// run-pass // ignore-cross-compile // The general idea of this test is to enumerate all "interesting" expressions and check that // `parse(print(e)) == e` for all `e`. Here's what's interesting, for the purposes of this test: // // 1. The test focuses on expression nesting, because interactions between different expression // types are harder to test manually than single expression types in isolation. // // 2. The test only considers expressions of at most two nontrivial nodes. So it will check `x + // x` and `x + (x - x)` but not `(x * x) + (x - x)`. The assumption here is that the correct // handling of an expression might depend on the expression's parent, but doesn't depend on its // siblings or any more distant ancestors. // // 3. The test only checks certain expression kinds. The assumption is that similar expression // types, such as `if` and `while` or `+` and `-`, will be handled identically in the printer // and parser. So if all combinations of exprs involving `if` work correctly, then combinations // using `while`, `if let`, and so on will likely work as well. #![feature(rustc_private)] extern crate rustc_ast; extern crate rustc_ast_pretty; extern crate rustc_data_structures; extern crate rustc_parse; extern crate rustc_session; extern crate rustc_span; use rustc_ast::mut_visit::{self, visit_clobber, MutVisitor}; use rustc_ast::ptr::P; use rustc_ast::*; use rustc_ast_pretty::pprust; use rustc_data_structures::thin_vec::ThinVec; use rustc_parse::new_parser_from_source_str; use rustc_session::parse::ParseSess; use rustc_span::source_map::FilePathMapping; use rustc_span::source_map::{FileName, Spanned, DUMMY_SP}; use rustc_span::symbol::Ident; fn parse_expr(ps: &ParseSess, src: &str) -> Option> { let src_as_string = src.to_string(); let mut p = new_parser_from_source_str(ps, FileName::Custom(src_as_string.clone()), src_as_string); p.parse_expr().map_err(|e| e.cancel()).ok() } // Helper functions for building exprs fn expr(kind: ExprKind) -> P { P(Expr { id: DUMMY_NODE_ID, kind, span: DUMMY_SP, attrs: ThinVec::new(), tokens: None }) } fn make_x() -> P { let seg = PathSegment::from_ident(Ident::from_str("x")); let path = Path { segments: vec![seg], span: DUMMY_SP, tokens: None }; expr(ExprKind::Path(None, path)) } /// Iterate over exprs of depth up to `depth`. The goal is to explore all "interesting" /// combinations of expression nesting. For example, we explore combinations using `if`, but not /// `while` or `match`, since those should print and parse in much the same way as `if`. fn iter_exprs(depth: usize, f: &mut dyn FnMut(P)) { if depth == 0 { f(make_x()); return; } let mut g = |e| f(expr(e)); for kind in 0..=19 { match kind { 0 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Box(e))), 1 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Call(e, vec![]))), 2 => { let seg = PathSegment::from_ident(Ident::from_str("x")); iter_exprs(depth - 1, &mut |e| { g(ExprKind::MethodCall(seg.clone(), vec![e, make_x()], DUMMY_SP)) }); iter_exprs(depth - 1, &mut |e| { g(ExprKind::MethodCall(seg.clone(), vec![make_x(), e], DUMMY_SP)) }); } 3..=8 => { let op = Spanned { span: DUMMY_SP, node: match kind { 3 => BinOpKind::Add, 4 => BinOpKind::Mul, 5 => BinOpKind::Shl, 6 => BinOpKind::And, 7 => BinOpKind::Or, 8 => BinOpKind::Lt, _ => unreachable!