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transpile: Pass expected type down to more expression kinds #1847

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2d3ef83
transpile: Use `convert_cast` when casting to expected type
Rua Jun 9, 2026
b360eed
transpile: Pass expected type for `AlignOf` and `PreferredAlignOf`
Rua Jun 9, 2026
0e49673
transpile: Pass expected type for `ImplicitValueInit`
Rua Jun 9, 2026
e60d182
transpile: Pass expected type for `ConstantExpr`
Rua Jun 10, 2026
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20 changes: 10 additions & 10 deletions c2rust-transpile/src/translator/functions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -452,16 +452,16 @@ impl<'c> Translation<'c> {

let args = self.convert_call_args(ctx.used(), args, arg_tys.as_deref(), is_variadic)?;

let mut call_expr = args.map(|args| mk().call_expr(func, args));
if let Some(expected_ty) = override_ty {
if call_expr_ty != expected_ty {
let ret_ty = self.convert_type(expected_ty.ctype)?;
call_expr = call_expr.map(|call| mk().cast_expr(call, ret_ty));
}
}

let res: TranslationResult<_> = Ok(call_expr);
res
let call_expr = args.map(|args| mk().call_expr(func, args));
self.convert_cast(
ctx,
call_expr_ty,
override_ty.unwrap_or(call_expr_ty),
call_expr,
None,
None,
None,
)
})?;

self.convert_side_effects_expr(
Expand Down
101 changes: 69 additions & 32 deletions c2rust-transpile/src/translator/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2872,33 +2872,34 @@ impl<'c> Translation<'c> {
pub fn compute_size_of_type(
&self,
ctx: ExprContext,
expected_type_id: Option<CQualTypeId>,
result_type_id: CQualTypeId,
type_id: CTypeId,
override_ty: Option<CQualTypeId>,
) -> TranslationResult<WithStmts<Box<Expr>>> {
if let CTypeKind::VariableArray(elts, len) = self.ast_context.resolve_type(type_id).kind {
let len = len.expect("Sizeof a VLA type with count expression omitted");

let elts = self.compute_size_of_type(ctx, elts, override_ty)?;
let elts = self.compute_size_of_type(ctx, expected_type_id, result_type_id, elts)?;
return elts.and_then_try(|lhs| {
let len = self.convert_expr(ctx.used().not_static(), len, override_ty)?;
let len = self.convert_expr(ctx.used().not_static(), len, expected_type_id)?;
Ok(len.map(|len| {
let rhs = cast_int(len, "usize", true);
mk().binary_expr(BinOp::Mul(Default::default()), lhs, rhs)
}))
});
}
let ty = self.convert_type(type_id)?;
let mut result = self.mk_size_of_ty_expr(ty);
// cast to expected ty if one is known
if let Some(expected_ty) = override_ty {
trace!(
"Converting result of sizeof to {:?}",
self.ast_context.resolve_type(expected_ty.ctype)
);
let result_ty = self.convert_type(expected_ty.ctype)?;
result = result.map(|x| x.map(|x| mk().cast_expr(x, result_ty)));
}
result
let result = self.mk_size_of_ty_expr(ty)?;

self.convert_cast(
ctx,
result_type_id,
expected_type_id.unwrap_or(result_type_id),
result,
None,
None,
None,
)
}

fn mk_size_of_ty_expr(&self, ty: Box<Type>) -> TranslationResult<WithStmts<Box<Expr>>> {
Expand All @@ -2916,6 +2917,9 @@ impl<'c> Translation<'c> {

pub fn compute_align_of_type(
&self,
ctx: ExprContext,
expected_type_id: Option<CQualTypeId>,
result_type_id: CQualTypeId,
mut type_id: CTypeId,
preferred: bool,
src_loc: &Option<SrcSpan>,
Expand Down Expand Up @@ -2952,7 +2956,15 @@ impl<'c> Translation<'c> {
path.push(mk().path_segment_with_args("align_of", mk().angle_bracketed_args(tys)));
}
let call = mk().call_expr(mk().abs_path_expr(path), vec![]);
Ok(WithStmts::new_val(call))
self.convert_cast(
ctx,
result_type_id,
expected_type_id.unwrap_or(result_type_id),
WithStmts::new_val(call),
None,
None,
None,
)
}

/// Convert multiple expressions (while collecting a context of statements) given either all or
Expand Down Expand Up @@ -3033,13 +3045,19 @@ impl<'c> Translation<'c> {
}),
ConvertVector(..) => Err(TranslationError::generic("convert vector not supported")),

