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transpile: Make unwrapping Paren explicit #1825

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9706437
transpile: Rename `resolve_parens` to `unwrap_parens`
Rua May 23, 2026
03512f8
transpile: Add `index_unwrap_parens` function
Rua May 23, 2026
55063c8
transpile: Replace all `CExprId` indexing with `index_unwrap_parens`
Rua May 23, 2026
43c1525
transpile: Do not unwrap `Paren` when indexing with `CExprId`
Rua May 23, 2026
9351ea9
transpile: Use plain `CExprId` indexing where `Paren` is explicitly h…
Rua May 23, 2026
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60 changes: 35 additions & 25 deletions c2rust-transpile/src/c_ast/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -359,7 +359,7 @@ impl TypedAstContext {
use SomeId::*;
match id {
Stmt(id) => self.index(id).loc,
Expr(id) => self.index(id).loc,
Expr(id) => self.index_unwrap_parens(id).loc,
Decl(id) => self.index(id).loc,
Type(id) => self.index(id).loc,
}
Expand Down Expand Up @@ -487,7 +487,7 @@ impl TypedAstContext {

pub fn is_null_expr(&self, expr_id: CExprId) -> bool {
use CExprKind::*;
match self[expr_id].kind {
match self.index_unwrap_parens(expr_id).kind {
ExplicitCast(_, _, CastKind::NullToPointer, _, _)
| ImplicitCast(_, _, CastKind::NullToPointer, _, _) => true,

Expand Down Expand Up @@ -673,17 +673,30 @@ impl TypedAstContext {
}

/// Returns the expression inside any number of nested parentheses.
pub fn resolve_parens(&self, mut expr_id: CExprId) -> CExprId {
while let CExprKind::Paren(_, subexpr) = self.index(expr_id).kind {
pub fn unwrap_parens(&self, mut expr_id: CExprId) -> CExprId {
while let CExprKind::Paren(_, subexpr) = self[expr_id].kind {
expr_id = subexpr;
}

expr_id
}

/// Same as the index operator, but unwraps `Paren` expressions.
pub fn index_unwrap_parens(&self, expr_id: CExprId) -> &CExpr {
static BADEXPR: CExpr = Located {
loc: None,
kind: CExprKind::BadExpr,
};
self.c_exprs
.get(&self.unwrap_parens(expr_id))
.unwrap_or(&BADEXPR)
}

/// Returns the expression inside an `__extension__` operator.
pub fn resolve_extension(&self, expr_id: CExprId) -> CExprId {
if let CExprKind::Unary(_, CUnOp::Extension, subexpr, _) = self.index(expr_id).kind {
if let CExprKind::Unary(_, CUnOp::Extension, subexpr, _) =
self.index_unwrap_parens(expr_id).kind
{
subexpr
} else {
expr_id
Expand All @@ -692,9 +705,9 @@ impl TypedAstContext {

/// Unwraps a predefined expression, if there is one.
pub fn unwrap_predefined_ident(&self, mut expr_id: CExprId) -> CExprId {
expr_id = self.resolve_extension(self.resolve_parens(expr_id));
expr_id = self.resolve_extension(self.unwrap_parens(expr_id));

if let CExprKind::Predefined(_, subexpr) = self.index(expr_id).kind {
if let CExprKind::Predefined(_, subexpr) = self.index_unwrap_parens(expr_id).kind {
subexpr
} else {
expr_id
Expand All @@ -705,7 +718,7 @@ impl TypedAstContext {
pub fn unwrap_cast_expr(&self, mut expr_id: CExprId) -> CExprId {
while let CExprKind::Paren(_, subexpr)
| CExprKind::ImplicitCast(_, subexpr, _, _, _)
| CExprKind::ExplicitCast(_, subexpr, _, _, _) = self.index(expr_id).kind
| CExprKind::ExplicitCast(_, subexpr, _, _, _) = self[expr_id].kind
{
expr_id = subexpr;
}
Expand All @@ -715,7 +728,9 @@ impl TypedAstContext {

/// Unwraps the underlying expression beneath any implicit casts.
pub fn unwrap_implicit_cast_expr(&self, mut expr_id: CExprId) -> CExprId {
while let CExprKind::ImplicitCast(_, subexpr, _, _, _) = self.index(expr_id).kind {
while let CExprKind::ImplicitCast(_, subexpr, _, _, _) =
self.index_unwrap_parens(expr_id).kind
{
expr_id = subexpr;
}

