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#![allow(clippy::similar_names)] // `expr` and `expn`
use crate::visitors::{for_each_expr, Descend};
use arrayvec::ArrayVec;
use rustc_ast::{FormatArgs, FormatArgument, FormatPlaceholder};
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::{self as hir, Expr, ExprKind, HirId, Node, QPath};
use rustc_lint::LateContext;
use rustc_span::def_id::DefId;
use rustc_span::hygiene::{self, MacroKind, SyntaxContext};
use rustc_span::{sym, BytePos, ExpnData, ExpnId, ExpnKind, Span, SpanData, Symbol};
use std::cell::OnceCell;
use std::ops::ControlFlow;
use std::rc::Rc;
use std::sync::atomic::{AtomicBool, Ordering};
const FORMAT_MACRO_DIAG_ITEMS: &[Symbol] = &[
sym::assert_eq_macro,
sym::assert_macro,
sym::assert_ne_macro,
sym::debug_assert_eq_macro,
sym::debug_assert_macro,
sym::debug_assert_ne_macro,
sym::eprint_macro,
sym::eprintln_macro,
sym::format_args_macro,
sym::format_macro,
sym::print_macro,
sym::println_macro,
sym::std_panic_macro,
sym::write_macro,
sym::writeln_macro,
];
/// Returns true if a given Macro `DefId` is a format macro (e.g. `println!`)
pub fn is_format_macro(cx: &LateContext<'_>, macro_def_id: DefId) -> bool {
if let Some(name) = cx.tcx.get_diagnostic_name(macro_def_id) {
FORMAT_MACRO_DIAG_ITEMS.contains(&name)
} else {
false
}
}
/// A macro call, like `vec![1, 2, 3]`.
///
/// Use `tcx.item_name(macro_call.def_id)` to get the macro name.
/// Even better is to check if it is a diagnostic item.
///
/// This structure is similar to `ExpnData` but it precludes desugaring expansions.
#[derive(Debug)]
pub struct MacroCall {
/// Macro `DefId`
pub def_id: DefId,
/// Kind of macro
pub kind: MacroKind,
/// The expansion produced by the macro call
pub expn: ExpnId,
/// Span of the macro call site
pub span: Span,
}
impl MacroCall {
pub fn is_local(&self) -> bool {
span_is_local(self.span)
}
}
/// Returns an iterator of expansions that created the given span
pub fn expn_backtrace(mut span: Span) -> impl Iterator<Item = (ExpnId, ExpnData)> {
std::iter::from_fn(move || {
let ctxt = span.ctxt();
if ctxt == SyntaxContext::root() {
return None;
}
let expn = ctxt.outer_expn();
let data = expn.expn_data();
span = data.call_site;
Some((expn, data))
})
}
/// Checks whether the span is from the root expansion or a locally defined macro
pub fn span_is_local(span: Span) -> bool {
!span.from_expansion() || expn_is_local(span.ctxt().outer_expn())
}
/// Checks whether the expansion is the root expansion or a locally defined macro
pub fn expn_is_local(expn: ExpnId) -> bool {
if expn == ExpnId::root() {
return true;
}
let data = expn.expn_data();
let backtrace = expn_backtrace(data.call_site);
std::iter::once((expn, data))
.chain(backtrace)
.find_map(|(_, data)| data.macro_def_id)
.map_or(true, DefId::is_local)
}
/// Returns an iterator of macro expansions that created the given span.
/// Note that desugaring expansions are skipped.
pub fn macro_backtrace(span: Span) -> impl Iterator<Item = MacroCall> {
expn_backtrace(span).filter_map(|(expn, data)| match data {
ExpnData {
kind: ExpnKind::Macro(kind, _),
macro_def_id: Some(def_id),
call_site: span,
..
} => Some(MacroCall {
def_id,
kind,
expn,
span,
}),
_ => None,
})
}
/// If the macro backtrace of `span` has a macro call at the root expansion
/// (i.e. not a nested macro call), returns `Some` with the `MacroCall`
pub fn root_macro_call(span: Span) -> Option<MacroCall> {
macro_backtrace(span).last()
}
/// Like [`root_macro_call`], but only returns `Some` if `node` is the "first node"
/// produced by the macro call, as in [`first_node_in_macro`].
pub fn root_macro_call_first_node(cx: &LateContext<'_>, node: &impl HirNode) -> Option<MacroCall> {
if first_node_in_macro(cx, node) != Some(ExpnId::root()) {
return None;
}
root_macro_call(node.span())
}
/// Like [`macro_backtrace`], but only returns macro calls where `node` is the "first node" of the
/// macro call, as in [`first_node_in_macro`].
pub fn first_node_macro_backtrace(cx: &LateContext<'_>, node: &impl HirNode) -> impl Iterator<Item = MacroCall> {
let span = node.span();
first_node_in_macro(cx, node)
.into_iter()
.flat_map(move |expn| macro_backtrace(span).take_while(move |macro_call| macro_call.expn != expn))
}
/// If `node` is the "first node" in a macro expansion, returns `Some` with the `ExpnId` of the
/// macro call site (i.e. the parent of the macro expansion). This generally means that `node`
/// is the outermost node of an entire macro expansion, but there are some caveats noted below.
