clippy_lints/src/utils/author.rs

   1 //! A group of attributes that can be attached to Rust code in order
   2 //! to generate a clippy lint detecting said code automatically.
   3
   4 #![allow(print_stdout, use_debug)]
   5
   6 use rustc::lint::*;
   7 use rustc::hir;
   8 use rustc::hir::{Expr, Expr_, QPath, Ty_, Pat, PatKind, BindingAnnotation, StmtSemi, StmtExpr, StmtDecl, Decl_, Stmt};
   9 use rustc::hir::intravisit::{NestedVisitorMap, Visitor};
  10 use syntax::ast::{Attribute, LitKind, DUMMY_NODE_ID};
  11 use std::collections::HashMap;
  12 use crate::utils::get_attr;
  13
  14 /// **What it does:** Generates clippy code that detects the offending pattern
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// // ./tests/ui/my_lint.rs
  19 /// fn foo() {
  20 ///     // detect the following pattern
  21 ///     #[clippy::author]
  22 ///     if x == 42 {
  23 ///         // but ignore everything from here on
  24 ///         #![clippy::author = "ignore"]
  25 ///     }
  26 /// }
  27 /// ```
  28 ///
  29 /// Running `TESTNAME=ui/my_lint cargo test --test compile-test` will produce
  30 /// a `./tests/ui/new_lint.stdout` file with the generated code:
  31 ///
  32 /// ```rust
  33 /// // ./tests/ui/new_lint.stdout
  34 /// if_chain!{
  35 ///     if let Expr_::ExprIf(ref cond, ref then, None) = item.node,
  36 ///     if let Expr_::ExprBinary(BinOp::Eq, ref left, ref right) = cond.node,
  37 ///     if let Expr_::ExprPath(ref path) = left.node,
  38 ///     if let Expr_::ExprLit(ref lit) = right.node,
  39 ///     if let LitKind::Int(42, _) = lit.node,
  40 ///     then {
  41 ///         // report your lint here
  42 ///     }
  43 /// }
  44 /// ```
  45 declare_clippy_lint! {
  46     pub LINT_AUTHOR,
  47     internal_warn,
  48     "helper for writing lints"
  49 }
  50
  51 pub struct Pass;
  52
  53 impl LintPass for Pass {
  54     fn get_lints(&self) -> LintArray {
  55         lint_array!(LINT_AUTHOR)
  56     }
  57 }
  58
  59 fn prelude() {
  60     println!("if_chain! {{");
  61 }
  62
  63 fn done() {
  64     println!("    then {{");
  65     println!("        // report your lint here");
  66     println!("    }}");
  67     println!("}}");
  68 }
  69
  70 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
  71     fn check_item(&mut self, _cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
  72         if !has_attr(&item.attrs) {
  73             return;
  74         }
  75         prelude();
  76         PrintVisitor::new("item").visit_item(item);
  77         done();
  78     }
  79
  80     fn check_impl_item(&mut self, _cx: &LateContext<'a, 'tcx>, item: &'tcx hir::ImplItem) {
  81         if !has_attr(&item.attrs) {
  82             return;
  83         }
  84         prelude();
  85         PrintVisitor::new("item").visit_impl_item(item);
  86         done();
  87     }
  88
  89     fn check_trait_item(&mut self, _cx: &LateContext<'a, 'tcx>, item: &'tcx hir::TraitItem) {
  90         if !has_attr(&item.attrs) {
  91             return;
  92         }
  93         prelude();
  94         PrintVisitor::new("item").visit_trait_item(item);
  95         done();
  96     }
  97
  98     fn check_variant(&mut self, _cx: &LateContext<'a, 'tcx>, var: &'tcx hir::Variant, generics: &hir::Generics) {
  99         if !has_attr(&var.node.attrs) {
 100             return;
 101         }
 102         prelude();
 103         PrintVisitor::new("var").visit_variant(var, generics, DUMMY_NODE_ID);
 104         done();
 105     }
 106
 107     fn check_struct_field(&mut self, _cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
 108         if !has_attr(&field.attrs) {
 109             return;
 110         }
 111         prelude();
 112         PrintVisitor::new("field").visit_struct_field(field);
 113         done();
 114     }
 115
 116     fn check_expr(&mut self, _cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 117         if !has_attr(&expr.attrs) {
 118             return;
 119         }
 120         prelude();
 121         PrintVisitor::new("expr").visit_expr(expr);
 122         done();
 123     }
 124
 125     fn check_arm(&mut self, _cx: &LateContext<'a, 'tcx>, arm: &'tcx hir::Arm) {
 126         if !has_attr(&arm.attrs) {
 127             return;
 128         }
 129         prelude();
 130         PrintVisitor::new("arm").visit_arm(arm);
 131         done();
 132     }
 133
 134     fn check_stmt(&mut self, _cx: &LateContext<'a, 'tcx>, stmt: &'tcx hir::Stmt) {
 135         if !has_attr(stmt.node.attrs()) {
 136             return;
 137         }
 138         prelude();
 139         PrintVisitor::new("stmt").visit_stmt(stmt);