Expand All @@ -725,7 +740,7 @@ impl TypedAstContext {
/// Resolve true expression type, iterating through any casts and variable
/// references.
pub fn resolve_expr_type_id(&self, expr_id: CExprId) -> Option<(CExprId, CTypeId)> {
let expr = &self.index(expr_id).kind;
let expr = &self[expr_id].kind;
let mut ty = expr.get_type();
use CExprKind::*;
match expr {
Expand Down Expand Up @@ -804,9 +819,10 @@ impl TypedAstContext {
/// Looks for ImplicitCast(FunctionToPointerDecay, DeclRef(function_decl))
pub fn fn_declref_decl(&self, func_expr: CExprId) -> Option<&CDeclKind> {
use CastKind::FunctionToPointerDecay;
if let CExprKind::ImplicitCast(_, fexp, FunctionToPointerDecay, _, _) = self[func_expr].kind
if let CExprKind::ImplicitCast(_, fexp, FunctionToPointerDecay, _, _) =
self.index_unwrap_parens(func_expr).kind
{
if let CExprKind::DeclRef(_ty, decl_id, _rv) = &self[fexp].kind {
if let CExprKind::DeclRef(_ty, decl_id, _rv) = &self.index_unwrap_parens(fexp).kind {
let decl = &self.index(*decl_id).kind;
assert!(matches!(decl, CDeclKind::Function { .. }));
return Some(decl);
Expand Down Expand Up @@ -868,7 +884,7 @@ impl TypedAstContext {
pub fn is_expr_pure(&self, expr: CExprId) -> bool {
use CExprKind::*;
let pure = |expr| self.is_expr_pure(expr);
match self.index(expr).kind {
match self[expr].kind {
BadExpr |
ShuffleVector(..) |
ConvertVector(..) |
Expand Down Expand Up @@ -912,12 +928,12 @@ impl TypedAstContext {
/// Pessimistically try to check if an expression doesn't return.
/// If it does, or we can't tell that it doesn't, return `false`.
pub fn expr_diverges(&self, expr_id: CExprId) -> bool {
let func_id = match self.index(expr_id).kind {
let func_id = match self.index_unwrap_parens(expr_id).kind {
CExprKind::Call(_, func_id, _) => func_id,
_ => return false,
};

let type_id = match self[func_id].kind.get_type() {
let type_id = match self.index_unwrap_parens(func_id).kind.get_type() {
None => return false,
Some(t) => t,
};
Expand Down Expand Up @@ -1174,7 +1190,7 @@ impl TypedAstContext {
}

Expr(expr_id) => {
let expr = self.index(expr_id);
let expr = self.index_unwrap_parens(expr_id);
if let Some(macs) = self.macro_invocations.get(&expr_id) {
for mac_id in macs {
if wanted.insert(*mac_id) {
Expand Down Expand Up @@ -1254,7 +1270,7 @@ impl TypedAstContext {
_ => return,
};

let new_ty = match self.ast_context.c_exprs[&e].kind {
let new_ty = match self.ast_context[e].kind {
CExprKind::Conditional(_ty, _cond, lhs, rhs) => {
let lhs_type_id =
self.ast_context.c_exprs[&lhs].kind.get_qual_type().unwrap();
Expand Down Expand Up @@ -1502,21 +1518,15 @@ impl Index<CTypeId> for TypedAstContext {

impl Index<CExprId> for TypedAstContext {
type Output = CExpr;

fn index(&self, index: CExprId) -> &CExpr {
static BADEXPR: CExpr = Located {
loc: None,
kind: CExprKind::BadExpr,
};
match self.c_exprs.get(&index) {
None => &BADEXPR, // panic!("Could not find {:?} in TypedAstContext", index),
Some(e) => {
// Transparently index through Paren expressions
if let CExprKind::Paren(_, subexpr) = e.kind {
self.index(subexpr)
} else {
e
}
}
Some(e) => e,
}
}
}
Expand Down
32 changes: 25 additions & 7 deletions c2rust-transpile/src/cfg/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1453,7 +1453,11 @@ impl CfgBuilder {
.discard_unsafe();
wip.extend(stmts);

let cond_val = translator.ast_context[scrutinee].kind.get_bool();
let cond_val = translator
.ast_context
.index_unwrap_parens(scrutinee)
.kind
.get_bool();
self.add_wip_block(
wip,
match cond_val {
Expand Down Expand Up @@ -1520,7 +1524,11 @@ impl CfgBuilder {
let (stmts, val) = translator
.convert_condition(ctx, true, condition)?
.discard_unsafe();
let cond_val = translator.ast_context[condition].kind.get_bool();
let cond_val = translator
.ast_context
.index_unwrap_parens(condition)
.kind
.get_bool();
let mut cond_wip = self.new_wip_block(cond_entry.clone());
cond_wip.extend(stmts);

