From 465844c3bee12c7a8895e6a914ab791041da2952 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Mon, 3 Feb 2025 11:42:04 +0100
Subject: [PATCH] Do not use make use of `InferenceResult::has_errors` flag for
 mir building

It generaly does not work as expected right now as we fallback type parameters to errors
---
 crates/hir-ty/src/infer.rs                    |  3 +++
 crates/hir-ty/src/method_resolution.rs        | 21 +++++++++++++++----
 crates/hir-ty/src/mir/lower.rs                |  2 +-
 .../src/handlers/incorrect_case.rs            |  2 ++
 .../src/handlers/mutability_errors.rs         |  3 ++-
 5 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/crates/hir-ty/src/infer.rs b/crates/hir-ty/src/infer.rs
index 3c258e3c4c..f4a018e2ee 100644
--- a/crates/hir-ty/src/infer.rs
+++ b/crates/hir-ty/src/infer.rs
@@ -466,6 +466,9 @@ pub struct InferenceResult {
     pub type_of_for_iterator: FxHashMap<ExprId, Ty>,
     type_mismatches: FxHashMap<ExprOrPatId, TypeMismatch>,
     /// Whether there are any type-mismatching errors in the result.
+    // FIXME: This isn't as useful as initially thought due to us falling back placeholders to
+    // `TyKind::Error`.
+    // Which will then mark this field.
     pub(crate) has_errors: bool,
     /// Interned common types to return references to.
     // FIXME: Move this into `InferenceContext`
diff --git a/crates/hir-ty/src/method_resolution.rs b/crates/hir-ty/src/method_resolution.rs
index 1cea67ee96..db94351dcc 100644
--- a/crates/hir-ty/src/method_resolution.rs
+++ b/crates/hir-ty/src/method_resolution.rs
@@ -4,6 +4,7 @@
 //! and the corresponding code mostly in rustc_hir_analysis/check/method/probe.rs.
 use std::ops::ControlFlow;
 
+use arrayvec::ArrayVec;
 use base_db::CrateId;
 use chalk_ir::{cast::Cast, UniverseIndex, WithKind};
 use hir_def::{
@@ -732,15 +733,27 @@ fn lookup_impl_assoc_item_for_trait_ref(
     let self_ty = trait_ref.self_type_parameter(Interner);
     let self_ty_fp = TyFingerprint::for_trait_impl(&self_ty)?;
     let impls = db.trait_impls_in_deps(env.krate);
-    let self_impls = match self_ty.kind(Interner) {
-        TyKind::Adt(id, _) => {
-            id.0.module(db.upcast()).containing_block().and_then(|it| db.trait_impls_in_block(it))
+
+    let trait_module = hir_trait_id.module(db.upcast());
+    let type_module = match self_ty_fp {
+        TyFingerprint::Adt(adt_id) => Some(adt_id.module(db.upcast())),
+        TyFingerprint::ForeignType(type_id) => {
+            Some(from_foreign_def_id(type_id).module(db.upcast()))
         }
+        TyFingerprint::Dyn(trait_id) => Some(trait_id.module(db.upcast())),
         _ => None,
     };
+
+    let def_blocks: ArrayVec<_, 2> =
+        [trait_module.containing_block(), type_module.and_then(|it| it.containing_block())]
+            .into_iter()
+            .flatten()
+            .filter_map(|block_id| db.trait_impls_in_block(block_id))
+            .collect();
+
     let impls = impls
         .iter()
-        .chain(self_impls.as_ref())
+        .chain(&def_blocks)
         .flat_map(|impls| impls.for_trait_and_self_ty(hir_trait_id, self_ty_fp));
 
     let table = InferenceTable::new(db, env);
diff --git a/crates/hir-ty/src/mir/lower.rs b/crates/hir-ty/src/mir/lower.rs
index cc6ed122af..549450e9be 100644
--- a/crates/hir-ty/src/mir/lower.rs
+++ b/crates/hir-ty/src/mir/lower.rs
@@ -2156,7 +2156,7 @@ pub fn lower_to_mir(
     // need to take this input explicitly.
     root_expr: ExprId,
 ) -> Result<MirBody> {
-    if infer.has_errors {
+    if infer.type_mismatches().next().is_some() {
         return Err(MirLowerError::HasErrors);
     }
     let mut ctx = MirLowerCtx::new(db, owner, body, infer);
diff --git a/crates/ide-diagnostics/src/handlers/incorrect_case.rs b/crates/ide-diagnostics/src/handlers/incorrect_case.rs
index 0cc80bda2c..246330e6ef 100644
--- a/crates/ide-diagnostics/src/handlers/incorrect_case.rs
+++ b/crates/ide-diagnostics/src/handlers/incorrect_case.rs
@@ -936,6 +936,7 @@ fn func() {
     fn override_lint_level() {
         check_diagnostics(
             r#"
+#![allow(unused_variables)]
 #[warn(nonstandard_style)]
 fn foo() {
     let BAR;
@@ -992,6 +993,7 @@ struct QUX;
 const foo: i32 = 0;
 fn BAR() {
     let BAZ;
+    _ = BAZ;
 }
         "#,
         );
diff --git a/crates/ide-diagnostics/src/handlers/mutability_errors.rs b/crates/ide-diagnostics/src/handlers/mutability_errors.rs
index 1397979144..0e3c4c7aa3 100644
--- a/crates/ide-diagnostics/src/handlers/mutability_errors.rs
+++ b/crates/ide-diagnostics/src/handlers/mutability_errors.rs
@@ -831,13 +831,14 @@ fn f() {
 
     #[test]
     fn or_pattern() {
-        // FIXME: `None` is inferred as unknown here for some reason
         check_diagnostics(
             r#"
 //- minicore: option
 fn f(_: i32) {}
 fn main() {
     let ((Some(mut x), None) | (_, Some(mut x))) = (None, Some(7)) else { return };
+             //^^^^^ 💡 warn: variable does not need to be mutable
+
     f(x);
 }
 "#,