src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs

   1 // Here we test that `lowering` behaves correctly wrt. `let $pats = $expr` expressions.
   2 //
   3 // We want to make sure that `let` is banned in situations other than:
   4 //
   5 // expr =
   6 //   | ...
   7 //   | "if" expr_with_let block {"else" block}?
   8 //   | {label ":"}? while" expr_with_let block
   9 //   ;
  10 //
  11 // expr_with_let =
  12 //   | "let" top_pats "=" expr
  13 //   | expr_with_let "&&" expr_with_let
  14 //   | "(" expr_with_let ")"
  15 //   | expr
  16 //   ;
  17 //
  18 // To that end, we check some positions which is not part of the language above.
  19
  20 #![feature(let_chains)] // Avoid inflating `.stderr` with overzealous gates in this test.
  21
  22 #![allow(irrefutable_let_patterns)]
  23
  24 use std::ops::Range;
  25
  26 fn main() {}
  27
  28 fn _if() {
  29     if (let 0 = 1) {}
  30     //~^ ERROR `let` expressions are not supported here
  31
  32     if (((let 0 = 1))) {}
  33     //~^ ERROR `let` expressions are not supported here
  34
  35     if (let 0 = 1) && true {}
  36     //~^ ERROR `let` expressions are not supported here
  37
  38     if true && (let 0 = 1) {}
  39     //~^ ERROR `let` expressions are not supported here
  40
  41     if (let 0 = 1) && (let 0 = 1) {}
  42     //~^ ERROR `let` expressions are not supported here
  43     //~| ERROR `let` expressions are not supported here
  44
  45     if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
  46     //~^ ERROR `let` expressions are not supported here
  47     //~| ERROR `let` expressions are not supported here
  48     //~| ERROR `let` expressions are not supported here
  49 }
  50
  51 fn _while() {
  52     while (let 0 = 1) {}
  53     //~^ ERROR `let` expressions are not supported here
  54
  55     while (((let 0 = 1))) {}
  56     //~^ ERROR `let` expressions are not supported here
  57
  58     while (let 0 = 1) && true {}
  59     //~^ ERROR `let` expressions are not supported here
  60
  61     while true && (let 0 = 1) {}
  62     //~^ ERROR `let` expressions are not supported here
  63
  64     while (let 0 = 1) && (let 0 = 1) {}
  65     //~^ ERROR `let` expressions are not supported here
  66     //~| ERROR `let` expressions are not supported here
  67
  68     while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
  69     //~^ ERROR `let` expressions are not supported here
  70     //~| ERROR `let` expressions are not supported here
  71     //~| ERROR `let` expressions are not supported here
  72 }
  73
  74 fn _macros() {
  75     macro_rules! use_expr {
  76         ($e:expr) => {
  77             if $e {}
  78             while $e {}
  79         }
  80     }
  81     use_expr!((let 0 = 1 && 0 == 0));
  82     //~^ ERROR `let` expressions are not supported here
  83     //~| ERROR `let` expressions are not supported here
  84     use_expr!((let 0 = 1));
  85     //~^ ERROR `let` expressions are not supported here
  86     //~| ERROR `let` expressions are not supported here
  87 }
  88
  89 fn nested_within_if_expr() {
  90     if &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
  91     //~^ ERROR mismatched types
  92
  93     if !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
  94     if *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
  95     //~^ ERROR type `bool` cannot be dereferenced
  96     if -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
  97     //~^ ERROR cannot apply unary operator `-` to type `bool`
  98
  99     fn _check_try_binds_tighter() -> Result<(), ()> {
 100         if let 0 = 0? {}
 101         //~^ ERROR the `?` operator can only be applied to values that implement `Try`
 102         Ok(())
 103     }
 104     if (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
 105     //~^ ERROR the `?` operator can only be applied to values that implement `Try`
 106     //~| ERROR the `?` operator can only be used in a function that returns `Result`
 107
 108     if true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 109     if (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 110     if true && (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 111     if true || (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 112
 113     let mut x = true;
 114     if x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 115     //~^ ERROR mismatched types
 116
 117     if true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 118     //~^ ERROR mismatched types
 119     if ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 120     //~^ ERROR mismatched types
 121     if (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
 122     //~^ ERROR mismatched types
 123
 124     // Binds as `(let ... = true)..true &&/|| false`.
 125     if let Range { start: _, end: _ } = true..true && false {}
 126     //~^ ERROR `let` expressions are not supported here
 127     //~| ERROR mismatched types
 128     //~| ERROR mismatched types
 129     if let Range { start: _, end: _ } = true..true || false {}
 130     //~^ ERROR `let` expressions are not supported here
 131     //~| ERROR mismatched types
 132     //~| ERROR mismatched types
 133
 134     // Binds as `(let Range { start: F, end } = F)..(|| true)`.
 135     const F: fn() -> bool = || true;
 136     if let Range { start: F, end } = F..|| true {}
 137     //~^ ERROR `let` expressions are not supported here
 138     //~| ERROR mismatched types
 139     //~| ERROR mismatched types
 140     //~| ERROR mismatched types
 141
 142     // Binds as `(let Range { start: true, end } = t)..(&&false)`.
