// This test does the following for every file in the rust-lang/rust repo:
//
// 1. Parse the file using syn into a syn::File.
// 2. Extract every syn::Expr from the file.
// 3. Print each expr to a string of source code.
// 4. Parse the source code using librustc_parse into a rustc_ast::Expr.
// 5. For both the syn::Expr and rustc_ast::Expr, crawl the syntax tree to
// insert parentheses surrounding every subexpression.
// 6. Serialize the fully parenthesized syn::Expr to a string of source code.
// 7. Parse the fully parenthesized source code using librustc_parse.
// 8. Compare the rustc_ast::Expr resulting from parenthesizing using rustc data
// structures vs syn data structures, ignoring spans. If they agree, rustc's
// parser and syn's parser have identical handling of expression precedence.
#![cfg(not(syn_disable_nightly_tests))]
#![cfg(not(miri))]
#![recursion_limit = "1024"]
#![feature(rustc_private)]
#![allow(
clippy::blocks_in_conditions,
clippy::doc_markdown,
clippy::explicit_deref_methods,
clippy::let_underscore_untyped,
clippy::manual_assert,
clippy::manual_let_else,
clippy::match_like_matches_macro,
clippy::match_wildcard_for_single_variants,
clippy::too_many_lines,
clippy::uninlined_format_args
)]
extern crate rustc_ast;
extern crate rustc_ast_pretty;
extern crate rustc_data_structures;
extern crate rustc_driver;
extern crate rustc_span;
extern crate smallvec;
extern crate thin_vec;
use crate::common::eq::SpanlessEq;
use crate::common::parse;
use quote::ToTokens;
use rustc_ast::ast;
use rustc_ast::ptr::P;
use rustc_ast_pretty::pprust;
use rustc_span::edition::Edition;
use std::fs;
use std::path::Path;
use std::process;
use std::sync::atomic::{AtomicUsize, Ordering};
#[macro_use]
mod macros;
mod common;
mod repo;
#[test]
fn test_rustc_precedence() {
repo::rayon_init();
repo::clone_rust();
let abort_after = repo::abort_after();
if abort_after == 0 {
panic!("skipping all precedence tests");
}
let passed = AtomicUsize::new(0);
let failed = AtomicUsize::new(0);
repo::for_each_rust_file(|path| {
let content = fs::read_to_string(path).unwrap();
let (l_passed, l_failed) = match syn::parse_file(&content) {
Ok(file) => {
let edition = repo::edition(path).parse().unwrap();
let exprs = collect_exprs(file);
let (l_passed, l_failed) = test_expressions(path, edition, exprs);
errorf!(
"=== {}: {} passed | {} failed\n",
path.display(),
l_passed,
l_failed,
);
(l_passed, l_failed)
}
Err(msg) => {
errorf!("\nFAIL {} - syn failed to parse: {}\n", path.display(), msg);
(0, 1)
}
};
passed.fetch_add(l_passed, Ordering::Relaxed);
let prev_failed = failed.fetch_add(l_failed, Ordering::Relaxed);
if prev_failed + l_failed >= abort_after {
process::exit(1);
}
});
let passed = passed.into_inner();
let failed = failed.into_inner();
errorf!("\n===== Precedence Test Results =====\n");
errorf!("{} passed | {} failed\n", passed, failed);
if failed > 0 {
panic!("{} failures", failed);
}
}
fn test_expressions(path: &Path, edition: Edition, exprs: Vec<syn::Expr>) -> (usize, usize) {
let mut passed = 0;
let mut failed = 0;
rustc_span::create_session_if_not_set_then(edition, |_| {
for expr in exprs {
let source_code = expr.to_token_stream().to_string();
let librustc_ast = if let Some(e) = librustc_parse_and_rewrite(&source_code) {
e
} else {
failed += 1;
errorf!(
"\nFAIL {} - librustc failed to parse original\n",
path.display(),
);
continue;
};
let syn_parenthesized_code =
syn_parenthesize(expr.clone()).to_token_stream().to_string();
let syn_ast = if let Some(e) = parse::librustc_expr(&syn_parenthesized_code) {
