c-variadic: reject non-extern functions

Author: folkertdev

compiler/rustc_ast_passes/messages.ftl

@@ -68,6 +68,8 @@ ast_passes_bound_in_context = bounds on `type`s in {$ctx} have no effect
 
 ast_passes_c_variadic_associated_function = associated functions cannot have a C variable argument list
 
+ast_passes_c_variadic_no_extern = `...` is not supported for non-extern functions
+
 ast_passes_const_and_c_variadic = functions cannot be both `const` and C-variadic
     .const = `const` because of this
     .variadic = C-variadic because of this

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -714,7 +714,8 @@ impl<'a> AstValidator<'a> {
                     self.dcx().emit_err(errors::BadCVariadic { span: variadic_param.span });
                 }
                 Extern::None => {
-                    self.dcx().emit_err(errors::BadCVariadic { span: variadic_param.span });
+                    let err = errors::CVariadicNoExtern { span: variadic_param.span };
+                    self.dcx().emit_err(err);
                 }
             },
             FnCtxt::Assoc(_) => {

compiler/rustc_ast_passes/src/errors.rs

@@ -325,6 +325,13 @@ pub(crate) struct CVariadicAssociatedFunction {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(ast_passes_c_variadic_no_extern)]
+pub(crate) struct CVariadicNoExtern {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(ast_passes_bad_c_variadic)]
 pub(crate) struct BadCVariadic {

tests/ui/c-variadic/issue-86053-1.rs

@@ -13,6 +13,6 @@ fn ordering4 < 'a , 'b     > ( a :            ,   self , self ,   self ,
     //~| ERROR unexpected `self` parameter in function
     //~| ERROR unexpected `self` parameter in function
     //~| ERROR `...` must be the last argument of a C-variadic function
-    //~| ERROR defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+    //~| ERROR `...` is not supported for non-extern functions
     //~| ERROR cannot find type `F` in this scope
 }

tests/ui/c-variadic/issue-86053-1.stderr

@@ -46,7 +46,7 @@ error: `...` must be the last argument of a C-variadic function
 LL |     self , ... ,   self ,   self , ... ) where F : FnOnce ( & 'a & 'b usize ) {
    |            ^^^
 
-error: defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+error: `...` is not supported for non-extern functions
   --> $DIR/issue-86053-1.rs:11:36
    |
 LL |     self , ... ,   self ,   self , ... ) where F : FnOnce ( & 'a & 'b usize ) {

tests/ui/mir/issue-83499-input-output-iteration-ice.rs

@@ -4,7 +4,6 @@
 
 fn main() {}
 
-fn foo(_: Bar, ...) -> impl {}
-//~^ ERROR defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
-//~| ERROR cannot find type `Bar` in this scope
+unsafe extern "C" fn foo(_: Bar, ...) -> impl {}
+//~^ ERROR cannot find type `Bar` in this scope
 //~| ERROR at least one trait must be specified

tests/ui/mir/issue-83499-input-output-iteration-ice.stderr

@@ -1,21 +1,15 @@
-error: defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
-  --> $DIR/issue-83499-input-output-iteration-ice.rs:7:16
-   |
-LL | fn foo(_: Bar, ...) -> impl {}
-   |                ^^^
-
 error: at least one trait must be specified
-  --> $DIR/issue-83499-input-output-iteration-ice.rs:7:24
+  --> $DIR/issue-83499-input-output-iteration-ice.rs:7:42
    |
-LL | fn foo(_: Bar, ...) -> impl {}
-   |                        ^^^^
+LL | unsafe extern "C" fn foo(_: Bar, ...) -> impl {}
+   |                                          ^^^^
 
 error[E0412]: cannot find type `Bar` in this scope
-  --> $DIR/issue-83499-input-output-iteration-ice.rs:7:11
+  --> $DIR/issue-83499-input-output-iteration-ice.rs:7:29
    |
-LL | fn foo(_: Bar, ...) -> impl {}
-   |           ^^^ not found in this scope
+LL | unsafe extern "C" fn foo(_: Bar, ...) -> impl {}
+   |                             ^^^ not found in this scope
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/parser/variadic-ffi-semantic-restrictions.rs

@@ -4,10 +4,10 @@
 fn main() {}
 
 fn f1_1(x: isize, ...) {}
-//~^ ERROR defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+//~^ ERROR `...` is not supported for non-extern functions
 
 fn f1_2(...) {}
-//~^ ERROR defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+//~^ ERROR `...` is not supported for non-extern functions
 
 extern "C" fn f2_1(x: isize, ...) {}
 //~^ ERROR defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention

tests/ui/parser/variadic-ffi-semantic-restrictions.stderr

@@ -1,10 +1,10 @@
-error: defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:6:19
    |
 LL | fn f1_1(x: isize, ...) {}
    |                   ^^^
 
-error: defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
+error: `...` is not supported for non-extern functions
   --> $DIR/variadic-ffi-semantic-restrictions.rs:9:9
    |
 LL | fn f1_2(...) {}