From aa49c0b8bb27700ab77fd8cb7231d18f4f6d2e97 Mon Sep 17 00:00:00 2001
From: Chayim Refael Friedman <chayimfr@gmail.com>
Date: Mon, 25 Aug 2025 20:19:33 +0300
Subject: [PATCH] Normalize all types when finishing inference

The new solver does not eagerly normalize, but things after inference expect types to be normalized. rustc does the same.

Also, I'm afraid other things in r-a don't expect results of the solver to be unnormalized. We'll need to handle that.
---
 .../crates/hir-ty/src/infer/unify.rs          |  3 +++
 .../hir-ty/src/tests/regression/new_solver.rs | 26 +++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
index a709aebfa9c1..bb4782bd4194 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
@@ -621,6 +621,9 @@ impl<'a> InferenceTable<'a> {
     where
         T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
     {
+        let t = self.resolve_with_fallback(t, &|_, _, d, _| d);
+        let t = self.normalize_associated_types_in(t);
+        // Resolve again, because maybe normalization inserted infer vars.
         self.resolve_with_fallback(t, &|_, _, d, _| d)
     }
 
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression/new_solver.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression/new_solver.rs
index 059f4ad32a53..20190fbc0456 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression/new_solver.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression/new_solver.rs
@@ -24,3 +24,29 @@ impl<'a> IntoIterator for &'a Grid {
         "#]],
     );
 }
+
+#[test]
+fn normalization() {
+    check_infer(
+        r#"
+//- minicore: iterator, iterators
+fn main() {
+    _ = [0i32].into_iter().filter_map(|_n| Some(1i32));
+}
+    "#,
+        expect![[r#"
+            10..69 '{     ...2)); }': ()
+            16..17 '_': FilterMap<IntoIter<i32, 1>, impl FnMut(i32) -> Option<i32>>
+            16..66 '_ = [0...1i32))': ()
+            20..26 '[0i32]': [i32; 1]
+            20..38 '[0i32]...iter()': IntoIter<i32, 1>
+            20..66 '[0i32]...1i32))': FilterMap<IntoIter<i32, 1>, impl FnMut(i32) -> Option<i32>>
+            21..25 '0i32': i32
+            50..65 '|_n| Some(1i32)': impl FnMut(i32) -> Option<i32>
+            51..53 '_n': i32
+            55..59 'Some': fn Some<i32>(i32) -> Option<i32>
+            55..65 'Some(1i32)': Option<i32>
+            60..64 '1i32': i32
+        "#]],
+    );
+}