/// This is useful for finding macro calls while visiting the HIR without processing the macro call
/// at every node within its expansion.
///
/// If you already have immediate access to the parent node, it is simpler to
/// just check the context of that span directly (e.g. `parent.span.from_expansion()`).
///
/// If a macro call is in statement position, it expands to one or more statements.
/// In that case, each statement *and* their immediate descendants will all yield `Some`
/// with the `ExpnId` of the containing block.
///
/// A node may be the "first node" of multiple macro calls in a macro backtrace.
/// The expansion of the outermost macro call site is returned in such cases.
pub fn first_node_in_macro(cx: &LateContext<'_>, node: &impl HirNode) -> Option<ExpnId> {
// get the macro expansion or return `None` if not found
// `macro_backtrace` importantly ignores desugaring expansions
let expn = macro_backtrace(node.span()).next()?.expn;
// get the parent node, possibly skipping over a statement
// if the parent is not found, it is sensible to return `Some(root)`
let hir = cx.tcx.hir();
let mut parent_iter = hir.parent_iter(node.hir_id());
let (parent_id, _) = match parent_iter.next() {
None => return Some(ExpnId::root()),
Some((_, Node::Stmt(_))) => match parent_iter.next() {
None => return Some(ExpnId::root()),
Some(next) => next,
},
Some(next) => next,
};
// get the macro expansion of the parent node
let parent_span = hir.span(parent_id);
let Some(parent_macro_call) = macro_backtrace(parent_span).next() else {
// the parent node is not in a macro
return Some(ExpnId::root());
};
if parent_macro_call.expn.is_descendant_of(expn) {
// `node` is input to a macro call
return None;
}
Some(parent_macro_call.expn)
}
/* Specific Macro Utils */
/// Is `def_id` of `std::panic`, `core::panic` or any inner implementation macros
pub fn is_panic(cx: &LateContext<'_>, def_id: DefId) -> bool {
let Some(name) = cx.tcx.get_diagnostic_name(def_id) else {
return false;
};
matches!(
name,
sym::core_panic_macro
| sym::std_panic_macro
| sym::core_panic_2015_macro
| sym::std_panic_2015_macro
| sym::core_panic_2021_macro
)
}
/// Is `def_id` of `assert!` or `debug_assert!`
pub fn is_assert_macro(cx: &LateContext<'_>, def_id: DefId) -> bool {
let Some(name) = cx.tcx.get_diagnostic_name(def_id) else {
return false;
};
matches!(name, sym::assert_macro | sym::debug_assert_macro)
}
#[derive(Debug)]
pub enum PanicExpn<'a> {
/// No arguments - `panic!()`
Empty,
/// A string literal or any `&str` - `panic!("message")` or `panic!(message)`
Str(&'a Expr<'a>),
/// A single argument that implements `Display` - `panic!("{}", object)`
Display(&'a Expr<'a>),
/// Anything else - `panic!("error {}: {}", a, b)`
Format(&'a Expr<'a>),
}
impl<'a> PanicExpn<'a> {
pub fn parse(expr: &'a Expr<'a>) -> Option<Self> {
let ExprKind::Call(callee, args) = &expr.kind else {
return None;
};
let ExprKind::Path(QPath::Resolved(_, path)) = &callee.kind else {
return None;
};
let name = path.segments.last().unwrap().ident.as_str();
// This has no argument
if name == "panic_cold_explicit" {
return Some(Self::Empty);
};
let [arg, rest @ ..] = args else {
return None;
};
let result = match name {
"panic" if arg.span.ctxt() == expr.span.ctxt() => Self::Empty,
"panic" | "panic_str" => Self::Str(arg),
"panic_display" | "panic_cold_display" => {
let ExprKind::AddrOf(_, _, e) = &arg.kind else {
return None;
};
Self::Display(e)
},
"panic_fmt" => Self::Format(arg),
// Since Rust 1.52, `assert_{eq,ne}` macros expand to use:
// `core::panicking::assert_failed(.., left_val, right_val, None | Some(format_args!(..)));`
"assert_failed" => {
// It should have 4 arguments in total (we already matched with the first argument,
// so we're just checking for 3)
if rest.len() != 3 {
return None;
}
// `msg_arg` is either `None` (no custom message) or `Some(format_args!(..))` (custom message)
let msg_arg = &rest[2];
match msg_arg.kind {
ExprKind::Call(_, [fmt_arg]) => Self::Format(fmt_arg),
_ => Self::Empty,
}
},
_ => return None,
};
Some(result)
}
}
/// Finds the arguments of an `assert!` or `debug_assert!` macro call within the macro expansion
pub fn find_assert_args<'a>(
cx: &LateContext<'_>,
expr: &'a Expr<'a>,
expn: ExpnId,
) -> Option<(&'a Expr<'a>, PanicExpn<'a>)> {
find_assert_args_inner(cx, expr, expn).map(|([e], mut p)| {
// `assert!(..)` expands to `core::panicking::panic("assertion failed: ...")` (which we map to
// `PanicExpn::Str(..)`) and `assert!(.., "..")` expands to
// `core::panicking::panic_fmt(format_args!(".."))` (which we map to `PanicExpn::Format(..)`).
