Stop exporting TypeckRootCtxt and FnCtxt.

While they have many convenient APIs, it is better to expose dedicated functions for them

clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -12,7 +12,6 @@ use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{BorrowKind, Expr, ExprKind, ItemKind, LangItem, Node};
-use rustc_hir_typeck::{FnCtxt, TypeckRootCtxt};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::mir::Mutability;
@@ -437,9 +436,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
             Node::Item(item) => {
                 if let ItemKind::Fn(_, _, body_id) = &item.kind
                     && let output_ty = return_ty(cx, item.owner_id)
-                    && let root_ctxt = TypeckRootCtxt::new(cx.tcx, item.owner_id.def_id)
-                    && let fn_ctxt = FnCtxt::new(&root_ctxt, cx.param_env, item.owner_id.def_id)
-                    && fn_ctxt.can_coerce(ty, output_ty)
+                    && rustc_hir_typeck::can_coerce(cx.tcx, cx.param_env, item.owner_id.def_id, ty, output_ty)
                 {
                     if has_lifetime(output_ty) && has_lifetime(ty) {
                         return false;

clippy_lints/src/transmute/transmutes_expressible_as_ptr_casts.rs

@@ -1,4 +1,4 @@
-use super::utils::check_cast;
+use rustc_hir_typeck::cast::check_cast;
 use super::TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::sugg::Sugg;
@@ -22,7 +22,7 @@ pub(super) fn check<'tcx>(
 ) -> bool {
     use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast};
     let mut app = Applicability::MachineApplicable;
-    let mut sugg = match check_cast(cx, e, from_ty, to_ty) {
+    let mut sugg = match check_cast(cx.tcx, cx.param_env, e, from_ty, to_ty) {
         Some(FnPtrAddrCast | PtrAddrCast) if const_context => return false,
         Some(PtrPtrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast) => {
             Sugg::hir_with_context(cx, arg, e.span.ctxt(), "..", &mut app)

clippy_lints/src/transmute/utils.rs

@@ -1,10 +1,5 @@
-use rustc_hir as hir;
-use rustc_hir::Expr;
-use rustc_hir_typeck::{cast, FnCtxt, TypeckRootCtxt};
 use rustc_lint::LateContext;
-use rustc_middle::ty::cast::CastKind;
 use rustc_middle::ty::Ty;
-use rustc_span::DUMMY_SP;
 
 // check if the component types of the transmuted collection and the result have different ABI,
 // size or alignment
@@ -20,35 +15,3 @@ pub(super) fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx
         false
     }
 }
-
-/// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of
-/// the cast. In certain cases, including some invalid casts from array references
-/// to pointers, this may cause additional errors to be emitted and/or ICE error
-/// messages. This function will panic if that occurs.
-pub(super) fn check_cast<'tcx>(
-    cx: &LateContext<'tcx>,
-    e: &'tcx Expr<'_>,
-    from_ty: Ty<'tcx>,
-    to_ty: Ty<'tcx>,
-) -> Option<CastKind> {
-    let hir_id = e.hir_id;
-    let local_def_id = hir_id.owner.def_id;
-
-    let root_ctxt = TypeckRootCtxt::new(cx.tcx, local_def_id);
-    let fn_ctxt = FnCtxt::new(&root_ctxt, cx.param_env, local_def_id);
-
-    if let Ok(check) = cast::CastCheck::new(
-        &fn_ctxt,
-        e,
-        from_ty,
-        to_ty,
-        // We won't show any error to the user, so we don't care what the span is here.
-        DUMMY_SP,
-        DUMMY_SP,
-        hir::Constness::NotConst,
-    ) {
-        check.do_check(&fn_ctxt).ok()
-    } else {
-        None
-    }
-}