Rollup merge of #102489 - compiler-errors:issue-102074, r=oli-obk

Normalize substs before resolving instance in `NoopMethodCall` lint

Fixes #102074

r? types

Author: Dylan-DPC

compiler/rustc_lint/src/noop_method_call.rs

@@ -1,5 +1,4 @@
 use crate::context::LintContext;
-use crate::rustc_middle::ty::TypeVisitable;
 use crate::LateContext;
 use crate::LateLintPass;
 use rustc_errors::fluent;
@@ -46,7 +45,7 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
         };
         // We only care about method calls corresponding to the `Clone`, `Deref` and `Borrow`
         // traits and ignore any other method call.
-        let (trait_id, did) = match cx.typeck_results().type_dependent_def(expr.hir_id) {
+        let did = match cx.typeck_results().type_dependent_def(expr.hir_id) {
             // Verify we are dealing with a method/associated function.
             Some((DefKind::AssocFn, did)) => match cx.tcx.trait_of_item(did) {
                 // Check that we're dealing with a trait method for one of the traits we care about.
@@ -56,21 +55,17 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
                         Some(sym::Borrow | sym::Clone | sym::Deref)
                     ) =>
                 {
-                    (trait_id, did)
+                    did
                 }
                 _ => return,
             },
             _ => return,
         };
-        let substs = cx.typeck_results().node_substs(expr.hir_id);
-        if substs.needs_subst() {
-            // We can't resolve on types that require monomorphization, so we don't handle them if
-            // we need to perform substitution.
-            return;
-        }
-        let param_env = cx.tcx.param_env(trait_id);
+        let substs = cx
+            .tcx
+            .normalize_erasing_regions(cx.param_env, cx.typeck_results().node_substs(expr.hir_id));
         // Resolve the trait method instance.
-        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, param_env, did, substs) else {
+        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, cx.param_env, did, substs) else {
             return
         };
         // (Re)check that it implements the noop diagnostic.

src/test/ui/const-generics/generic_const_exprs/issue-102074.rs

@@ -0,0 +1,23 @@
+// check-pass
+// Checks that the NoopMethodCall lint doesn't call Instance::resolve on unresolved consts
+
+#![feature(generic_const_exprs)]
+#![allow(incomplete_features)]
+
+#[derive(Debug, Clone)]
+pub struct Aes128CipherKey([u8; Aes128Cipher::KEY_LEN]);
+
+impl Aes128CipherKey {
+    pub fn new(key: &[u8; Aes128Cipher::KEY_LEN]) -> Self {
+        Self(key.clone())
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Aes128Cipher;
+
+impl Aes128Cipher {
+    const KEY_LEN: usize = 16;
+}
+
+fn main() {}

src/test/ui/lint/noop-method-call.rs

@@ -46,6 +46,7 @@ fn main() {
 
 fn generic<T>(non_clone_type: &PlainType<T>) {
     non_clone_type.clone();
+    //~^ WARNING call to `.clone()` on a reference in this situation does nothing
 }
 
 fn non_generic(non_clone_type: &PlainType<u32>) {

src/test/ui/lint/noop-method-call.stderr

@@ -28,12 +28,20 @@ LL |     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
    = note: the type `&PlainType<u32>` which `borrow` is being called on is the same as the type returned from `borrow`, so the method call does not do anything and can be removed
 
 warning: call to `.clone()` on a reference in this situation does nothing
-  --> $DIR/noop-method-call.rs:52:19
+  --> $DIR/noop-method-call.rs:48:19
+   |
+LL |     non_clone_type.clone();
+   |                   ^^^^^^^^ unnecessary method call
+   |
+   = note: the type `&PlainType<T>` which `clone` is being called on is the same as the type returned from `clone`, so the method call does not do anything and can be removed
+
+warning: call to `.clone()` on a reference in this situation does nothing
+  --> $DIR/noop-method-call.rs:53:19
    |
 LL |     non_clone_type.clone();
    |                   ^^^^^^^^ unnecessary method call
    |
    = note: the type `&PlainType<u32>` which `clone` is being called on is the same as the type returned from `clone`, so the method call does not do anything and can be removed
 
-warning: 4 warnings emitted
+warning: 5 warnings emitted