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_pretty;
  23 extern crate rustc_data_structures;
  24 extern crate rustc_ast;
  25 extern crate rustc_parse;
  26 extern crate rustc_session;
  27 extern crate rustc_span;
  28
  29 use rustc_ast_pretty::pprust;
  30 use rustc_data_structures::thin_vec::ThinVec;
  31 use rustc_parse::new_parser_from_source_str;
  32 use rustc_session::parse::ParseSess;
  33 use rustc_span::source_map::{Spanned, DUMMY_SP, FileName};
  34 use rustc_span::source_map::FilePathMapping;
  35 use rustc_span::symbol::Ident;
  36 use rustc_ast::*;
  37 use rustc_ast::mut_visit::{self, MutVisitor, visit_clobber};
  38 use rustc_ast::ptr::P;
  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 = new_parser_from_source_str(
  44         ps,
  45         FileName::Custom(src_as_string.clone()),
  46         src_as_string,
  47     );
  48     p.parse_expr().map_err(|mut e| e.cancel()).ok()
  49 }
  50
  51
  52 // Helper functions for building exprs
  53 fn expr(kind: ExprKind) -> P<Expr> {
  54     P(Expr {
  55         id: DUMMY_NODE_ID,
  56         kind,
  57         span: DUMMY_SP,
  58         attrs: ThinVec::new(),
  59         tokens: None
  60     })
  61 }
  62
  63 fn make_x() -> P<Expr> {
  64     let seg = PathSegment::from_ident(Ident::from_str("x"));
  65     let path = Path { segments: vec![seg], span: DUMMY_SP, tokens: None };
  66     expr(ExprKind::Path(None, path))
  67 }
  68
  69 /// Iterate over exprs of depth up to `depth`. The goal is to explore all "interesting"
  70 /// combinations of expression nesting. For example, we explore combinations using `if`, but not
  71 /// `while` or `match`, since those should print and parse in much the same way as `if`.
  72 fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
  73     if depth == 0 {
  74         f(make_x());
  75         return;
  76     }
  77
  78     let mut g = |e| f(expr(e));
  79
  80     for kind in 0..=19 {
  81         match kind {
  82             0 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Box(e))),
  83             1 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Call(e, vec![]))),
  84             2 => {
  85                 let seg = PathSegment::from_ident(Ident::from_str("x"));
  86                 iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
  87                             seg.clone(), vec![e, make_x()], DUMMY_SP)));
  88                 iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
  89                             seg.clone(), vec![make_x(), e], DUMMY_SP)));
  90             },
  91             3..=8 => {
  92                 let op = Spanned {
  93                     span: DUMMY_SP,
  94                     node: match kind {
  95                         3 => BinOpKind::Add,
  96                         4 => BinOpKind::Mul,
  97                         5 => BinOpKind::Shl,
  98                         6 => BinOpKind::And,
  99                         7 => BinOpKind::Or,
 100                         8 => BinOpKind::Lt,
 101                         _ => unreachable!(),
 102                     }
 103                 };
 104                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x())));
 105                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e)));
 106             },
 107             9 => {
 108                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Unary(UnOp::Deref, e)));
 109             },
 110             10 => {
 111                 let block = P(Block {
 112                     stmts: Vec::new(),
 113                     id: DUMMY_NODE_ID,
 114                     rules: BlockCheckMode::Default,
 115                     span: DUMMY_SP,
 116                     tokens: None,
 117                 });
 118                 iter_exprs(depth - 1, &mut |e| g(ExprKind::If(e, block.clone(), None)));
 119             },
 120             11 => {
 121                 let decl = P(FnDecl {
 122                     inputs: vec![],
 123                     output: FnRetTy::Default(DUMMY_SP),
 124                 });
 125                 iter_exprs(depth - 1, &mut |e| g(
 126                         ExprKind::Closure(CaptureBy::Value,
 127                                           Async::No,
 128                                           Movability::Movable,
 129                                           decl.clone(),
 130                                           e,
 131                                           DUMMY_SP)));
 132             },
 133             12 => {
 134                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(e, make_x(), DUMMY_SP)));
