gccrs: Add variadic check on function params

gcc/rust/ChangeLog:

	* checks/errors/rust-ast-validation.cc (ASTValidation::visit):
	Add variadic check on all parameters.

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2850.rs: New test.

Signed-off-by: 0xn4utilus <gyanendrabanjare8@gmail.com>

gcc/rust/checks/errors/rust-ast-validation.cc

@@ -132,10 +132,14 @@ ASTValidation::visit (AST::Function &function)
 	rust_error_at (function.get_locus (), "free function without a body");
     }
 
-  if (function.is_variadic ())
-    rust_error_at (
-      function.get_function_params ().back ()->get_locus (),
-      "only foreign or %<unsafe extern \"C\"%> functions may be C-variadic");
+  auto &function_params = function.get_function_params ();
+  for (auto it = function_params.begin (); it != function_params.end (); it++)
+    {
+      if (it->get ()->is_variadic ())
+	rust_error_at (it->get ()->get_locus (),
+		       "only foreign or %<unsafe extern \"C\"%> functions may "
+		       "be C-variadic");
+    }
 
   AST::ContextualASTVisitor::visit (function);
 }

gcc/testsuite/rust/compile/issue-2850.rs

+fn myfun0(...,_:i32) {}
+// { dg-error "only foreign or .unsafe extern \"C\". functions may be C-variadic" "" { target *-*-* } .-1 }
+
+fn myfun1(a:i32,...,_:i32) {}
+// { dg-error "only foreign or .unsafe extern \"C\". functions may be C-variadic" "" { target *-*-* } .-1 }
+
+struct z {
+    x: f64,
+    y: f64,
+}
+
+impl z {
+    fn new(x: f64, ..., y: f64) -> z {
+        // { dg-error "only foreign or .unsafe extern \"C\". functions may be C-variadic" "" { target *-*-* } .-1 }
+        z { x: x, y: y }
+    }
+}
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