e
} else {
failed += 1;
errorf!(
"\nFAIL {} - librustc failed to parse parenthesized\n",
path.display(),
);
continue;
};
if !SpanlessEq::eq(&syn_ast, &librustc_ast) {
failed += 1;
let syn_pretty = pprust::expr_to_string(&syn_ast);
let librustc_pretty = pprust::expr_to_string(&librustc_ast);
errorf!(
"\nFAIL {}\n{}\nsyn != rustc\n{}\n",
path.display(),
syn_pretty,
librustc_pretty,
);
continue;
}
let expr_invisible = make_parens_invisible(expr);
let Ok(reparsed_expr_invisible) = syn::parse2(expr_invisible.to_token_stream()) else {
failed += 1;
errorf!(
"\nFAIL {} - syn failed to parse invisible delimiters\n{}\n",
path.display(),
source_code,
);
continue;
};
if expr_invisible != reparsed_expr_invisible {
failed += 1;
errorf!(
"\nFAIL {} - mismatch after parsing invisible delimiters\n{}\n",
path.display(),
source_code,
);
continue;
}
passed += 1;
}
});
(passed, failed)
}
fn librustc_parse_and_rewrite(input: &str) -> Option<P<ast::Expr>> {
parse::librustc_expr(input).map(librustc_parenthesize)
}
fn librustc_parenthesize(mut librustc_expr: P<ast::Expr>) -> P<ast::Expr> {
use rustc_ast::ast::{
AssocItem, AssocItemKind, Attribute, BinOpKind, Block, BorrowKind, BoundConstness, Expr,
ExprField, ExprKind, GenericArg, GenericBound, Local, LocalKind, Pat, Stmt, StmtKind,
StructExpr, StructRest, TraitBoundModifiers, Ty,
};
use rustc_ast::mut_visit::{walk_flat_map_item, MutVisitor};
use rustc_ast::visit::{AssocCtxt, BoundKind};
use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
use rustc_span::DUMMY_SP;
use smallvec::SmallVec;
use std::mem;
use std::ops::DerefMut;
use thin_vec::ThinVec;
struct FullyParenthesize;
fn contains_let_chain(expr: &Expr) -> bool {
match &expr.kind {
ExprKind::Let(..) => true,
ExprKind::Binary(binop, left, right) => {
binop.node == BinOpKind::And
&& (contains_let_chain(left) || contains_let_chain(right))
}
_ => false,
}
}
fn flat_map_field<T: MutVisitor>(mut f: ExprField, vis: &mut T) -> Vec<ExprField> {
if f.is_shorthand {
noop_visit_expr(&mut f.expr, vis);
} else {
vis.visit_expr(&mut f.expr);
}
vec![f]
}
fn flat_map_stmt<T: MutVisitor>(stmt: Stmt, vis: &mut T) -> Vec<Stmt> {
let kind = match stmt.kind {
// Don't wrap toplevel expressions in statements.
StmtKind::Expr(mut e) => {
noop_visit_expr(&mut e, vis);
StmtKind::Expr(e)
}
StmtKind::Semi(mut e) => {
noop_visit_expr(&mut e, vis);
StmtKind::Semi(e)
}
s => s,
};
vec![Stmt { kind, ..stmt }]
}
fn noop_visit_expr<T: MutVisitor>(e: &mut Expr, vis: &mut T) {
match &mut e.kind {
ExprKind::AddrOf(BorrowKind::Raw, ..) | ExprKind::Become(..) => {}
ExprKind::Struct(expr) => {
let StructExpr {
qself,
path,
fields,
rest,
} = expr.deref_mut();
vis.visit_qself(qself);
vis.visit_path(path);
fields.flat_map_in_place(|field| flat_map_field(field, vis));
if let StructRest::Base(rest) = rest {
vis.visit_expr(rest);
}
}
_ => rustc_ast::mut_visit::walk_expr(vis, e),
}
}
impl MutVisitor for FullyParenthesize {
fn visit_expr(&mut self, e: &mut P<Expr>) {
noop_visit_expr(e, self);
match e.kind {
ExprKind::Block(..) | ExprKind::If(..) | ExprKind::Let(..) => {}
ExprKind::Binary(..) if contains_let_chain(e) => {}
_ => {
let inner = mem::replace(
e,
P(Expr {
id: ast::DUMMY_NODE_ID,
kind: ExprKind::Dummy,
span: DUMMY_SP,
attrs: ThinVec::new(),
tokens: None,
}),
);
e.kind = ExprKind::Paren(inner);
}
}
}
fn visit_generic_arg(&mut self, arg: &mut GenericArg) {
match arg {
GenericArg::Lifetime(_lifetime) => {}
GenericArg::Type(arg) => self.visit_ty(arg),
// Don't wrap unbraced const generic arg as that's invalid syntax.