(), }, }; iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x()))); iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e))); } 9 => { iter_exprs(depth - 1, &mut |e| g(ExprKind::Unary(UnOp::Deref, e))); } 10 => { let block = P(Block { stmts: Vec::new(), id: DUMMY_NODE_ID, rules: BlockCheckMode::Default, span: DUMMY_SP, tokens: None, could_be_bare_literal: false, }); iter_exprs(depth - 1, &mut |e| g(ExprKind::If(e, block.clone(), None))); } 11 => { let decl = P(FnDecl { inputs: vec![], output: FnRetTy::Default(DUMMY_SP) }); iter_exprs(depth - 1, &mut |e| { g(ExprKind::Closure( ClosureBinder::NotPresent, CaptureBy::Value, Async::No, Movability::Movable, decl.clone(), e, DUMMY_SP, )) }); } 12 => { iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(e, make_x(), DUMMY_SP))); iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(make_x(), e, DUMMY_SP))); } 13 => { iter_exprs(depth - 1, &mut |e| g(ExprKind::Field(e, Ident::from_str("f")))); } 14 => { iter_exprs(depth - 1, &mut |e| { g(ExprKind::Range(Some(e), Some(make_x()), RangeLimits::HalfOpen)) }); iter_exprs(depth - 1, &mut |e| { g(ExprKind::Range(Some(make_x()), Some(e), RangeLimits::HalfOpen)) }); } 15 => { iter_exprs(depth - 1, &mut |e| { g(ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, e)) }); } 16 => { g(ExprKind::Ret(None)); iter_exprs(depth - 1, &mut |e| g(ExprKind::Ret(Some(e)))); } 17 => { let path = Path::from_ident(Ident::from_str("S")); g(ExprKind::Struct(P(StructExpr { qself: None, path, fields: vec![], rest: StructRest::Base(make_x()), }))); } 18 => { iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e))); } 19 => { let pat = P(Pat { id: DUMMY_NODE_ID, kind: PatKind::Wild, span: DUMMY_SP, tokens: None }); iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(pat.clone(), e, DUMMY_SP))) } _ => panic!("bad counter value in iter_exprs"), } } } // Folders for manipulating the placement of `Paren` nodes. See below for why this is needed. /// `MutVisitor` that removes all `ExprKind::Paren` nodes. struct RemoveParens; impl MutVisitor for RemoveParens { fn visit_expr(&mut self, e: &mut P) { match e.kind.clone() { ExprKind::Paren(inner) => *e = inner, _ => {} }; mut_visit::noop_visit_expr(e, self); } } /// `MutVisitor` that inserts `ExprKind::Paren` nodes around every `Expr`. struct AddParens; impl MutVisitor for AddParens { fn visit_expr(&mut self, e: &mut P) { mut_visit::noop_visit_expr(e, self); visit_clobber(e, |e| { P(Expr { id: DUMMY_NODE_ID, kind: ExprKind::Paren(e), span: DUMMY_SP, attrs: ThinVec::new(), tokens: None, }) }); } } fn main() { rustc_span::create_default_session_globals_then(|| run()); } fn run() { let ps = ParseSess::new(FilePathMapping::empty()); iter_exprs(2, &mut |mut e| { // If the pretty printer is correct, then `parse(print(e))` should be identical to `e`, // modulo placement of `Paren` nodes. let printed = pprust::expr_to_string(&e); println!("printed: {}", printed); // Ignore expressions with chained comparisons that fail to parse if let Some(mut parsed) = parse_expr(&ps, &printed) { // We want to know if `parsed` is structurally identical to `e`, ignoring trivial // differences like placement of `Paren`s or the exact ranges of node spans. // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s // everywhere we can, then pretty-print. This should give an unambiguous representation // of each `Expr`, and it bypasses nearly all of the parenthesization logic, so we // aren't relying on the correctness of the very thing we're testing. RemoveParens.visit_expr(&mut e); AddParens.visit_expr(&mut e); let text1 = pprust::expr_to_string(&e); RemoveParens.visit_expr(&mut parsed); AddParens.visit_expr(&mut parsed); let text2 = pprust::expr_to_string(&parsed); assert!( text1 == text2, "exprs are not equal:\n e = {:?}\n parsed = {:?}", text1, text2 ); } }); }