UnaryType(_ty, kind, opt_expr, arg_ty) => {
UnaryType(result_type_id, kind, opt_expr, arg_ty) => {
let result = match kind {
CUnTypeOp::SizeOf => match opt_expr {
None => self.compute_size_of_type(ctx, arg_ty.ctype, override_ty)?,
None => self.compute_size_of_type(
ctx,
override_ty,
result_type_id,
arg_ty.ctype,
)?,
Some(_) => {
let inner = self.variable_array_base_type(arg_ty.ctype);
let inner_size = self.compute_size_of_type(ctx, inner, override_ty)?;
let inner_size =
self.compute_size_of_type(ctx, override_ty, result_type_id, inner)?;

if let Some(sz) = self.compute_size_of_expr(arg_ty.ctype) {
inner_size.map(|x| {
Expand All @@ -3051,12 +3069,22 @@ impl<'c> Translation<'c> {
}
}
},
CUnTypeOp::AlignOf => {
self.compute_align_of_type(arg_ty.ctype, false, src_loc)?
}
CUnTypeOp::PreferredAlignOf => {
self.compute_align_of_type(arg_ty.ctype, true, src_loc)?
}
CUnTypeOp::AlignOf => self.compute_align_of_type(
ctx,
override_ty,
result_type_id,
arg_ty.ctype,
false,
src_loc,
)?,
CUnTypeOp::PreferredAlignOf => self.compute_align_of_type(
ctx,
override_ty,
result_type_id,
arg_ty.ctype,
true,
src_loc,
)?,
};

Ok(result)
Expand All @@ -3066,7 +3094,7 @@ impl<'c> Translation<'c> {
if let Some(constant) = value {
self.convert_constant(constant).map(WithStmts::new_val)
} else {
self.convert_expr(ctx, child, Some(ty))
self.convert_expr(ctx, child, Some(override_ty.unwrap_or(ty)))
}
}

Expand Down Expand Up @@ -3190,14 +3218,21 @@ impl<'c> Translation<'c> {
val = mk().method_call_expr(val, "as_mut_ptr", vec![]);
}

// if the context wants a different type, add a cast
if let Some(expected_ty) = override_ty {
if lrvalue.is_rvalue() && expected_ty != qual_ty {
val = mk().cast_expr(val, self.convert_type(expected_ty.ctype)?);
}
let mut val = WithStmts::new_val(val).merge_unsafe(set_unsafe);

if lrvalue.is_rvalue() {
val = self.convert_cast(
ctx,
qual_ty,
override_ty.unwrap_or(qual_ty),
val,
None,
None,
None,
)?;
}

Ok(WithStmts::new_val(val).merge_unsafe(set_unsafe))
Ok(val)
}

OffsetOf(ty, ref kind) => match kind {
Expand Down Expand Up @@ -3480,7 +3515,9 @@ impl<'c> Translation<'c> {
self.convert_init_list(ctx, ty, ids, opt_union_field_id)
}

ImplicitValueInit(ty) => self.implicit_default_expr(ctx, ty.ctype),
ImplicitValueInit(ty) => {
self.implicit_default_expr(ctx, override_ty.unwrap_or(ty).ctype)
}

Predefined(_, val_id) => self.convert_expr(ctx, val_id, override_ty),

Expand Down
18 changes: 12 additions & 6 deletions c2rust-transpile/src/translator/pointers.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -342,13 +342,19 @@ impl<'c> Translation<'c> {

let mut val =
self.convert_pointer_offset(lhs, rhs, pointee_type_id.ctype, false, deref);
// if the context wants a different type, add a cast
if let Some(expected_ty) = override_ty {
if lrvalue.is_rvalue() && expected_ty != pointee_type_id {
let ty = self.convert_type(expected_ty.ctype)?;
val = val.map(|val| mk().cast_expr(val, ty));
}

if lrvalue.is_rvalue() {
val = self.convert_cast(
ctx,
pointee_type_id,
override_ty.unwrap_or(pointee_type_id),
val,
None,
None,
None,
)?;
}

Ok(val)
})
}
Expand Down
16 changes: 10 additions & 6 deletions c2rust-transpile/src/translator/structs_unions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1043,12 +1043,16 @@ impl<'a> Translation<'a> {
val = val.map(|v| mk().field_expr(v, field_name));
};

// if the context wants a different type, add a cast
if let Some(expected_ty) = override_ty {
if lrvalue.is_rvalue() && expected_ty != qual_ty {
let ty = self.convert_type(expected_ty.ctype)?;
val = val.map(|v| mk().cast_expr(v, ty));
}
if lrvalue.is_rvalue() {
val = self.convert_cast(
ctx,
qual_ty,
override_ty.unwrap_or(qual_ty),
val,
None,
None,
None,
)?;
}