 140         done();
 141     }
 142
 143     fn check_foreign_item(&mut self, _cx: &LateContext<'a, 'tcx>, item: &'tcx hir::ForeignItem) {
 144         if !has_attr(&item.attrs) {
 145             return;
 146         }
 147         prelude();
 148         PrintVisitor::new("item").visit_foreign_item(item);
 149         done();
 150     }
 151 }
 152
 153 impl PrintVisitor {
 154     fn new(s: &'static str) -> Self {
 155         Self {
 156             ids: HashMap::new(),
 157             current: s.to_owned(),
 158         }
 159     }
 160
 161     fn next(&mut self, s: &'static str) -> String {
 162         use std::collections::hash_map::Entry::*;
 163         match self.ids.entry(s) {
 164             // already there: start numbering from `1`
 165             Occupied(mut occ) => {
 166                 let val = occ.get_mut();
 167                 *val += 1;
 168                 format!("{}{}", s, *val)
 169             },
 170             // not there: insert and return name as given
 171             Vacant(vac) => {
 172                 vac.insert(0);
 173                 s.to_owned()
 174             },
 175         }
 176     }
 177
 178     fn print_qpath(&mut self, path: &QPath) {
 179         print!("    if match_qpath({}, &[", self.current);
 180         print_path(path, &mut true);
 181         println!("]);");
 182     }
 183 }
 184
 185 struct PrintVisitor {
 186     /// Fields are the current index that needs to be appended to pattern
 187     /// binding names
 188     ids: HashMap<&'static str, usize>,
 189     /// the name that needs to be destructured
 190     current: String,
 191 }
 192
 193 impl<'tcx> Visitor<'tcx> for PrintVisitor {
 194     fn visit_expr(&mut self, expr: &Expr) {
 195         print!("    if let Expr_::Expr");
 196         let current = format!("{}.node", self.current);
 197         match expr.node {
 198             Expr_::ExprBox(ref inner) => {
 199                 let inner_pat = self.next("inner");
 200                 println!("Box(ref {}) = {};", inner_pat, current);
 201                 self.current = inner_pat;
 202                 self.visit_expr(inner);
 203             },
 204             Expr_::ExprArray(ref elements) => {
 205                 let elements_pat = self.next("elements");
 206                 println!("Array(ref {}) = {};", elements_pat, current);
 207                 println!("    if {}.len() == {};", elements_pat, elements.len());
 208                 for (i, element) in elements.iter().enumerate() {
 209                     self.current = format!("{}[{}]", elements_pat, i);
 210                     self.visit_expr(element);
 211                 }
 212             },
 213             Expr_::ExprCall(ref _func, ref _args) => {
 214                 println!("Call(ref func, ref args) = {};", current);
 215                 println!("    // unimplemented: `ExprCall` is not further destructured at the moment");
 216             },
 217             Expr_::ExprMethodCall(ref _method_name, ref _generics, ref _args) => {
 218                 println!("MethodCall(ref method_name, ref generics, ref args) = {};", current);
 219                 println!("    // unimplemented: `ExprMethodCall` is not further destructured at the moment");
 220             },
 221             Expr_::ExprTup(ref elements) => {
 222                 let elements_pat = self.next("elements");
 223                 println!("Tup(ref {}) = {};", elements_pat, current);
 224                 println!("    if {}.len() == {};", elements_pat, elements.len());
 225                 for (i, element) in elements.iter().enumerate() {
 226                     self.current = format!("{}[{}]", elements_pat, i);
 227                     self.visit_expr(element);
 228                 }
 229             },
 230             Expr_::ExprBinary(ref op, ref left, ref right) => {
 231                 let op_pat = self.next("op");
 232                 let left_pat = self.next("left");
 233                 let right_pat = self.next("right");
 234                 println!("Binary(ref {}, ref {}, ref {}) = {};", op_pat, left_pat, right_pat, current);
 235                 println!("    if BinOp_::{:?} == {}.node;", op.node, op_pat);
 236                 self.current = left_pat;
 237                 self.visit_expr(left);
 238                 self.current = right_pat;
 239                 self.visit_expr(right);
 240             },
 241             Expr_::ExprUnary(ref op, ref inner) => {
 242                 let inner_pat = self.next("inner");
 243                 println!("Unary(UnOp::{:?}, ref {}) = {};", op, inner_pat, current);