GenericArg::Const(anon_const) => {
if let ExprKind::Block(..) = &mut anon_const.value.kind {
noop_visit_expr(&mut anon_const.value, self);
}
}
}
}
fn visit_param_bound(&mut self, bound: &mut GenericBound, _ctxt: BoundKind) {
match bound {
GenericBound::Trait(
_,
TraitBoundModifiers {
constness: BoundConstness::Maybe(_),
..
},
)
| GenericBound::Outlives(..)
| GenericBound::Use(..) => {}
GenericBound::Trait(ty, _modifier) => self.visit_poly_trait_ref(ty),
}
}
fn visit_block(&mut self, block: &mut P<Block>) {
self.visit_id(&mut block.id);
block
.stmts
.flat_map_in_place(|stmt| flat_map_stmt(stmt, self));
self.visit_span(&mut block.span);
}
fn visit_local(&mut self, local: &mut P<Local>) {
match &mut local.kind {
LocalKind::Decl => {}
LocalKind::Init(init) => {
self.visit_expr(init);
}
LocalKind::InitElse(init, els) => {
self.visit_expr(init);
self.visit_block(els);
}
}
}
fn flat_map_assoc_item(
&mut self,
item: P<AssocItem>,
_ctxt: AssocCtxt,
) -> SmallVec<[P<AssocItem>; 1]> {
match &item.kind {
AssocItemKind::Const(const_item)
if !const_item.generics.params.is_empty()
|| !const_item.generics.where_clause.predicates.is_empty() =>
{
SmallVec::from([item])
}
_ => walk_flat_map_item(self, item),
}
}
// We don't want to look at expressions that might appear in patterns or
// types yet. We'll look into comparing those in the future. For now
// focus on expressions appearing in other places.
fn visit_pat(&mut self, pat: &mut P<Pat>) {
let _ = pat;
}
fn visit_ty(&mut self, ty: &mut P<Ty>) {
let _ = ty;
}
fn visit_attribute(&mut self, attr: &mut Attribute) {
let _ = attr;
}
}
let mut folder = FullyParenthesize;
folder.visit_expr(&mut librustc_expr);
librustc_expr
}
fn syn_parenthesize(syn_expr: syn::Expr) -> syn::Expr {
use syn::fold::{fold_expr, fold_generic_argument, Fold};
use syn::{token, BinOp, Expr, ExprParen, GenericArgument, MetaNameValue, Pat, Stmt, Type};
struct FullyParenthesize;
fn parenthesize(expr: Expr) -> Expr {
Expr::Paren(ExprParen {
attrs: Vec::new(),
expr: Box::new(expr),
paren_token: token::Paren::default(),
})
}
fn needs_paren(expr: &Expr) -> bool {
match expr {
Expr::Group(_) => unreachable!(),
Expr::If(_) | Expr::Unsafe(_) | Expr::Block(_) | Expr::Let(_) => false,
Expr::Binary(_) => !contains_let_chain(expr),
_ => true,
}
}
fn contains_let_chain(expr: &Expr) -> bool {
match expr {
Expr::Let(_) => true,
Expr::Binary(expr) => {
matches!(expr.op, BinOp::And(_))
&& (contains_let_chain(&expr.left) || contains_let_chain(&expr.right))
}
_ => false,
}
}
impl Fold for FullyParenthesize {
fn fold_expr(&mut self, expr: Expr) -> Expr {
let needs_paren = needs_paren(&expr);
let folded = fold_expr(self, expr);
if needs_paren {
parenthesize(folded)
} else {
folded
}
}
fn fold_generic_argument(&mut self, arg: GenericArgument) -> GenericArgument {
match arg {
GenericArgument::Const(arg) => GenericArgument::Const(match arg {
Expr::Block(_) => fold_expr(self, arg),
// Don't wrap unbraced const generic arg as that's invalid syntax.
