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_data_structures;
  23 extern crate syntax;
  24
  25 use rustc_data_structures::thin_vec::ThinVec;
  26 use syntax::ast::*;
  27 use syntax::source_map::{Spanned, DUMMY_SP, FileName};
  28 use syntax::source_map::FilePathMapping;
  29 use syntax::mut_visit::{self, MutVisitor, visit_clobber};
  30 use syntax::parse::{self, ParseSess};
  31 use syntax::print::pprust;
  32 use syntax::ptr::P;
  33
  34
  35 fn parse_expr(ps: &ParseSess, src: &str) -> P<Expr> {
  36     let src_as_string = src.to_string();
  37
  38     let mut p = parse::new_parser_from_source_str(ps,
  39                                                   FileName::Custom(src_as_string.clone()),
  40                                                   src_as_string);
  41     p.parse_expr().unwrap()
  42 }
  43
  44
  45 // Helper functions for building exprs
  46 fn expr(kind: ExprKind) -> P<Expr> {
  47     P(Expr {
  48         id: DUMMY_NODE_ID,
  49         node: kind,
  50         span: DUMMY_SP,
  51         attrs: ThinVec::new(),
  52     })
  53 }
  54
  55 fn make_x() -> P<Expr> {
  56     let seg = PathSegment::from_ident(Ident::from_str("x"));
  57     let path = Path { segments: vec![seg], span: DUMMY_SP };
  58     expr(ExprKind::Path(None, path))
  59 }
  60
  61 /// Iterate over exprs of depth up to `depth`. The goal is to explore all "interesting"
  62 /// combinations of expression nesting. For example, we explore combinations using `if`, but not
  63 /// `while` or `match`, since those should print and parse in much the same way as `if`.
  64 fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
  65     if depth == 0 {
  66         f(make_x());
  67         return;
  68     }
  69
  70     let mut g = |e| f(expr(e));
  71
  72     for kind in 0..=19 {
  73         match kind {
  74             0 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Box(e))),
  75             1 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Call(e, vec![]))),
  76             2 => {
  77                 let seg = PathSegment::from_ident(Ident::from_str("x"));
  78                 iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
  79                             seg.clone(), vec![e, make_x()])));
  80                 iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
  81                             seg.clone(), vec![make_x(), e])));
  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                 });
 109                 iter_exprs(depth - 1, &mut |e| g(ExprKind::If(e, block.clone(), None)));
 110             },
 111             11 => {
 112                 let decl = P(FnDecl {
 113                     inputs: vec![],
 114                     output: FunctionRetTy::Default(DUMMY_SP),
 115                     c_variadic: false,
 116                 });
 117                 iter_exprs(depth - 1, &mut |e| g(
 118                         ExprKind::Closure(CaptureBy::Value,
 119                                           IsAsync::NotAsync,
 120                                           Movability::Movable,
 121                                           decl.clone(),
 122                                           e,
 123                                           DUMMY_SP)));
 124             },
 125             12 => {
 126                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(e, make_x())));
 127                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(make_x(), e)));
 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| g(ExprKind::Range(
 134                             Some(e), Some(make_x()), RangeLimits::HalfOpen)));
 135                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Range(
 136                             Some(make_x()), Some(e), RangeLimits::HalfOpen)));
 137             },
 138             15 => {
 139                 iter_exprs(depth - 1, &mut |e| g(ExprKind::AddrOf(Mutability::Immutable, e)));
 140             },
 141             16 => {
 142                 g(ExprKind::Ret(None));
 143                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Ret(Some(e))));
 144             },
 145             17 => {
 146                 let path = Path::from_ident(Ident::from_str("S"));
 147                 g(ExprKind::Struct(path, vec![], Some(make_x())));
 148             },
 149             18 => {
 150                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));
 151             },
 152             19 => {
 153                 let ps = vec![P(Pat {
 154                     id: DUMMY_NODE_ID,
 155                     node: PatKind::Wild,
 156                     span: DUMMY_SP,
 157                 })];
 158                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Let(ps.clone(), e)))
 159             },
 160             _ => panic!("bad counter value in iter_exprs"),
 161         }
 162     }
 163 }
 164
 165
 166 // Folders for manipulating the placement of `Paren` nodes. See below for why this is needed.
 167
 168 /// `MutVisitor` that removes all `ExprKind::Paren` nodes.
 169 struct RemoveParens;
 170
 171 impl MutVisitor for RemoveParens {
 172     fn visit_expr(&mut self, e: &mut P<Expr>) {
 173         match e.node.clone() {
 174             ExprKind::Paren(inner) => *e = inner,
 175             _ => {}
 176         };
 177         mut_visit::noop_visit_expr(e, self);
 178     }
 179 }
 180
 181
 182 /// `MutVisitor` that inserts `ExprKind::Paren` nodes around every `Expr`.
 183 struct AddParens;
 184
 185 impl MutVisitor for AddParens {
 186     fn visit_expr(&mut self, e: &mut P<Expr>) {
 187         mut_visit::noop_visit_expr(e, self);
 188         visit_clobber(e, |e| {
 189             P(Expr {
 190                 id: DUMMY_NODE_ID,
 191                 node: ExprKind::Paren(e),
 192                 span: DUMMY_SP,
 193                 attrs: ThinVec::new(),
 194             })
 195         });
 196     }
 197 }
 198
 199 fn main() {
 200     syntax::with_default_globals(|| run());
 201 }
 202
 203 fn run() {
 204     let ps = ParseSess::new(FilePathMapping::empty());
 205
 206     iter_exprs(2, &mut |mut e| {
 207         // If the pretty printer is correct, then `parse(print(e))` should be identical to `e`,
 208         // modulo placement of `Paren` nodes.
 209         let printed = pprust::expr_to_string(&e);
 210         println!("printed: {}", printed);
 211
 212         let mut parsed = parse_expr(&ps, &printed);
 213
 214         // We want to know if `parsed` is structurally identical to `e`, ignoring trivial
 215         // differences like placement of `Paren`s or the exact ranges of node spans.
 216         // Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
 217         // everywhere we can, then pretty-print. This should give an unambiguous representation of
 218         // each `Expr`, and it bypasses nearly all of the parenthesization logic, so we aren't
 219         // relying on the correctness of the very thing we're testing.
 220         RemoveParens.visit_expr(&mut e);
 221         AddParens.visit_expr(&mut e);
 222         let text1 = pprust::expr_to_string(&e);
 223         RemoveParens.visit_expr(&mut parsed);
 224         AddParens.visit_expr(&mut parsed);
 225         let text2 = pprust::expr_to_string(&parsed);
 226         assert!(text1 == text2,
 227                 "exprs are not equal:\n  e =      {:?}\n  parsed = {:?}",
 228                 text1, text2);
 229     });
 230 }