Rollup merge of #137298 - compiler-errors:mir-wf, r=lcnr

Check signature WF when lowering MIR body

Alternative to #137233.

https://github.com/rust-lang/rust/pull/137233#issuecomment-2667879143

Fixes https://github.com/rust-lang/rust/issues/137186

We do this check in `mir_drops_elaborated_and_const_checked` and not during `mir_promoted` because that may result in borrowck cycles if WF requires looking into an opaque hidden type. This causes some TAIT tests to fail unnecessarily.

r? lcnr

try-job: test-various

compiler/rustc_hir_analysis/src/check/check.rs

@@ -745,14 +745,10 @@ fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     match tcx.def_kind(def_id) {
         DefKind::Static { .. } => {
-            tcx.ensure_ok().typeck(def_id);
-            maybe_check_static_with_link_section(tcx, def_id);
             check_static_inhabited(tcx, def_id);
             check_static_linkage(tcx, def_id);
         }
-        DefKind::Const => {
-            tcx.ensure_ok().typeck(def_id);
-        }
+        DefKind::Const => {}
         DefKind::Enum => {
             check_enum(tcx, def_id);
         }
@@ -766,7 +762,6 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
                     ExternAbi::Rust,
                 )
             }
-            // Everything else is checked entirely within check_item_body
         }
         DefKind::Impl { of_trait } => {
             if of_trait && let Some(impl_trait_header) = tcx.impl_trait_header(def_id) {

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -145,7 +145,7 @@ pub fn forbid_intrinsic_abi(tcx: TyCtxt<'_>, sp: Span, abi: ExternAbi) {
     }
 }
 
-fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
+pub(super) fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
     // Only restricted on wasm target for now
     if !tcx.sess.target.is_like_wasm {
         return;

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -201,7 +201,7 @@ fn check_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
         hir::Node::ImplItem(item) => check_impl_item(tcx, item),
         hir::Node::ForeignItem(item) => check_foreign_item(tcx, item),
         hir::Node::OpaqueTy(_) => Ok(crate::check::check::check_item_type(tcx, def_id)),
-        _ => unreachable!(),
+        _ => unreachable!("{node:?}"),
     };
 
     if let Some(generics) = node.generics() {
@@ -1108,7 +1108,13 @@ fn check_associated_item(
                 let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
-                check_sized_if_body(wfcx, item.def_id.expect_local(), ty, Some(span));
+                check_sized_if_body(
+                    wfcx,
+                    item.def_id.expect_local(),
+                    ty,
+                    Some(span),
+                    ObligationCauseCode::SizedConstOrStatic,
+                );
                 Ok(())
             }
             ty::AssocKind::Fn => {
@@ -1354,7 +1360,7 @@ fn check_item_type(
                 traits::ObligationCause::new(
                     ty_span,
                     wfcx.body_def_id,
-                    ObligationCauseCode::WellFormed(None),
+                    ObligationCauseCode::SizedConstOrStatic,
                 ),
                 wfcx.param_env,
                 item_ty,
@@ -1698,6 +1704,7 @@ fn check_fn_or_method<'tcx>(
             hir::FnRetTy::Return(ty) => Some(ty.span),
             hir::FnRetTy::DefaultReturn(_) => None,
         },
+        ObligationCauseCode::SizedReturnType,
     );
 }
 
@@ -1706,13 +1713,14 @@ fn check_sized_if_body<'tcx>(
     def_id: LocalDefId,
     ty: Ty<'tcx>,
     maybe_span: Option<Span>,
+    code: ObligationCauseCode<'tcx>,
 ) {
     let tcx = wfcx.tcx();
     if let Some(body) = tcx.hir_maybe_body_owned_by(def_id) {
         let span = maybe_span.unwrap_or(body.value.span);
 
         wfcx.register_bound(
-            ObligationCause::new(span, def_id, traits::ObligationCauseCode::SizedReturnType),
+            ObligationCause::new(span, def_id, code),
             wfcx.param_env,
             ty,
             tcx.require_lang_item(LangItem::Sized, Some(span)),

compiler/rustc_hir_analysis/src/lib.rs

@@ -212,7 +212,10 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
     tcx.par_hir_body_owners(|item_def_id| {
         let def_kind = tcx.def_kind(item_def_id);
         match def_kind {
-            DefKind::Static { .. } => tcx.ensure_ok().eval_static_initializer(item_def_id),
+            DefKind::Static { .. } => {
+                tcx.ensure_ok().eval_static_initializer(item_def_id);
+                check::maybe_check_static_with_link_section(tcx, item_def_id);
+            }
             DefKind::Const if tcx.generics_of(item_def_id).is_empty() => {
                 let instance = ty::Instance::new(item_def_id.into(), ty::GenericArgs::empty());
                 let cid = GlobalId { instance, promoted: None };
@@ -223,12 +226,9 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
         }
     });
 
-    // FIXME: Remove this when we implement creating `DefId`s
-    // for anon constants during their parents' typeck.
-    // Typeck all body owners in parallel will produce queries
-    // cycle errors because it may typeck on anon constants directly.
     tcx.par_hir_body_owners(|item_def_id| {
         let def_kind = tcx.def_kind(item_def_id);
+        // Skip `AnonConst`s because we feed their `type_of`.
         if !matches!(def_kind, DefKind::AnonConst) {
             tcx.ensure_ok().typeck(item_def_id);
         }