Rollup merge of #138964 - compiler-errors:usage-of-interner, r=lcnr

Implement lint against using Interner and InferCtxtLike in random compiler crates

Often `Interner` defines similar methods to `TyCtxt` (but often simplified due to the simpler API surface of the type system layer for the new solver), which people will either unintentionally or intentionally import and use. Let's discourage that.

r? lcnr

tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.rs

@@ -0,0 +1,16 @@
+//@ compile-flags: -Z unstable-options
+//@ ignore-stage1
+
+#![feature(rustc_private)]
+#![deny(rustc::usage_of_type_ir_traits)]
+
+extern crate rustc_type_ir;
+
+use rustc_type_ir::Interner;
+
+fn foo<I: Interner>(cx: I, did: I::DefId) {
+    let _ = cx.trait_is_unsafe(did);
+    //~^ ERROR do not use `rustc_type_ir::Interner` or `rustc_type_ir::InferCtxtLike` unless you're inside of the trait solver
+}
+
+fn main() {}

tests/ui-fulldeps/internal-lints/import-of-type-ir-traits.stderr

@@ -0,0 +1,15 @@
+error: do not use `rustc_type_ir::Interner` or `rustc_type_ir::InferCtxtLike` unless you're inside of the trait solver
+  --> $DIR/import-of-type-ir-traits.rs:12:13
+   |
+LL |     let _ = cx.trait_is_unsafe(did);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the method or struct you're looking for is likely defined somewhere else downstream in the compiler
+note: the lint level is defined here
+  --> $DIR/import-of-type-ir-traits.rs:5:9
+   |
+LL | #![deny(rustc::usage_of_type_ir_traits)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+