 135                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(make_x(), e, DUMMY_SP)));
 136             },
 137             13 => {
 138                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Field(e, Ident::from_str("f"))));
 139             },
 140             14 => {
 141                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Range(
 142                             Some(e), Some(make_x()), RangeLimits::HalfOpen)));
 143                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Range(
 144                             Some(make_x()), Some(e), RangeLimits::HalfOpen)));
 145             },
 146             15 => {
 147                 iter_exprs(
 148                     depth - 1,
 149                     &mut |e| g(ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, e)),
 150                 );
 151             },
 152             16 => {
 153                 g(ExprKind::Ret(None));
 154                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Ret(Some(e))));
 155             },
 156             17 => {
 157                 let path = Path::from_ident(Ident::from_str("S"));
 158                 g(ExprKind::Struct(P(StructExpr {
 159                     path, fields: vec![], rest: StructRest::Base(make_x())
 160                 })));
 161             },
 162             18 => {
 163                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));
 164             },
 165             19 => {
 166                 let pat = P(Pat {
 167                     id: DUMMY_NODE_ID,
 168                     kind: PatKind::Wild,
 169                     span: DUMMY_SP,
 170                     tokens: None,
 171                 });
 172                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(pat.clone(), e)))
 173             },
 174             _ => panic!("bad counter value in iter_exprs"),
 175         }
 176     }
 177 }
 178
 179
 180 // Folders for manipulating the placement of `Paren` nodes. See below for why this is needed.
 181
 182 /// `MutVisitor` that removes all `ExprKind::Paren` nodes.
 183 struct RemoveParens;
 184
 185 impl MutVisitor for RemoveParens {
 186     fn visit_expr(&mut self, e: &mut P<Expr>) {
 187         match e.kind.clone() {
 188             ExprKind::Paren(inner) => *e = inner,
 189             _ => {}
 190         };
 191         mut_visit::noop_visit_expr(e, self);
 192     }
 193 }
 194
 195
 196 /// `MutVisitor` that inserts `ExprKind::Paren` nodes around every `Expr`.
 197 struct AddParens;
 198
 199 impl MutVisitor for AddParens {
 200     fn visit_expr(&mut self, e: &mut P<Expr>) {
 201         mut_visit::noop_visit_expr(e, self);
 202         visit_clobber(e, |e| {
 203             P(Expr {
 204                 id: DUMMY_NODE_ID,
 205                 kind: ExprKind::Paren(e),
 206                 span: DUMMY_SP,
 207                 attrs: ThinVec::new(),
 208                 tokens: None
 209             })
 210         });
 211     }
 212 }
 213
 214 fn main() {
 215     rustc_span::with_default_session_globals(|| run());
 216 }
 217
 218 fn run() {
 219     let ps = ParseSess::new(FilePathMapping::empty());
 220
 221     iter_exprs(2, &mut |mut e| {
 222         // If the pretty printer is correct, then `parse(print(e))` should be identical to `e`,
 223         // modulo placement of `Paren` nodes.
 224         let printed = pprust::expr_to_string(&e);
 225         println!("printed: {}", printed);
 226
 227         // Ignore expressions with chained comparisons that fail to parse
 228         if let Some(mut parsed) = parse_expr(&ps, &printed) {
 229             // We want to know if `parsed` is structurally identical to `e`, ignoring trivial
 230             // differences like placement of `Paren`s or the exact ranges of node spans.
 231             // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
 232             // everywhere we can, then pretty-print. This should give an unambiguous representation
 233             // of each `Expr`, and it bypasses nearly all of the parenthesization logic, so we
 234             // aren't relying on the correctness of the very thing we're testing.
 235             RemoveParens.visit_expr(&mut e);
 236             AddParens.visit_expr(&mut e);
 237             let text1 = pprust::expr_to_string(&e);
 238             RemoveParens.visit_expr(&mut parsed);
 239             AddParens.visit_expr(&mut parsed);
 240             let text2 = pprust::expr_to_string(&parsed);
 241             assert!(text1 == text2,
 242                     "exprs are not equal:\n  e =      {:?}\n  parsed = {:?}",
 243                     text1, text2);
 244         }
 245     });
 246 }