Auto merge of #87114 - cjgillot:abilint, r=estebank

Lint missing Abi in ast validation instead of lowering.

6 files changed, 61 insertions, 50 deletions

diff --git a/Cargo.lock b/Cargo.lock
index f49c8515fca..5b8d28752b4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3556,6 +3556,7 @@ dependencies = [
  "rustc_parse",
  "rustc_session",
  "rustc_span",
+ "rustc_target",
  "tracing",
 ]
 
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 8daeef0cbd9..162b59777ca 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -279,7 +279,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     );
                     let sig = hir::FnSig {
                         decl,
-                        header: this.lower_fn_header(header, fn_sig_span, id),
+                        header: this.lower_fn_header(header),
                         span: this.lower_span(fn_sig_span),
                     };
                     hir::ItemKind::Fn(sig, generics, body_id)
@@ -291,17 +291,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
             },
-            ItemKind::ForeignMod(ref fm) => {
-                if fm.abi.is_none() {
-                    self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
-                }
-                hir::ItemKind::ForeignMod {
-                    abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
-                    items: self
-                        .arena
-                        .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
-                }
-            }
+            ItemKind::ForeignMod(ref fm) => hir::ItemKind::ForeignMod {
+                abi: fm.abi.map_or(abi::Abi::FALLBACK, |abi| self.lower_abi(abi)),
+                items: self
+                    .arena
+                    .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
+            },
             ItemKind::GlobalAsm(ref asm) => {
                 hir::ItemKind::GlobalAsm(self.lower_inline_asm(span, asm))
             }
@@ -807,7 +802,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, None)) => {
                 let names = self.lower_fn_params_to_names(&sig.decl);
                 let (generics, sig) =
-                    self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
+                    self.lower_method_sig(generics, sig, trait_item_def_id, false, None);
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)))
             }
             AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, Some(ref body))) => {
@@ -820,7 +815,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     trait_item_def_id,
                     false,
                     asyncness.opt_return_id(),
-                    i.id,
                 );
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)))
             }
@@ -897,7 +891,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     impl_item_def_id,
                     impl_trait_return_allow,
                     asyncness.opt_return_id(),
-                    i.id,
                 );
 
                 (generics, hir::ImplItemKind::Fn(sig, body_id))
@@ -1292,9 +1285,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         fn_def_id: LocalDefId,
         impl_trait_return_allow: bool,
         is_async: Option<NodeId>,
-        id: NodeId,
     ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
-        let header = self.lower_fn_header(sig.header, sig.span, id);
+        let header = self.lower_fn_header(sig.header);
         let (generics, decl) = self.add_in_band_defs(
             generics,
             fn_def_id,
@@ -1311,12 +1303,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
     }
 
-    fn lower_fn_header(&mut self, h: FnHeader, span: Span, id: NodeId) -> hir::FnHeader {
+    fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
         hir::FnHeader {
             unsafety: self.lower_unsafety(h.unsafety),
             asyncness: self.lower_asyncness(h.asyncness),
             constness: self.lower_constness(h.constness),
-            abi: self.lower_extern(h.ext, span, id),
+            abi: self.lower_extern(h.ext),
         }
     }
 
@@ -1327,13 +1319,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         })
     }
 
-    pub(super) fn lower_extern(&mut self, ext: Extern, span: Span, id: NodeId) -> abi::Abi {
+    pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
         match ext {
             Extern::None => abi::Abi::Rust,
-            Extern::Implicit => {
-                self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
-                abi::Abi::C { unwind: false }
-            }
+            Extern::Implicit => abi::Abi::FALLBACK,
             Extern::Explicit(abi) => self.lower_abi(abi),
         }
     }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index deb7e742e5c..fc953279c46 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -53,7 +53,7 @@ use rustc_hir::definitions::{DefKey, DefPathData, Definitions};
 use rustc_hir::intravisit;
 use rustc_hir::{ConstArg, GenericArg, InferKind, ParamName};
 use rustc_index::vec::{Idx, IndexVec};
-use rustc_session::lint::builtin::{BARE_TRAIT_OBJECTS, MISSING_ABI};
+use rustc_session::lint::builtin::BARE_TRAIT_OBJECTS;
 use rustc_session::lint::{BuiltinLintDiagnostics, LintBuffer};
 use rustc_session::utils::{FlattenNonterminals, NtToTokenstream};
 use rustc_session::Session;
@@ -62,7 +62,6 @@ use rustc_span::hygiene::ExpnId;
 use rustc_span::source_map::{respan, CachingSourceMapView, DesugaringKind};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::spec::abi::Abi;
 
 use smallvec::SmallVec;
 use std::collections::BTreeMap;
@@ -1361,7 +1360,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
             TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(&f.generic_params, |this| {
                 this.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
-                    let span = this.sess.source_map().next_point(t.span.shrink_to_lo());
                     hir::TyKind::BareFn(this.arena.alloc(hir::BareFnTy {
                         generic_params: this.lower_generic_params(
                             &f.generic_params,
@@ -1369,7 +1367,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             ImplTraitContext::disallowed(),
                         ),
                         unsafety: this.lower_unsafety(f.unsafety),
-                        abi: this.lower_extern(f.ext, span, t.id),
+                        abi: this.lower_extern(f.ext),
                         decl: this.lower_fn_decl(&f.decl, None, false, None),
                         param_names: this.lower_fn_params_to_names(&f.decl),
                     }))
@@ -2749,26 +2747,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
     }
-
-    fn maybe_lint_missing_abi(&mut self, span: Span, id: NodeId, default: Abi) {
-        // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
-        // call site which do not have a macro backtrace. See #61963.
-        let is_macro_callsite = self
-            .sess
-            .source_map()
-            .span_to_snippet(span)
-            .map(|snippet| snippet.starts_with("#["))
-            .unwrap_or(true);
-        if !is_macro_callsite {
-            self.resolver.lint_buffer().buffer_lint_with_diagnostic(
-                MISSING_ABI,
-                id,
-                span,
-                "extern declarations without an explicit ABI are deprecated",
-                BuiltinLintDiagnostics::MissingAbi(span, default),
-            )
-        }
-    }
 }
 