_ => arg,
}),
_ => fold_generic_argument(self, arg),
}
}
fn fold_stmt(&mut self, stmt: Stmt) -> Stmt {
match stmt {
// Don't wrap toplevel expressions in statements.
Stmt::Expr(Expr::Verbatim(_), Some(_)) => stmt,
Stmt::Expr(e, semi) => Stmt::Expr(fold_expr(self, e), semi),
s => s,
}
}
fn fold_meta_name_value(&mut self, meta: MetaNameValue) -> MetaNameValue {
// Don't turn #[p = "..."] into #[p = ("...")].
meta
}
// We don't want to look at expressions that might appear in patterns or
// types yet. We'll look into comparing those in the future. For now
// focus on expressions appearing in other places.
fn fold_pat(&mut self, pat: Pat) -> Pat {
pat
}
fn fold_type(&mut self, ty: Type) -> Type {
ty
}
}
let mut folder = FullyParenthesize;
folder.fold_expr(syn_expr)
}
fn make_parens_invisible(expr: syn::Expr) -> syn::Expr {
use syn::fold::{fold_expr, fold_stmt, Fold};
use syn::{token, Expr, ExprGroup, ExprParen, Stmt};
struct MakeParensInvisible;
impl Fold for MakeParensInvisible {
fn fold_expr(&mut self, mut expr: Expr) -> Expr {
if let Expr::Paren(paren) = expr {
expr = Expr::Group(ExprGroup {
attrs: paren.attrs,
group_token: token::Group(paren.paren_token.span.join()),
expr: paren.expr,
});
}
fold_expr(self, expr)
}
fn fold_stmt(&mut self, stmt: Stmt) -> Stmt {
if let Stmt::Expr(expr @ (Expr::Binary(_) | Expr::Call(_) | Expr::Cast(_)), None) = stmt
{
Stmt::Expr(
Expr::Paren(ExprParen {
attrs: Vec::new(),
paren_token: token::Paren::default(),
expr: Box::new(fold_expr(self, expr)),
}),
None,
)
} else {
fold_stmt(self, stmt)
}
}
}
let mut folder = MakeParensInvisible;
folder.fold_expr(expr)
}
/// Walk through a crate collecting all expressions we can find in it.
fn collect_exprs(file: syn::File) -> Vec<syn::Expr> {
use syn::fold::Fold;
use syn::punctuated::Punctuated;
use syn::{token, ConstParam, Expr, ExprTuple, Pat, Path};
struct CollectExprs(Vec<Expr>);
impl Fold for CollectExprs {
fn fold_expr(&mut self, expr: Expr) -> Expr {
match expr {
Expr::Verbatim(_) => {}
_ => self.0.push(expr),
}
Expr::Tuple(ExprTuple {
attrs: vec![],
elems: Punctuated::new(),
paren_token: token::Paren::default(),
})
}
fn fold_pat(&mut self, pat: Pat) -> Pat {
pat
}
fn fold_path(&mut self, path: Path) -> Path {
// Skip traversing into const generic path arguments
path
}
fn fold_const_param(&mut self, const_param: ConstParam) -> ConstParam {
const_param
}
}
let mut folder = CollectExprs(vec![]);
folder.fold_file(file);
folder.0
}
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