Ok(val)
Expand Down
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@auto_type.c.2021.clang22.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ pub struct bar {
pub unsafe extern "C" fn foo() -> ::core::ffi::c_int {
let mut x: ::core::ffi::c_int = 42 as ::core::ffi::c_int;
let mut px: *mut ::core::ffi::c_int = &raw mut x;
let mut sx: usize = ::core::mem::size_of::<::core::ffi::c_int>() as usize;
let mut sx: usize = ::core::mem::size_of::<::core::ffi::c_int>();
let mut y: bar = bar {
x: x as ::core::ffi::c_int,
} as bar;
Expand Down
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@auto_type.c.2024.clang22.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ pub struct bar {
pub unsafe extern "C" fn foo() -> ::core::ffi::c_int {
let mut x: ::core::ffi::c_int = 42 as ::core::ffi::c_int;
let mut px: *mut ::core::ffi::c_int = &raw mut x;
let mut sx: usize = ::core::mem::size_of::<::core::ffi::c_int>() as usize;
let mut sx: usize = ::core::mem::size_of::<::core::ffi::c_int>();
let mut y: bar = bar {
x: x as ::core::ffi::c_int,
} as bar;
Expand Down
8 changes: 4 additions & 4 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@f128.c.2021.macos.clang15.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -34,12 +34,12 @@ pub unsafe extern "C" fn long_double_test() {
let mut f: ::core::ffi::c_float = one.to_f32().unwrap();
let mut cast_from_int: ::f128::f128 = ::f128::f128::new(i);
let mut cast_from_float: ::f128::f128 = ::f128::f128::new(f);
let mut is_inf: bool = if ::core::mem::size_of::<::f128::f128>() as usize
== ::core::mem::size_of::<::core::ffi::c_float>() as usize
let mut is_inf: bool = if ::core::mem::size_of::<::f128::f128>()
== ::core::mem::size_of::<::core::ffi::c_float>()
{
__inline_isinff(huge.to_f32().unwrap())
} else if ::core::mem::size_of::<::f128::f128>() as usize
== ::core::mem::size_of::<::core::ffi::c_double>() as usize
} else if ::core::mem::size_of::<::f128::f128>()
== ::core::mem::size_of::<::core::ffi::c_double>()
{
__inline_isinfd(huge.to_f64().unwrap())
} else {
Expand Down
8 changes: 4 additions & 4 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@f128.c.2024.macos.clang15.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -35,12 +35,12 @@ pub unsafe extern "C" fn long_double_test() {
let mut f: ::core::ffi::c_float = one.to_f32().unwrap();
let mut cast_from_int: ::f128::f128 = ::f128::f128::new(i);
let mut cast_from_float: ::f128::f128 = ::f128::f128::new(f);
let mut is_inf: bool = if ::core::mem::size_of::<::f128::f128>() as usize
== ::core::mem::size_of::<::core::ffi::c_float>() as usize
let mut is_inf: bool = if ::core::mem::size_of::<::f128::f128>()
== ::core::mem::size_of::<::core::ffi::c_float>()
{
__inline_isinff(huge.to_f32().unwrap())
} else if ::core::mem::size_of::<::f128::f128>() as usize
== ::core::mem::size_of::<::core::ffi::c_double>() as usize
} else if ::core::mem::size_of::<::f128::f128>()
== ::core::mem::size_of::<::core::ffi::c_double>()
{
__inline_isinfd(huge.to_f64().unwrap())
} else {
Expand Down
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2021.clang15.snap
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Expand Up @@ -348,7 +348,7 @@ pub static mut p: *const fn_ptrs = unsafe { &raw const fns };
pub const ZSTD_WINDOWLOG_MAX_32: ::core::ffi::c_int = 30 as ::core::ffi::c_int;
pub const ZSTD_WINDOWLOG_MAX_64: ::core::ffi::c_int = 31 as ::core::ffi::c_int;
pub const ZSTD_WINDOWLOG_MAX: ::core::ffi::c_int =
if ::core::mem::size_of::<zstd_platform_dependent_type>() as usize == 4 as usize {
if ::core::mem::size_of::<zstd_platform_dependent_type>() == 4 as usize {
ZSTD_WINDOWLOG_MAX_32
} else {
ZSTD_WINDOWLOG_MAX_64
Expand Down
6 changes: 3 additions & 3 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2021.linux.clang15.snap
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Expand Up @@ -37,10 +37,10 @@ pub unsafe extern "C" fn memcpy_str_literal(mut out: *mut ::core::ffi::c_char) {
memcpy(
out as *mut ::core::ffi::c_void,
POS.as_ptr() as *const ::core::ffi::c_void,
(::core::mem::size_of::<[::core::ffi::c_char; 3]>() as size_t)
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>() as size_t)
::core::mem::size_of::<[::core::ffi::c_char; 3]>()
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>())
.wrapping_sub(1 as size_t)
.wrapping_add(1 as size_t)
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>() as size_t),
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>()),