 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body<'_>>) -> Vec<hir::BodyId> {
diff --git a/compiler/rustc_ast_passes/Cargo.toml b/compiler/rustc_ast_passes/Cargo.toml
index 6b931c598ed..4a6eb80fb30 100644
--- a/compiler/rustc_ast_passes/Cargo.toml
+++ b/compiler/rustc_ast_passes/Cargo.toml
@@ -14,4 +14,5 @@ rustc_feature = { path = "../rustc_feature" }
 rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
+rustc_target = { path = "../rustc_target" }
 rustc_ast = { path = "../rustc_ast" }
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index a243300edd9..aca4503903c 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -15,12 +15,13 @@ use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{error_code, pluralize, struct_span_err, Applicability};
 use rustc_parse::validate_attr;
-use rustc_session::lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY;
+use rustc_session::lint::builtin::{MISSING_ABI, PATTERNS_IN_FNS_WITHOUT_BODY};
 use rustc_session::lint::{BuiltinLintDiagnostics, LintBuffer};
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Span;
+use rustc_target::spec::abi;
 use std::mem;
 use std::ops::DerefMut;
 
@@ -844,6 +845,10 @@ impl<'a> AstValidator<'a> {
                     .emit();
                 });
                 self.check_late_bound_lifetime_defs(&bfty.generic_params);
+                if let Extern::Implicit = bfty.ext {
+                    let sig_span = self.session.source_map().next_point(ty.span.shrink_to_lo());
+                    self.maybe_lint_missing_abi(sig_span, ty.id);
+                }
             }
             TyKind::TraitObject(ref bounds, ..) => {
                 let mut any_lifetime_bounds = false;
@@ -894,6 +899,26 @@ impl<'a> AstValidator<'a> {
             _ => {}
         }
     }
+
+    fn maybe_lint_missing_abi(&mut self, span: Span, id: NodeId) {
+        // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
+        // call site which do not have a macro backtrace. See #61963.
+        let is_macro_callsite = self
+            .session
+            .source_map()
+            .span_to_snippet(span)
+            .map(|snippet| snippet.starts_with("#["))
+            .unwrap_or(true);
+        if !is_macro_callsite {
+            self.lint_buffer.buffer_lint_with_diagnostic(
+                MISSING_ABI,
+                id,
+                span,
+                "extern declarations without an explicit ABI are deprecated",
+                BuiltinLintDiagnostics::MissingAbi(span, abi::Abi::FALLBACK),
+            )
+        }
+    }
 }
 
 /// Checks that generic parameters are in the correct order,
@@ -1178,7 +1203,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
-            ItemKind::ForeignMod(ForeignMod { unsafety, .. }) => {
+            ItemKind::ForeignMod(ForeignMod { abi, unsafety, .. }) => {
                 let old_item = mem::replace(&mut self.extern_mod, Some(item));
                 self.invalid_visibility(
                     &item.vis,
@@ -1187,6 +1212,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 if let Unsafe::Yes(span) = unsafety {
                     self.err_handler().span_err(span, "extern block cannot be declared unsafe");
                 }
+                if abi.is_none() {
+                    self.maybe_lint_missing_abi(item.span, item.id);
+                }
                 visit::walk_item(self, item);
                 self.extern_mod = old_item;
                 return; // Avoid visiting again.
@@ -1526,6 +1554,17 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 .emit();
         }
 
+        if let FnKind::Fn(
+            _,
+            _,
+            FnSig { span: sig_span, header: FnHeader { ext: Extern::Implicit, .. }, .. },
+            _,
+            _,
+        ) = fk
+        {
+            self.maybe_lint_missing_abi(*sig_span, id);
+        }
+
         // Functions without bodies cannot have patterns.
         if let FnKind::Fn(ctxt, _, sig, _, None) = fk {
             Self::check_decl_no_pat(&sig.decl, |span, ident, mut_ident| {
diff --git a/compiler/rustc_target/src/spec/abi.rs b/compiler/rustc_target/src/spec/abi.rs
index ee36090c549..e3a2226eb9d 100644
--- a/compiler/rustc_target/src/spec/abi.rs
+++ b/compiler/rustc_target/src/spec/abi.rs
@@ -87,6 +87,9 @@ pub fn all_names() -> Vec<&'static str> {
 }
 
 impl Abi {
+    /// Default ABI chosen for `extern fn` declarations without an explicit ABI.
+    pub const FALLBACK: Abi = Abi::C { unwind: false };
+
     #[inline]
     pub fn index(self) -> usize {
         // N.B., this ordering MUST match the AbiDatas array above.