 244                 self.current = inner_pat;
 245                 self.visit_expr(inner);
 246             },
 247             Expr_::ExprLit(ref lit) => {
 248                 let lit_pat = self.next("lit");
 249                 println!("Lit(ref {}) = {};", lit_pat, current);
 250                 match lit.node {
 251                     LitKind::Bool(val) => println!("    if let LitKind::Bool({:?}) = {}.node;", val, lit_pat),
 252                     LitKind::Char(c) => println!("    if let LitKind::Char({:?}) = {}.node;", c, lit_pat),
 253                     LitKind::Byte(b) => println!("    if let LitKind::Byte({}) = {}.node;", b, lit_pat),
 254                     // FIXME: also check int type
 255                     LitKind::Int(i, _) => println!("    if let LitKind::Int({}, _) = {}.node;", i, lit_pat),
 256                     LitKind::Float(..) => println!("    if let LitKind::Float(..) = {}.node;", lit_pat),
 257                     LitKind::FloatUnsuffixed(_) => {
 258                         println!("    if let LitKind::FloatUnsuffixed(_) = {}.node;", lit_pat)
 259                     },
 260                     LitKind::ByteStr(ref vec) => {
 261                         let vec_pat = self.next("vec");
 262                         println!("    if let LitKind::ByteStr(ref {}) = {}.node;", vec_pat, lit_pat);
 263                         println!("    if let [{:?}] = **{};", vec, vec_pat);
 264                     },
 265                     LitKind::Str(ref text, _) => {
 266                         let str_pat = self.next("s");
 267                         println!("    if let LitKind::Str(ref {}) = {}.node;", str_pat, lit_pat);
 268                         println!("    if {}.as_str() == {:?}", str_pat, &*text.as_str())
 269                     },
 270                 }
 271             },
 272             Expr_::ExprCast(ref expr, ref ty) => {
 273                 let cast_pat = self.next("expr");
 274                 let cast_ty = self.next("cast_ty");
 275                 let qp_label = self.next("qp");
 276
 277                 println!("Cast(ref {}, ref {}) = {};", cast_pat, cast_ty, current);
 278                 if let Ty_::TyPath(ref qp) = ty.node {
 279                     println!("    if let Ty_::TyPath(ref {}) = {}.node;", qp_label, cast_ty);
 280                     self.current = qp_label;
 281                     self.print_qpath(qp);
 282                 }
 283                 self.current = cast_pat;
 284                 self.visit_expr(expr);
 285             },
 286             Expr_::ExprType(ref expr, ref _ty) => {
 287                 let cast_pat = self.next("expr");
 288                 println!("Type(ref {}, _) = {};", cast_pat, current);
 289                 self.current = cast_pat;
 290                 self.visit_expr(expr);
 291             },
 292             Expr_::ExprIf(ref cond, ref then, ref opt_else) => {
 293                 let cond_pat = self.next("cond");
 294                 let then_pat = self.next("then");
 295                 if let Some(ref else_) = *opt_else {
 296                     let else_pat = self.next("else_");
 297                     println!("If(ref {}, ref {}, Some(ref {})) = {};", cond_pat, then_pat, else_pat, current);
 298                     self.current = else_pat;
 299                     self.visit_expr(else_);
 300                 } else {
 301                     println!("If(ref {}, ref {}, None) = {};", cond_pat, then_pat, current);
 302                 }
 303                 self.current = cond_pat;
 304                 self.visit_expr(cond);
 305                 self.current = then_pat;
 306                 self.visit_expr(then);
 307             },
 308             Expr_::ExprWhile(ref cond, ref body, _) => {
 309                 let cond_pat = self.next("cond");
 310                 let body_pat = self.next("body");
 311                 let label_pat = self.next("label");
 312                 println!("While(ref {}, ref {}, ref {}) = {};", cond_pat, body_pat, label_pat, current);
 313                 self.current = cond_pat;
 314                 self.visit_expr(cond);
 315                 self.current = body_pat;
 316                 self.visit_block(body);
 317             },
 318             Expr_::ExprLoop(ref body, _, desugaring) => {
 319                 let body_pat = self.next("body");
 320                 let des = loop_desugaring_name(desugaring);
 321                 let label_pat = self.next("label");
 322                 println!("Loop(ref {}, ref {}, {}) = {};", body_pat, label_pat, des, current);
 323                 self.current = body_pat;