Expand Down Expand Up @@ -1595,7 +1603,11 @@ impl CfgBuilder {
let (stmts, val) = translator
.convert_condition(ctx, true, condition)?
.discard_unsafe();
let cond_val = translator.ast_context[condition].kind.get_bool();
let cond_val = translator
.ast_context
.index_unwrap_parens(condition)
.kind
.get_bool();
let mut cond_wip = self.new_wip_block(cond_entry);
cond_wip.extend(stmts);
self.add_wip_block(
Expand Down Expand Up @@ -1646,7 +1658,11 @@ impl CfgBuilder {
let (stmts, val) = translator
.convert_condition(ctx, true, cond)?
.discard_unsafe();
let cond_val = translator.ast_context[cond].kind.get_bool();
let cond_val = translator
.ast_context
.index_unwrap_parens(cond)
.kind
.get_bool();
let mut cond_wip = slf.new_wip_block(cond_entry.clone());
cond_wip.extend(stmts);
slf.add_wip_block(
Expand Down Expand Up @@ -1772,9 +1788,11 @@ impl CfgBuilder {
// We simply inline the common statement at this point rather
// than to try and create new control-flow blocks.
let blk_or_wip = if let CExprKind::Unary(_, CUnOp::Extension, sube, _) =
translator.ast_context[expr].kind
translator.ast_context.index_unwrap_parens(expr).kind
{
if let CExprKind::Statements(_, stmtid) = translator.ast_context[sube].kind {
if let CExprKind::Statements(_, stmtid) =
translator.ast_context.index_unwrap_parens(sube).kind
{
let comp_entry = self.fresh_label();
self.add_wip_block(wip, Jump(comp_entry.clone()));
let next_lbl = self.convert_stmt_help(
Expand Down Expand Up @@ -1858,7 +1876,7 @@ impl CfgBuilder {

// Case
let resolved = translator.ast_context.unwrap_cast_expr(case_expr);
let branch = match translator.ast_context.index(resolved).kind {
let branch = match translator.ast_context.index_unwrap_parens(resolved).kind {
CExprKind::Literal(..) | CExprKind::ConstantExpr(_, _, Some(_)) => {
match translator
.convert_expr(ctx.used(), resolved, None)?
Expand Down
16 changes: 11 additions & 5 deletions c2rust-transpile/src/translator/atomics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -98,14 +98,14 @@ impl<'c> Translation<'c> {

fn convert_constant_bool(&self, expr: CExprId) -> Option<bool> {
let val = self.ast_context.unwrap_cast_expr(expr);
match self.ast_context.index(val).kind {
match self.ast_context.index_unwrap_parens(val).kind {
CExprKind::Literal(_, CLiteral::Integer(i, _)) => Some(i != 0),
_ => None,
}
}

