src/test/ui-fulldeps/pprust-expr-roundtrip.rs

   1 // run-pass
   2 // ignore-cross-compile
   3
   4 // The general idea of this test is to enumerate all "interesting" expressions and check that
   5 // `parse(print(e)) == e` for all `e`. Here's what's interesting, for the purposes of this test:
   6 //
   7 // 1. The test focuses on expression nesting, because interactions between different expression
   8 //    types are harder to test manually than single expression types in isolation.
   9 //
  10 // 2. The test only considers expressions of at most two nontrivial nodes. So it will check `x +
  11 //    x` and `x + (x - x)` but not `(x * x) + (x - x)`. The assumption here is that the correct
  12 //    handling of an expression might depend on the expression's parent, but doesn't depend on its
  13 //    siblings or any more distant ancestors.
  14 //
  15 // 3. The test only checks certain expression kinds. The assumption is that similar expression
  16 //    types, such as `if` and `while` or `+` and `-`, will be handled identically in the printer
  17 //    and parser. So if all combinations of exprs involving `if` work correctly, then combinations
  18 //    using `while`, `if let`, and so on will likely work as well.
  19
  20 #![feature(rustc_private)]
  21
  22 extern crate rustc_ast;
  23 extern crate rustc_ast_pretty;
  24 extern crate rustc_data_structures;
  25 extern crate rustc_parse;
  26 extern crate rustc_session;
  27 extern crate rustc_span;
  28
  29 use rustc_ast::mut_visit::{self, visit_clobber, MutVisitor};
  30 use rustc_ast::ptr::P;
  31 use rustc_ast::*;
  32 use rustc_ast_pretty::pprust;
  33 use rustc_data_structures::thin_vec::ThinVec;
  34 use rustc_parse::new_parser_from_source_str;
  35 use rustc_session::parse::ParseSess;
  36 use rustc_span::source_map::FilePathMapping;
  37 use rustc_span::source_map::{FileName, Spanned, DUMMY_SP};
  38 use rustc_span::symbol::Ident;
  39
  40 fn parse_expr(ps: &ParseSess, src: &str) -> Option<P<Expr>> {
  41     let src_as_string = src.to_string();
  42
  43     let mut p =
  44         new_parser_from_source_str(ps, FileName::Custom(src_as_string.clone()), src_as_string);
  45     p.parse_expr().map_err(|mut e| e.cancel()).ok()
  46 }
  47
  48 // Helper functions for building exprs
  49 fn expr(kind: ExprKind) -> P<Expr> {
  50     P(Expr { id: DUMMY_NODE_ID, kind, span: DUMMY_SP, attrs: ThinVec::new(), tokens: None })
  51 }
  52
  53 fn make_x() -> P<Expr> {
  54     let seg = PathSegment::from_ident(Ident::from_str("x"));
  55     let path = Path { segments: vec![seg], span: DUMMY_SP, tokens: None };
  56     expr(ExprKind::Path(None, path))
  57 }
  58
  59 /// Iterate over exprs of depth up to `depth`. The goal is to explore all "interesting"
  60 /// combinations of expression nesting. For example, we explore combinations using `if`, but not
  61 /// `while` or `match`, since those should print and parse in much the same way as `if`.
  62 fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
  63     if depth == 0 {
  64         f(make_x());
  65         return;
  66     }
  67
  68     let mut g = |e| f(expr(e));
  69
  70     for kind in 0..=19 {
  71         match kind {
  72             0 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Box(e))),
  73             1 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Call(e, vec![]))),
  74             2 => {
  75                 let seg = PathSegment::from_ident(Ident::from_str("x"));
  76                 iter_exprs(depth - 1, &mut |e| {
  77                     g(ExprKind::MethodCall(seg.clone(), vec![e, make_x()], DUMMY_SP))
  78                 });
  79                 iter_exprs(depth - 1, &mut |e| {
  80                     g(ExprKind::MethodCall(seg.clone(), vec![make_x(), e], DUMMY_SP))
  81                 });
  82             }
  83             3..=8 => {
  84                 let op = Spanned {
  85                     span: DUMMY_SP,
  86                     node: match kind {
  87                         3 => BinOpKind::Add,
  88                         4 => BinOpKind::Mul,
  89                         5 => BinOpKind::Shl,
  90                         6 => BinOpKind::And,
  91                         7 => BinOpKind::Or,
  92                         8 => BinOpKind::Lt,
  93                         _ => unreachable!(),
  94                     },
  95                 };
  96                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x())));
  97                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e)));
  98             }
  99             9 => {
 100                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Unary(UnOp::Deref, e)));
 101             }
 102             10 => {
 103                 let block = P(Block {
 104                     stmts: Vec::new(),
 105                     id: DUMMY_NODE_ID,
 106                     rules: BlockCheckMode::Default,
 107                     span: DUMMY_SP,
 108                     tokens: None,
 109                 });
 110                 iter_exprs(depth - 1, &mut |e| g(ExprKind::If(e, block.clone(), None)));
 111             }
 112             11 => {
 113                 let decl = P(FnDecl { inputs: vec![], output: FnRetTy::Default(DUMMY_SP) });