 324                 self.visit_block(body);
 325             },
 326             Expr_::ExprMatch(ref expr, ref arms, desugaring) => {
 327                 let des = desugaring_name(desugaring);
 328                 let expr_pat = self.next("expr");
 329                 let arms_pat = self.next("arms");
 330                 println!("Match(ref {}, ref {}, {}) = {};", expr_pat, arms_pat, des, current);
 331                 self.current = expr_pat;
 332                 self.visit_expr(expr);
 333                 println!("    if {}.len() == {};", arms_pat, arms.len());
 334                 for (i, arm) in arms.iter().enumerate() {
 335                     self.current = format!("{}[{}].body", arms_pat, i);
 336                     self.visit_expr(&arm.body);
 337                     if let Some(ref guard) = arm.guard {
 338                         let guard_pat = self.next("guard");
 339                         println!("    if let Some(ref {}) = {}[{}].guard", guard_pat, arms_pat, i);
 340                         self.current = guard_pat;
 341                         self.visit_expr(guard);
 342                     }
 343                     println!("    if {}[{}].pats.len() == {};", arms_pat, i, arm.pats.len());
 344                     for (j, pat) in arm.pats.iter().enumerate() {
 345                         self.current = format!("{}[{}].pats[{}]", arms_pat, i, j);
 346                         self.visit_pat(pat);
 347                     }
 348                 }
 349             },
 350             Expr_::ExprClosure(ref _capture_clause, ref _func, _, _, _) => {
 351                 println!("Closure(ref capture_clause, ref func, _, _, _) = {};", current);
 352                 println!("    // unimplemented: `ExprClosure` is not further destructured at the moment");
 353             },
 354             Expr_::ExprYield(ref sub) => {
 355                 let sub_pat = self.next("sub");
 356                 println!("Yield(ref sub) = {};", current);
 357                 self.current = sub_pat;
 358                 self.visit_expr(sub);
 359             },
 360             Expr_::ExprBlock(ref block, _) => {
 361                 let block_pat = self.next("block");
 362                 println!("Block(ref {}) = {};", block_pat, current);
 363                 self.current = block_pat;
 364                 self.visit_block(block);
 365             },
 366             Expr_::ExprAssign(ref target, ref value) => {
 367                 let target_pat = self.next("target");
 368                 let value_pat = self.next("value");
 369                 println!("Assign(ref {}, ref {}) = {};", target_pat, value_pat, current);
 370                 self.current = target_pat;
 371                 self.visit_expr(target);
 372                 self.current = value_pat;
 373                 self.visit_expr(value);
 374             },
 375             Expr_::ExprAssignOp(ref op, ref target, ref value) => {
 376                 let op_pat = self.next("op");
 377                 let target_pat = self.next("target");
 378                 let value_pat = self.next("value");
 379                 println!("AssignOp(ref {}, ref {}, ref {}) = {};", op_pat, target_pat, value_pat, current);
 380                 println!("    if BinOp_::{:?} == {}.node;", op.node, op_pat);
 381                 self.current = target_pat;
 382                 self.visit_expr(target);
 383                 self.current = value_pat;
 384                 self.visit_expr(value);
 385             },
 386             Expr_::ExprField(ref object, ref field_ident) => {
 387                 let obj_pat = self.next("object");
 388                 let field_name_pat = self.next("field_name");
 389                 println!("Field(ref {}, ref {}) = {};", obj_pat, field_name_pat, current);
 390                 println!("    if {}.node.as_str() == {:?}", field_name_pat, field_ident.name.as_str());
 391                 self.current = obj_pat;
 392                 self.visit_expr(object);
 393             },
 394             Expr_::ExprIndex(ref object, ref index) => {
 395                 let object_pat = self.next("object");
 396                 let index_pat = self.next("index");
 397                 println!("Index(ref {}, ref {}) = {};", object_pat, index_pat, current);
 398                 self.current = object_pat;
 399                 self.visit_expr(object);
 400                 self.current = index_pat;
 401                 self.visit_expr(index);
 402             },
 403             Expr_::ExprPath(ref path) => {
 404                 let path_pat = self.next("path");
 405                 println!("Path(ref {}) = {};", path_pat, current);
