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Rollup merge of rust-lang#133538 - dev-ardi:69232-better-diag, r=comp…
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…iler-errors

Better diagnostic for fn items in variadic functions

closes rust-lang#69232
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Zalathar authored Nov 29, 2024
2 parents 71ffb44 + 1e4817c commit 35b2ec5
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Showing 9 changed files with 75 additions and 12 deletions.
5 changes: 5 additions & 0 deletions compiler/rustc_hir_typeck/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,11 @@ hir_typeck_field_multiply_specified_in_initializer =
.label = used more than once
.previous_use_label = first use of `{$ident}`
hir_typeck_fn_item_to_variadic_function = can't pass a function item to a variadic function
.suggestion = use a function pointer instead
.help = a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
.note = for more information on function items, visit https://doc.rust-lang.org/reference/types/function-item.html
hir_typeck_fru_expr = this expression does not end in a comma...
hir_typeck_fru_expr2 = ... so this is interpreted as a `..` range expression, instead of functional record update syntax
hir_typeck_fru_note = this expression may have been misinterpreted as a `..` range expression
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12 changes: 12 additions & 0 deletions compiler/rustc_hir_typeck/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -797,3 +797,15 @@ pub(crate) struct PassToVariadicFunction<'a, 'tcx> {
#[note(hir_typeck_teach_help)]
pub(crate) teach: bool,
}

#[derive(Diagnostic)]
#[diag(hir_typeck_fn_item_to_variadic_function, code = E0617)]
#[help]
#[note]
pub(crate) struct PassFnItemToVariadicFunction {
#[primary_span]
pub span: Span,
#[suggestion(code = " as {replace}", applicability = "machine-applicable", style = "verbose")]
pub sugg_span: Span,
pub replace: String,
}
12 changes: 9 additions & 3 deletions compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
Original file line number Diff line number Diff line change
Expand Up @@ -472,9 +472,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
}
ty::FnDef(..) => {
let ptr_ty = Ty::new_fn_ptr(self.tcx, arg_ty.fn_sig(self.tcx));
let ptr_ty = self.resolve_vars_if_possible(ptr_ty);
variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
let fn_ptr = Ty::new_fn_ptr(self.tcx, arg_ty.fn_sig(self.tcx));
let fn_ptr = self.resolve_vars_if_possible(fn_ptr).to_string();

let fn_item_spa = arg.span;
tcx.sess.dcx().emit_err(errors::PassFnItemToVariadicFunction {
span: fn_item_spa,
sugg_span: fn_item_spa.shrink_to_hi(),
replace: fn_ptr,
});
}
_ => {}
}
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13 changes: 13 additions & 0 deletions tests/ui/c-variadic/fn-item-diagnostic-issue-69232.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
// https://github.com/rust-lang/rust/issues/69232

extern "C" {
fn foo(x: usize, ...);
}

fn test() -> u8 {
127
}

fn main() {
unsafe { foo(1, test) }; //~ ERROR can't pass a function item to a variadic function
}
16 changes: 16 additions & 0 deletions tests/ui/c-variadic/fn-item-diagnostic-issue-69232.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
error[E0617]: can't pass a function item to a variadic function
--> $DIR/fn-item-diagnostic-issue-69232.rs:12:21
|
LL | unsafe { foo(1, test) };
| ^^^^
|
= help: a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
= note: for more information on function items, visit https://doc.rust-lang.org/reference/types/function-item.html
help: use a function pointer instead
|
LL | unsafe { foo(1, test as fn() -> u8) };
| +++++++++++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0617`.
5 changes: 3 additions & 2 deletions tests/ui/c-variadic/issue-32201.rs
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,8 @@ fn bar(_: *const u8) {}
fn main() {
unsafe {
foo(0, bar);
//~^ ERROR can't pass `fn(*const u8) {bar}` to variadic function
//~| HELP cast the value to `fn(*const u8)`
//~^ ERROR can't pass a function item to a variadic function
//~| HELP a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
////~| HELP use a function pointer instead
}
}
11 changes: 9 additions & 2 deletions tests/ui/c-variadic/issue-32201.stderr
Original file line number Diff line number Diff line change
@@ -1,8 +1,15 @@
error[E0617]: can't pass `fn(*const u8) {bar}` to variadic function
error[E0617]: can't pass a function item to a variadic function
--> $DIR/issue-32201.rs:9:16
|
LL | foo(0, bar);
| ^^^ help: cast the value to `fn(*const u8)`: `bar as fn(*const u8)`
| ^^^
|
= help: a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
= note: for more information on function items, visit https://doc.rust-lang.org/reference/types/function-item.html
help: use a function pointer instead
|
LL | foo(0, bar as fn(*const u8));
| ++++++++++++++++

error: aborting due to 1 previous error

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5 changes: 3 additions & 2 deletions tests/ui/error-codes/E0617.rs
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,8 @@ fn main() {
//~^ ERROR can't pass `u16` to variadic function
//~| HELP cast the value to `c_uint`
printf(::std::ptr::null(), printf);
//~^ ERROR can't pass `unsafe extern "C" fn(*const i8, ...) {printf}` to variadic function
//~| HELP cast the value to `unsafe extern "C" fn(*const i8, ...)`
//~^ ERROR can't pass a function item to a variadic function
//~| HELP a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
//~| HELP use a function pointer instead
}
}
8 changes: 5 additions & 3 deletions tests/ui/error-codes/E0617.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -28,16 +28,18 @@ error[E0617]: can't pass `u16` to variadic function
LL | printf(::std::ptr::null(), 0u16);
| ^^^^ help: cast the value to `c_uint`: `0u16 as c_uint`

error[E0617]: can't pass `unsafe extern "C" fn(*const i8, ...) {printf}` to variadic function
error[E0617]: can't pass a function item to a variadic function
--> $DIR/E0617.rs:22:36
|
LL | printf(::std::ptr::null(), printf);
| ^^^^^^
|
help: cast the value to `unsafe extern "C" fn(*const i8, ...)`
= help: a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
= note: for more information on function items, visit https://doc.rust-lang.org/reference/types/function-item.html
help: use a function pointer instead
|
LL | printf(::std::ptr::null(), printf as unsafe extern "C" fn(*const i8, ...));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| +++++++++++++++++++++++++++++++++++++++

error: aborting due to 6 previous errors

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