fn convert_memordering(&self, expr: CExprId) -> Option<Ordering> {
let memorder = &self.ast_context[expr];
let memorder = &self.ast_context.index_unwrap_parens(expr);
let i = match memorder.kind {
CExprKind::Literal(_, CLiteral::Integer(i, _)) => Some(i),
CExprKind::DeclRef(_, decl_id, LRValue::RValue) => {
Expand Down Expand Up @@ -295,8 +295,12 @@ impl<'c> Translation<'c> {
}
.ok_or_else(|| {
format_translation_err!(
self.ast_context
.display_loc(&self.ast_context[order_fail_id.unwrap()].loc),
self.ast_context.display_loc(
&self
.ast_context
.index_unwrap_parens(order_fail_id.unwrap())
.loc
),
"Invalid failure memory ordering",
)
})?;
Expand Down Expand Up @@ -337,7 +341,9 @@ impl<'c> Translation<'c> {
let order = static_order(order);
let val =
val1.expect("__atomic arithmetic operations must have a val argument");
let val_type_id = self.ast_context[val1_id.unwrap()]
let val_type_id = self
.ast_context
.index_unwrap_parens(val1_id.unwrap())
.kind
.get_qual_type()
.ok_or_else(|| format_err!("bad val1 type"))?;
Expand Down
10 changes: 7 additions & 3 deletions c2rust-transpile/src/translator/builtins.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ impl<'c> Translation<'c> {
fexp: CExprId,
args: &[CExprId],
) -> TranslationResult<WithStmts<Box<Expr>>> {
let expr = &self.ast_context[fexp];
let expr = &self.ast_context.index_unwrap_parens(fexp);
let src_loc = &expr.loc;
let decl_id = match expr.kind {
CExprKind::DeclRef(_, decl_id, _) => decl_id,
Expand Down Expand Up @@ -590,7 +590,9 @@ impl<'c> Translation<'c> {
if let Some(atomic_op) = CAtomicBinOp::from_sync_builtin_fn(builtin_name) {
let arg0 = self.convert_expr(ctx.used(), args[0], None)?;
let arg1 = self.convert_expr(ctx.used(), args[1], None)?;
let arg1_type_id = self.ast_context[args[1]]
let arg1_type_id = self
.ast_context
.index_unwrap_parens(args[1])
.kind
.get_qual_type()
.ok_or_else(|| format_err!("bad arg1 type"))?;
Expand All @@ -611,7 +613,9 @@ impl<'c> Translation<'c> {
}

fn import_num_traits(&self, arg_id: CExprId) -> TranslationResult<()> {
let arg_type_id = self.ast_context[arg_id]
let arg_type_id = self
.ast_context
.index_unwrap_parens(arg_id)
.kind
.get_qual_type()
.ok_or_else(|| format_err!("bad arg type"))?;
Expand Down
4 changes: 2 additions & 2 deletions c2rust-transpile/src/translator/enums.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,7 @@ impl<'c> Translation<'c> {
val: Box<Expr>,
) -> TranslationResult<Box<Expr>> {
if let Some(expr) = expr {
match self.ast_context[expr].kind {
match self.ast_context.index_unwrap_parens(expr).kind {
// This is the case of finding a variable which is an `EnumConstant` of the same
// enum we are casting to. Here, we can just remove the extraneous cast instead of
// generating a new one.
Expand All @@ -112,7 +112,7 @@ impl<'c> Translation<'c> {

CExprKind::Unary(_, CUnOp::Negate, subexpr_id, _) => {
if let &CExprKind::Literal(_, CLiteral::Integer(i, _)) =
&self.ast_context[subexpr_id].kind
&self.ast_context.index_unwrap_parens(subexpr_id).kind
{
return Ok(self.enum_for_i64(enum_type_id, -(i as i64)));
}
Expand Down
15 changes: 10 additions & 5 deletions c2rust-transpile/src/translator/functions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -365,7 +365,8 @@ impl<'c> Translation<'c> {
let fn_ty = self
.ast_context
.get_pointee_qual_type(
self.ast_context[func]
self.ast_context
.index_unwrap_parens(func)
.kind
.get_type()
.ok_or_else(|| format_err!("Invalid callee expression {:?}", func))?,
Expand All @@ -384,12 +385,12 @@ impl<'c> Translation<'c> {
None
};

let func = match self.ast_context[func].kind {
let func = match self.ast_context.index_unwrap_parens(func).kind {
// Direct function call
CExprKind::ImplicitCast(_, fexp, CastKind::FunctionToPointerDecay, _, _)
// Only a direct function call with pointer decay if the
// callee is a declref
if matches!(self.ast_context[fexp].kind, CExprKind::DeclRef(..)) =>
if matches!(self.ast_context.index_unwrap_parens(fexp).kind, CExprKind::DeclRef(..)) =>
{
self.convert_expr(ctx.used(), fexp, None)?
}
Expand Down Expand Up @@ -507,8 +508,12 @@ impl<'c> Translation<'c> {
) -> TranslationResult<WithStmts<Box<Expr>>> {
let mut val;

if (self.ast_context.index(expr_id).kind.get_qual_type())
.map_or(false, |qtype| self.ast_context.is_va_list(qtype.ctype))
if (self
.ast_context
.index_unwrap_parens(expr_id)
.kind
.get_qual_type())
.map_or(false, |qtype| self.ast_context.is_va_list(qtype.ctype))
{
// No `override_ty` to avoid unwanted casting.
val = self.convert_expr(ctx, expr_id, None)?;
Expand Down
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