// So even we got `PanicExpn::Str(..)` that means there is no custom message provided
if let PanicExpn::Str(_) = p {
p = PanicExpn::Empty;
}
(e, p)
})
}
/// Finds the arguments of an `assert_eq!` or `debug_assert_eq!` macro call within the macro
/// expansion
pub fn find_assert_eq_args<'a>(
cx: &LateContext<'_>,
expr: &'a Expr<'a>,
expn: ExpnId,
) -> Option<(&'a Expr<'a>, &'a Expr<'a>, PanicExpn<'a>)> {
find_assert_args_inner(cx, expr, expn).map(|([a, b], p)| (a, b, p))
}
fn find_assert_args_inner<'a, const N: usize>(
cx: &LateContext<'_>,
expr: &'a Expr<'a>,
expn: ExpnId,
) -> Option<([&'a Expr<'a>; N], PanicExpn<'a>)> {
let macro_id = expn.expn_data().macro_def_id?;
let (expr, expn) = match cx.tcx.item_name(macro_id).as_str().strip_prefix("debug_") {
None => (expr, expn),
Some(inner_name) => find_assert_within_debug_assert(cx, expr, expn, Symbol::intern(inner_name))?,
};
let mut args = ArrayVec::new();
let panic_expn = for_each_expr(expr, |e| {
if args.is_full() {
match PanicExpn::parse(e) {
Some(expn) => ControlFlow::Break(expn),
None => ControlFlow::Continue(Descend::Yes),
}
} else if is_assert_arg(cx, e, expn) {
args.push(e);
ControlFlow::Continue(Descend::No)
} else {
ControlFlow::Continue(Descend::Yes)
}
});
let args = args.into_inner().ok()?;
// if no `panic!(..)` is found, use `PanicExpn::Empty`
// to indicate that the default assertion message is used
let panic_expn = panic_expn.unwrap_or(PanicExpn::Empty);
Some((args, panic_expn))
}
fn find_assert_within_debug_assert<'a>(
cx: &LateContext<'_>,
expr: &'a Expr<'a>,
expn: ExpnId,
assert_name: Symbol,
) -> Option<(&'a Expr<'a>, ExpnId)> {
for_each_expr(expr, |e| {
if !e.span.from_expansion() {
return ControlFlow::Continue(Descend::No);
}
let e_expn = e.span.ctxt().outer_expn();
if e_expn == expn {
ControlFlow::Continue(Descend::Yes)
} else if e_expn.expn_data().macro_def_id.map(|id| cx.tcx.item_name(id)) == Some(assert_name) {
ControlFlow::Break((e, e_expn))
} else {
ControlFlow::Continue(Descend::No)
}
})
}
fn is_assert_arg(cx: &LateContext<'_>, expr: &Expr<'_>, assert_expn: ExpnId) -> bool {
if !expr.span.from_expansion() {
return true;
}
let result = macro_backtrace(expr.span).try_for_each(|macro_call| {
if macro_call.expn == assert_expn {
ControlFlow::Break(false)
} else {
match cx.tcx.item_name(macro_call.def_id) {
// `cfg!(debug_assertions)` in `debug_assert!`
sym::cfg => ControlFlow::Continue(()),
// assert!(other_macro!(..))
_ => ControlFlow::Break(true),
}
}
});
match result {
ControlFlow::Break(is_assert_arg) => is_assert_arg,
ControlFlow::Continue(()) => true,
}
}
thread_local! {
/// We preserve the [`FormatArgs`] structs from the early pass for use in the late pass to be
/// able to access the many features of a [`LateContext`].
///
/// A thread local is used because [`FormatArgs`] is `!Send` and `!Sync`, we are making an
/// assumption that the early pass that populates the map and the later late passes will all be
/// running on the same thread.