 114                 iter_exprs(depth - 1, &mut |e| {
 115                     g(ExprKind::Closure(
 116                         CaptureBy::Value,
 117                         Async::No,
 118                         Movability::Movable,
 119                         decl.clone(),
 120                         e,
 121                         DUMMY_SP,
 122                     ))
 123                 });
 124             }
 125             12 => {
 126                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(e, make_x(), DUMMY_SP)));
 127                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(make_x(), e, DUMMY_SP)));
 128             }
 129             13 => {
 130                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Field(e, Ident::from_str("f"))));
 131             }
 132             14 => {
 133                 iter_exprs(depth - 1, &mut |e| {
 134                     g(ExprKind::Range(Some(e), Some(make_x()), RangeLimits::HalfOpen))
 135                 });
 136                 iter_exprs(depth - 1, &mut |e| {
 137                     g(ExprKind::Range(Some(make_x()), Some(e), RangeLimits::HalfOpen))
 138                 });
 139             }
 140             15 => {
 141                 iter_exprs(depth - 1, &mut |e| {
 142                     g(ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, e))
 143                 });
 144             }
 145             16 => {
 146                 g(ExprKind::Ret(None));
 147                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Ret(Some(e))));
 148             }
 149             17 => {
 150                 let path = Path::from_ident(Ident::from_str("S"));
 151                 g(ExprKind::Struct(P(StructExpr {
 152                     qself: None,
 153                     path,
 154                     fields: vec![],
 155                     rest: StructRest::Base(make_x()),
 156                 })));
 157             }
 158             18 => {
 159                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));
 160             }
 161             19 => {
 162                 let pat =
 163                     P(Pat { id: DUMMY_NODE_ID, kind: PatKind::Wild, span: DUMMY_SP, tokens: None });
 164                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(pat.clone(), e)))
 165             }
 166             _ => panic!("bad counter value in iter_exprs"),
 167         }
 168     }
 169 }
 170
 171 // Folders for manipulating the placement of `Paren` nodes. See below for why this is needed.
 172
 173 /// `MutVisitor` that removes all `ExprKind::Paren` nodes.
 174 struct RemoveParens;
 175
 176 impl MutVisitor for RemoveParens {
 177     fn visit_expr(&mut self, e: &mut P<Expr>) {
 178         match e.kind.clone() {
 179             ExprKind::Paren(inner) => *e = inner,
 180             _ => {}
 181         };
 182         mut_visit::noop_visit_expr(e, self);
 183     }
 184 }
 185
 186 /// `MutVisitor` that inserts `ExprKind::Paren` nodes around every `Expr`.
 187 struct AddParens;
 188
 189 impl MutVisitor for AddParens {
 190     fn visit_expr(&mut self, e: &mut P<Expr>) {
 191         mut_visit::noop_visit_expr(e, self);
 192         visit_clobber(e, |e| {
 193             P(Expr {
 194                 id: DUMMY_NODE_ID,
 195                 kind: ExprKind::Paren(e),
 196                 span: DUMMY_SP,
 197                 attrs: ThinVec::new(),
 198                 tokens: None,
 199             })
 200         });
 201     }
 202 }
 203
 204 fn main() {
 205     rustc_span::create_default_session_globals_then(|| run());
 206 }
 207
 208 fn run() {
 209     let ps = ParseSess::new(FilePathMapping::empty());
 210
 211     iter_exprs(2, &mut |mut e| {
 212         // If the pretty printer is correct, then `parse(print(e))` should be identical to `e`,
 213         // modulo placement of `Paren` nodes.
 214         let printed = pprust::expr_to_string(&e);
 215         println!("printed: {}", printed);
 216
 217         // Ignore expressions with chained comparisons that fail to parse
 218         if let Some(mut parsed) = parse_expr(&ps, &printed) {
 219             // We want to know if `parsed` is structurally identical to `e`, ignoring trivial
 220             // differences like placement of `Paren`s or the exact ranges of node spans.
 221             // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
 222             // everywhere we can, then pretty-print. This should give an unambiguous representation
 223             // of each `Expr`, and it bypasses nearly all of the parenthesization logic, so we
 224             // aren't relying on the correctness of the very thing we're testing.
 225             RemoveParens.visit_expr(&mut e);
 226             AddParens.visit_expr(&mut e);
 227             let text1 = pprust::expr_to_string(&e);
 228             RemoveParens.visit_expr(&mut parsed);
 229             AddParens.visit_expr(&mut parsed);
 230             let text2 = pprust::expr_to_string(&parsed);
 231             assert!(
 232                 text1 == text2,
 233                 "exprs are not equal:\n  e =      {:?}\n  parsed = {:?}",
 234                 text1,
 235                 text2
 236             );
 237         }
 238     });
 239 }