);
}
6 changes: 3 additions & 3 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2021.macos.clang15.snap
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Expand Up @@ -38,10 +38,10 @@ pub unsafe extern "C" fn memcpy_str_literal(mut out: *mut ::core::ffi::c_char) {
memcpy(
out as *mut ::core::ffi::c_void,
POS.as_ptr() as *const ::core::ffi::c_void,
(::core::mem::size_of::<[::core::ffi::c_char; 3]>() as size_t)
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>() as size_t)
::core::mem::size_of::<[::core::ffi::c_char; 3]>()
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>())
.wrapping_sub(1 as size_t)
.wrapping_add(1 as size_t)
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>() as size_t),
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>()),
);
}
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2024.clang15.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -348,7 +348,7 @@ pub static mut p: *const fn_ptrs = &raw const fns;
pub const ZSTD_WINDOWLOG_MAX_32: ::core::ffi::c_int = 30 as ::core::ffi::c_int;
pub const ZSTD_WINDOWLOG_MAX_64: ::core::ffi::c_int = 31 as ::core::ffi::c_int;
pub const ZSTD_WINDOWLOG_MAX: ::core::ffi::c_int =
if ::core::mem::size_of::<zstd_platform_dependent_type>() as usize == 4 as usize {
if ::core::mem::size_of::<zstd_platform_dependent_type>() == 4 as usize {
ZSTD_WINDOWLOG_MAX_32
} else {
ZSTD_WINDOWLOG_MAX_64
Expand Down
6 changes: 3 additions & 3 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2024.linux.clang15.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,10 @@ pub unsafe extern "C" fn memcpy_str_literal(mut out: *mut ::core::ffi::c_char) {
memcpy(
out as *mut ::core::ffi::c_void,
POS.as_ptr() as *const ::core::ffi::c_void,
(::core::mem::size_of::<[::core::ffi::c_char; 3]>() as size_t)
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>() as size_t)
::core::mem::size_of::<[::core::ffi::c_char; 3]>()
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>())
.wrapping_sub(1 as size_t)
.wrapping_add(1 as size_t)
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>() as size_t),
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>()),
);
}
6 changes: 3 additions & 3 deletions c2rust-transpile/tests/snapshots/snapshots__transpile@macros.c.2024.macos.clang15.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -39,10 +39,10 @@ pub unsafe extern "C" fn memcpy_str_literal(mut out: *mut ::core::ffi::c_char) {
memcpy(
out as *mut ::core::ffi::c_void,
POS.as_ptr() as *const ::core::ffi::c_void,
(::core::mem::size_of::<[::core::ffi::c_char; 3]>() as size_t)
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>() as size_t)
::core::mem::size_of::<[::core::ffi::c_char; 3]>()
.wrapping_div(::core::mem::size_of::<::core::ffi::c_char>())
.wrapping_sub(1 as size_t)
.wrapping_add(1 as size_t)
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>() as size_t),
.wrapping_mul(::core::mem::size_of::<::core::ffi::c_char>()),
);
}
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@wide_strings.c.2021.linux.clang22.snap
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Expand Up @@ -42,5 +42,5 @@ pub unsafe extern "C" fn func() {
let mut ptr: *const wchar_t =
const { ::core::mem::transmute::<[u8; 8], [::core::ffi::c_int; 2]>(*b"x\0\0\0\0\0\0\0") }
.as_ptr() as *const wchar_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t) as size_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t);
}
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@wide_strings.c.2021.macos.clang22.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -44,5 +44,5 @@ pub unsafe extern "C" fn func() {
let mut ptr: *const wchar_t =
const { ::core::mem::transmute::<[u8; 8], [::core::ffi::c_int; 2]>(*b"x\0\0\0\0\0\0\0") }
.as_ptr() as *const wchar_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t) as size_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t);
}
2 changes: 1 addition & 1 deletion c2rust-transpile/tests/snapshots/snapshots__transpile@wide_strings.c.2024.linux.clang22.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -42,5 +42,5 @@ pub unsafe extern "C" fn func() {
let mut ptr: *const wchar_t =
const { ::core::mem::transmute::<[u8; 8], [::core::ffi::c_int; 2]>(*b"x\0\0\0\0\0\0\0") }
.as_ptr() as *const wchar_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t) as size_t;
let mut len: size_t = wcslen(&raw mut array as *mut wchar_t);
}
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