 406                 self.current = path_pat;
 407                 self.print_qpath(path);
 408             },
 409             Expr_::ExprAddrOf(mutability, ref inner) => {
 410                 let inner_pat = self.next("inner");
 411                 println!("AddrOf({:?}, ref {}) = {};", mutability, inner_pat, current);
 412                 self.current = inner_pat;
 413                 self.visit_expr(inner);
 414             },
 415             Expr_::ExprBreak(ref _destination, ref opt_value) => {
 416                 let destination_pat = self.next("destination");
 417                 if let Some(ref value) = *opt_value {
 418                     let value_pat = self.next("value");
 419                     println!("Break(ref {}, Some(ref {})) = {};", destination_pat, value_pat, current);
 420                     self.current = value_pat;
 421                     self.visit_expr(value);
 422                 } else {
 423                     println!("Break(ref {}, None) = {};", destination_pat, current);
 424                 }
 425                 // FIXME: implement label printing
 426             },
 427             Expr_::ExprAgain(ref _destination) => {
 428                 let destination_pat = self.next("destination");
 429                 println!("Again(ref {}) = {};", destination_pat, current);
 430                 // FIXME: implement label printing
 431             },
 432             Expr_::ExprRet(ref opt_value) => if let Some(ref value) = *opt_value {
 433                 let value_pat = self.next("value");
 434                 println!("Ret(Some(ref {})) = {};", value_pat, current);
 435                 self.current = value_pat;
 436                 self.visit_expr(value);
 437             } else {
 438                 println!("Ret(None) = {};", current);
 439             },
 440             Expr_::ExprInlineAsm(_, ref _input, ref _output) => {
 441                 println!("InlineAsm(_, ref input, ref output) = {};", current);
 442                 println!("    // unimplemented: `ExprInlineAsm` is not further destructured at the moment");
 443             },
 444             Expr_::ExprStruct(ref path, ref fields, ref opt_base) => {
 445                 let path_pat = self.next("path");
 446                 let fields_pat = self.next("fields");
 447                 if let Some(ref base) = *opt_base {
 448                     let base_pat = self.next("base");
 449                     println!(
 450                         "Struct(ref {}, ref {}, Some(ref {})) = {};",
 451                         path_pat,
 452                         fields_pat,
 453                         base_pat,
 454                         current
 455                     );
 456                     self.current = base_pat;
 457                     self.visit_expr(base);
 458                 } else {
 459                     println!("Struct(ref {}, ref {}, None) = {};", path_pat, fields_pat, current);
 460                 }
 461                 self.current = path_pat;
 462                 self.print_qpath(path);
 463                 println!("    if {}.len() == {};", fields_pat, fields.len());
 464                 println!("    // unimplemented: field checks");
 465             },
 466             // FIXME: compute length (needs type info)
 467             Expr_::ExprRepeat(ref value, _) => {
 468                 let value_pat = self.next("value");
 469                 println!("Repeat(ref {}, _) = {};", value_pat, current);
 470                 println!("// unimplemented: repeat count check");
 471                 self.current = value_pat;
 472                 self.visit_expr(value);
 473             },
 474         }
 475     }
 476
 477     fn visit_pat(&mut self, pat: &Pat) {
 478         print!("    if let PatKind::");
 479         let current = format!("{}.node", self.current);
 480         match pat.node {
 481             PatKind::Wild => println!("Wild = {};", current),
 482             PatKind::Binding(anno, _, name, ref sub) => {
 483                 let anno_pat = match anno {
 484                     BindingAnnotation::Unannotated => "BindingAnnotation::Unannotated",
 485                     BindingAnnotation::Mutable => "BindingAnnotation::Mutable",
 486                     BindingAnnotation::Ref => "BindingAnnotation::Ref",
 487                     BindingAnnotation::RefMut => "BindingAnnotation::RefMut",
 488                 };
 489                 let name_pat = self.next("name");
 490                 if let Some(ref sub) = *sub {
 491                     let sub_pat = self.next("sub");
