir, opts, env);
+        }
         HirKind::Expr(e) => {
             let e = e.map_ref_maybe_binder(|l, hir| {
                 if let Some(l) = l {
-- 
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