gccrs: Add missing ABI checking on function types

Addresses Rust-GCC#2304

gcc/rust/ChangeLog:

	* typecheck/rust-unify.cc (UnifyRules::emit_abi_mismatch): new error method
	(UnifyRules::expect_fndef): add ABI check
	* typecheck/rust-unify.h: prototype for new error method

Signed-off-by: Philip Herron <[email protected]>

Author: philberty

gcc/rust/typecheck/rust-unify.cc

@@ -126,6 +126,18 @@ UnifyRules::emit_type_mismatch () const
 		 expected->get_name ().c_str (), expr->get_name ().c_str ());
 }
 
+void
+UnifyRules::emit_abi_mismatch (const TyTy::FnType &expected,
+			       const TyTy::FnType &got) const
+{
+  RichLocation r (locus);
+  r.add_range (lhs.get_locus ());
+  r.add_range (rhs.get_locus ());
+  rust_error_at (r, "mistached abi %<%s%> got %<%s%>",
+		 get_string_from_abi (expected.get_abi ()).c_str (),
+		 get_string_from_abi (got.get_abi ()).c_str ());
+}
+
 TyTy::BaseType *
 UnifyRules::go ()
 {
@@ -912,6 +924,19 @@ UnifyRules::expect_fndef (TyTy::FnType *ltype, TyTy::BaseType *rtype)
 	    return new TyTy::ErrorType (0);
 	  }
 
+	// ABI match? see
+	// https://gcc-rust.zulipchat.com/#narrow/stream/266897-general/topic/extern.20blocks/near/346416045
+	if (ltype->get_abi () != type.get_abi ())
+	  {
+	    if (emit_error)
+	      {
+		emit_abi_mismatch (*ltype, type);
+	      }
+	    return new TyTy::ErrorType (0);
+	  }
+
+	// DEF Id match? see https://github.com/Rust-GCC/gccrs/issues/2053
+
 	return ltype->clone ();
       }
       break;

gcc/rust/typecheck/rust-unify.h

@@ -90,6 +90,8 @@ class UnifyRules
 	      std::vector<InferenceSite> &infers);
 
   void emit_type_mismatch () const;
+  void emit_abi_mismatch (const TyTy::FnType &expected,
+			  const TyTy::FnType &got) const;
 
   TyTy::BaseType *go ();