 492                     println!("Binding({}, _, {}, Some(ref {})) = {};", anno_pat, name_pat, sub_pat, current);
 493                     self.current = sub_pat;
 494                     self.visit_pat(sub);
 495                 } else {
 496                     println!("Binding({}, _, {}, None) = {};", anno_pat, name_pat, current);
 497                 }
 498                 println!("    if {}.node.as_str() == \"{}\";", name_pat, name.node.as_str());
 499             }
 500             PatKind::Struct(ref path, ref fields, ignore) => {
 501                 let path_pat = self.next("path");
 502                 let fields_pat = self.next("fields");
 503                 println!("Struct(ref {}, ref {}, {}) = {};", path_pat, fields_pat, ignore, current);
 504                 self.current = path_pat;
 505                 self.print_qpath(path);
 506                 println!("    if {}.len() == {};", fields_pat, fields.len());
 507                 println!("    // unimplemented: field checks");
 508             }
 509             PatKind::TupleStruct(ref path, ref fields, skip_pos) => {
 510                 let path_pat = self.next("path");
 511                 let fields_pat = self.next("fields");
 512                 println!("TupleStruct(ref {}, ref {}, {:?}) = {};", path_pat, fields_pat, skip_pos, current);
 513                 self.current = path_pat;
 514                 self.print_qpath(path);
 515                 println!("    if {}.len() == {};", fields_pat, fields.len());
 516                 println!("    // unimplemented: field checks");
 517             },
 518             PatKind::Path(ref path) => {
 519                 let path_pat = self.next("path");
 520                 println!("Path(ref {}) = {};", path_pat, current);
 521                 self.current = path_pat;
 522                 self.print_qpath(path);
 523             }
 524             PatKind::Tuple(ref fields, skip_pos) => {
 525                 let fields_pat = self.next("fields");
 526                 println!("Tuple(ref {}, {:?}) = {};", fields_pat, skip_pos, current);
 527                 println!("    if {}.len() == {};", fields_pat, fields.len());
 528                 println!("    // unimplemented: field checks");
 529             }
 530             PatKind::Box(ref pat) => {
 531                 let pat_pat = self.next("pat");
 532                 println!("Box(ref {}) = {};", pat_pat, current);
 533                 self.current = pat_pat;
 534                 self.visit_pat(pat);
 535             },
 536             PatKind::Ref(ref pat, muta) => {
 537                 let pat_pat = self.next("pat");
 538                 println!("Ref(ref {}, Mutability::{:?}) = {};", pat_pat, muta, current);
 539                 self.current = pat_pat;
 540                 self.visit_pat(pat);
 541             },
 542             PatKind::Lit(ref lit_expr) => {
 543                 let lit_expr_pat = self.next("lit_expr");
 544                 println!("Lit(ref {}) = {}", lit_expr_pat, current);
 545                 self.current = lit_expr_pat;
 546                 self.visit_expr(lit_expr);
 547             }
 548             PatKind::Range(ref start, ref end, end_kind) => {
 549                 let start_pat = self.next("start");
 550                 let end_pat = self.next("end");
 551                 println!("Range(ref {}, ref {}, RangeEnd::{:?}) = {};", start_pat, end_pat, end_kind, current);
 552                 self.current = start_pat;
 553                 self.visit_expr(start);
 554                 self.current = end_pat;
 555                 self.visit_expr(end);
 556             }
 557             PatKind::Slice(ref start, ref middle, ref end) => {
 558                 let start_pat = self.next("start");
 559                 let end_pat = self.next("end");
 560                 if let Some(ref middle) = middle {
 561                     let middle_pat = self.next("middle");
 562                     println!("Slice(ref {}, Some(ref {}), ref {}) = {};", start_pat, middle_pat, end_pat, current);
 563                     self.current = middle_pat;
 564                     self.visit_pat(middle);
 565                 } else {
 566                     println!("Slice(ref {}, None, ref {}) = {};", start_pat, end_pat, current);
 567                 }
 568                 println!("    if {}.len() == {};", start_pat, start.len());
 569                 for (i, pat) in start.iter().enumerate() {
 570                     self.current = format!("{}[{}]", start_pat, i);
 571                     self.visit_pat(pat);
 572                 }
 573                 println!("    if {}.len() == {};", end_pat, end.len());