#[doc(hidden)]
pub static AST_FORMAT_ARGS: OnceCell<FxHashMap<Span, Rc<FormatArgs>>> = {
static CALLED: AtomicBool = AtomicBool::new(false);
debug_assert!(
!CALLED.swap(true, Ordering::SeqCst),
"incorrect assumption: `AST_FORMAT_ARGS` should only be accessed by a single thread",
);
OnceCell::new()
};
}
/// Returns an AST [`FormatArgs`] node if a `format_args` expansion is found as a descendant of
/// `expn_id`
pub fn find_format_args(cx: &LateContext<'_>, start: &Expr<'_>, expn_id: ExpnId) -> Option<Rc<FormatArgs>> {
let format_args_expr = for_each_expr(start, |expr| {
let ctxt = expr.span.ctxt();
if ctxt.outer_expn().is_descendant_of(expn_id) {
if macro_backtrace(expr.span)
.map(|macro_call| cx.tcx.item_name(macro_call.def_id))
.any(|name| matches!(name, sym::const_format_args | sym::format_args | sym::format_args_nl))
{
ControlFlow::Break(expr)
} else {
ControlFlow::Continue(Descend::Yes)
}
} else {
ControlFlow::Continue(Descend::No)
}
})?;
AST_FORMAT_ARGS.with(|ast_format_args| {
ast_format_args
.get()?
.get(&format_args_expr.span.with_parent(None))
.map(Rc::clone)
})
}
/// Attempt to find the [`rustc_hir::Expr`] that corresponds to the [`FormatArgument`]'s value, if
/// it cannot be found it will return the [`rustc_ast::Expr`].
pub fn find_format_arg_expr<'hir, 'ast>(
start: &'hir Expr<'hir>,
target: &'ast FormatArgument,
) -> Result<&'hir rustc_hir::Expr<'hir>, &'ast rustc_ast::Expr> {
let SpanData {
lo,
hi,
ctxt,
parent: _,
} = target.expr.span.data();
for_each_expr(start, |expr| {
// When incremental compilation is enabled spans gain a parent during AST to HIR lowering,
// since we're comparing an AST span to a HIR one we need to ignore the parent field
let data = expr.span.data();
if data.lo == lo && data.hi == hi && data.ctxt == ctxt {
ControlFlow::Break(expr)
} else {
ControlFlow::Continue(())
}
})
.ok_or(&target.expr)
}
/// Span of the `:` and format specifiers
///
/// ```ignore
/// format!("{:.}"), format!("{foo:.}")
/// ^^ ^^
/// ```
pub fn format_placeholder_format_span(placeholder: &FormatPlaceholder) -> Option<Span> {
let base = placeholder.span?.data();
// `base.hi` is `{...}|`, subtract 1 byte (the length of '}') so that it points before the closing
// brace `{...|}`
Some(Span::new(
placeholder.argument.span?.hi(),
base.hi - BytePos(1),
base.ctxt,
base.parent,
))
}
/// Span covering the format string and values
///
/// ```ignore
/// format("{}.{}", 10, 11)
/// // ^^^^^^^^^^^^^^^
/// ```
pub fn format_args_inputs_span(format_args: &FormatArgs) -> Span {
match format_args.arguments.explicit_args() {
[] => format_args.span,
[.., last] => format_args
.span
.to(hygiene::walk_chain(last.expr.span, format_args.span.ctxt())),
}
}
/// Returns the [`Span`] of the value at `index` extended to the previous comma, e.g. for the value
/// `10`
///
/// ```ignore
/// format("{}.{}", 10, 11)
/// // ^^^^
/// ```
pub fn format_arg_removal_span(format_args: &FormatArgs, index: usize) -> Option<Span> {
let ctxt = format_args.span.ctxt();
let current = hygiene::walk_chain(format_args.arguments.by_index(index)?.expr.span, ctxt);
let prev = if index == 0 {
format_args.span
} else {
hygiene::walk_chain(format_args.arguments.by_index(index - 1)?.expr.span, ctxt)
};
Some(current.with_lo(prev.hi()))
}
/// Where a format parameter is being used in the format string
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum FormatParamUsage {
/// Appears as an argument, e.g. `format!("{}", foo)`
Argument,
/// Appears as a width, e.g. `format!("{:width$}", foo, width = 1)`
Width,
/// Appears as a precision, e.g. `format!("{:.precision$}", foo, precision = 1)`
Precision,
}
/// A node with a `HirId` and a `Span`
pub trait HirNode {
fn hir_id(&self) -> HirId;
fn span(&self) -> Span;
}
macro_rules! impl_hir_node {
($($t:ident),*) => {
$(impl HirNode for hir::$t<'_> {
fn hir_id(&self) -> HirId {
self.hir_id
}
fn span(&self) -> Span {
self.span
}
})*
};
}
impl_hir_node!(Expr, Pat);
impl HirNode for hir::Item<'_> {
fn hir_id(&self) -> HirId {
self.hir_id()
}
fn span(&self) -> Span {
self.span
}
}