 574                 for (i, pat) in end.iter().enumerate() {
 575                     self.current = format!("{}[{}]", end_pat, i);
 576                     self.visit_pat(pat);
 577                 }
 578             }
 579         }
 580     }
 581
 582     fn visit_stmt(&mut self, s: &Stmt) {
 583         print!("    if let Stmt_::");
 584         let current = format!("{}.node", self.current);
 585         match s.node {
 586             // Could be an item or a local (let) binding:
 587             StmtDecl(ref decl, _) => {
 588                 let decl_pat = self.next("decl");
 589                 println!("StmtDecl(ref {}, _) = {}", decl_pat, current);
 590                 print!("    if let Decl_::");
 591                 let current = format!("{}.node", decl_pat);
 592                 match decl.node {
 593                     // A local (let) binding:
 594                     Decl_::DeclLocal(ref local) => {
 595                         let local_pat = self.next("local");
 596                         println!("DeclLocal(ref {}) = {};", local_pat, current);
 597                         if let Some(ref init) = local.init {
 598                             let init_pat = self.next("init");
 599                             println!("    if let Some(ref {}) = {}.init", init_pat, local_pat);
 600                             self.current = init_pat;
 601                             self.visit_expr(init);
 602                         }
 603                         self.current = format!("{}.pat", local_pat);
 604                         self.visit_pat(&local.pat);
 605                     },
 606                     // An item binding:
 607                     Decl_::DeclItem(_) => {
 608                         println!("DeclItem(item_id) = {};", current);
 609                     },
 610                 }
 611             }
 612
 613             // Expr without trailing semi-colon (must have unit type):
 614             StmtExpr(ref e, _) => {
 615                 let e_pat = self.next("e");
 616                 println!("StmtExpr(ref {}, _) = {}", e_pat, current);
 617                 self.current = e_pat;
 618                 self.visit_expr(e);
 619             },
 620
 621             // Expr with trailing semi-colon (may have any type):
 622             StmtSemi(ref e, _) => {
 623                 let e_pat = self.next("e");
 624                 println!("StmtSemi(ref {}, _) = {}", e_pat, current);
 625                 self.current = e_pat;
 626                 self.visit_expr(e);
 627             },
 628         }
 629     }
 630
 631     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 632         NestedVisitorMap::None
 633     }
 634 }
 635
 636 fn has_attr(attrs: &[Attribute]) -> bool {
 637     get_attr(attrs, "author").count() > 0
 638 }
 639
 640 fn desugaring_name(des: hir::MatchSource) -> String {
 641     match des {
 642         hir::MatchSource::ForLoopDesugar => "MatchSource::ForLoopDesugar".to_string(),
 643         hir::MatchSource::TryDesugar => "MatchSource::TryDesugar".to_string(),
 644         hir::MatchSource::WhileLetDesugar => "MatchSource::WhileLetDesugar".to_string(),
 645         hir::MatchSource::Normal => "MatchSource::Normal".to_string(),
 646         hir::MatchSource::IfLetDesugar { contains_else_clause } => format!("MatchSource::IfLetDesugar {{ contains_else_clause: {} }}", contains_else_clause),
 647     }
 648 }
 649
 650 fn loop_desugaring_name(des: hir::LoopSource) -> &'static str {
 651     match des {
 652         hir::LoopSource::ForLoop => "LoopSource::ForLoop",
 653         hir::LoopSource::Loop => "LoopSource::Loop",
 654         hir::LoopSource::WhileLet => "LoopSource::WhileLet",
 655     }
 656 }
 657
 658 fn print_path(path: &QPath, first: &mut bool) {
 659     match *path {
 660         QPath::Resolved(_, ref path) => for segment in &path.segments {
 661             if *first {
 662                 *first = false;
 663             } else {
 664                 print!(", ");
 665             }
 666             print!("{:?}", segment.name.as_str());
 667         },
 668         QPath::TypeRelative(ref ty, ref segment) => match ty.node {
 669             hir::Ty_::TyPath(ref inner_path) => {
 670                 print_path(inner_path, first);
 671                 if *first {
 672                     *first = false;
 673                 } else {
 674                     print!(", ");
 675                 }
 676                 print!("{:?}", segment.name.as_str());
 677             },
 678             ref other => print!("/* unimplemented: {:?}*/", other),
 679         },
 680     }
 681 }