 143     let t = &&true;
 144     if let Range { start: true, end } = t..&&false {}
 145     //~^ ERROR `let` expressions are not supported here
 146     //~| ERROR mismatched types
 147     //~| ERROR mismatched types
 148     //~| ERROR mismatched types
 149
 150     if let true = let true = true {} //~ ERROR `let` expressions are not supported here
 151 }
 152
 153 fn nested_within_while_expr() {
 154     while &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 155     //~^ ERROR mismatched types
 156
 157     while !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 158     while *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 159     //~^ ERROR type `bool` cannot be dereferenced
 160     while -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 161     //~^ ERROR cannot apply unary operator `-` to type `bool`
 162
 163     fn _check_try_binds_tighter() -> Result<(), ()> {
 164         while let 0 = 0? {}
 165         //~^ ERROR the `?` operator can only be applied to values that implement `Try`
 166         Ok(())
 167     }
 168     while (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
 169     //~^ ERROR the `?` operator can only be applied to values that implement `Try`
 170     //~| ERROR the `?` operator can only be used in a function that returns `Result`
 171
 172     while true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 173     while (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 174     while true && (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 175     while true || (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 176
 177     let mut x = true;
 178     while x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
 179     //~^ ERROR mismatched types
 180
 181     while true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 182     //~^ ERROR mismatched types
 183     while ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
 184     //~^ ERROR mismatched types
 185     while (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
 186     //~^ ERROR mismatched types
 187
 188     // Binds as `(let ... = true)..true &&/|| false`.
 189     while let Range { start: _, end: _ } = true..true && false {}
 190     //~^ ERROR `let` expressions are not supported here
 191     //~| ERROR mismatched types
 192     //~| ERROR mismatched types
 193     while let Range { start: _, end: _ } = true..true || false {}
 194     //~^ ERROR `let` expressions are not supported here
 195     //~| ERROR mismatched types
 196     //~| ERROR mismatched types
 197
 198     // Binds as `(let Range { start: F, end } = F)..(|| true)`.
 199     const F: fn() -> bool = || true;
 200     while let Range { start: F, end } = F..|| true {}
 201     //~^ ERROR `let` expressions are not supported here
 202     //~| ERROR mismatched types
 203     //~| ERROR mismatched types
 204     //~| ERROR mismatched types
 205
 206     // Binds as `(let Range { start: true, end } = t)..(&&false)`.
 207     let t = &&true;
 208     while let Range { start: true, end } = t..&&false {}
 209     //~^ ERROR `let` expressions are not supported here
 210     //~| ERROR mismatched types
 211     //~| ERROR mismatched types
 212     //~| ERROR mismatched types
 213
 214     while let true = let true = true {} //~ ERROR `let` expressions are not supported here
 215 }
 216
 217 fn not_error_because_clarified_intent() {
 218     if let Range { start: _, end: _ } = (true..true || false) { }
 219
 220     if let Range { start: _, end: _ } = (true..true && false) { }
 221
 222     while let Range { start: _, end: _ } = (true..true || false) { }
 223
 224     while let Range { start: _, end: _ } = (true..true && false) { }
 225 }
 226
 227 fn outside_if_and_while_expr() {
 228     &let 0 = 0; //~ ERROR `let` expressions are not supported here
 229
 230     !let 0 = 0; //~ ERROR `let` expressions are not supported here
 231     *let 0 = 0; //~ ERROR `let` expressions are not supported here
 232     //~^ ERROR type `bool` cannot be dereferenced
 233     -let 0 = 0; //~ ERROR `let` expressions are not supported here
 234     //~^ ERROR cannot apply unary operator `-` to type `bool`
 235
 236     fn _check_try_binds_tighter() -> Result<(), ()> {
 237         let 0 = 0?;
 238         //~^ ERROR the `?` operator can only be applied to values that implement `Try`
 239         Ok(())
 240     }
 241     (let 0 = 0)?; //~ ERROR `let` expressions are not supported here
 242     //~^ ERROR the `?` operator can only be used in a function that returns `Result`
 243     //~| ERROR the `?` operator can only be applied to values that implement `Try`
 244
 245     true || let 0 = 0; //~ ERROR `let` expressions are not supported here
 246     (true || let 0 = 0); //~ ERROR `let` expressions are not supported here
 247     true && (true || let 0 = 0); //~ ERROR `let` expressions are not supported here
 248
 249     let mut x = true;
 250     x = let 0 = 0; //~ ERROR `let` expressions are not supported here
 251
 252     true..(let 0 = 0); //~ ERROR `let` expressions are not supported here
 253     ..(let 0 = 0); //~ ERROR `let` expressions are not supported here
 254     (let 0 = 0)..; //~ ERROR `let` expressions are not supported here
 255
 256     (let Range { start: _, end: _ } = true..true || false);
 257     //~^ ERROR `let` expressions are not supported here
 258     //~| ERROR mismatched types
 259
 260     (let true = let true = true);
 261     //~^ ERROR `let` expressions are not supported here
 262
 263     // Check function tail position.
 264     &let 0 = 0
 265     //~^ ERROR `let` expressions are not supported here
 266     //~| ERROR mismatched types
 267 }
 268
 269 // Let's make sure that `let` inside const generic arguments are considered.
 270 fn inside_const_generic_arguments() {
 271     struct A<const B: bool>;
 272     impl<const B: bool> A<{B}> { const O: u32 = 5; }
 273
 274     if let A::<{
 275         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
 276     }>::O = 5 {}
 277
 278     while let A::<{
 279         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
 280     }>::O = 5 {}
 281
 282     if A::<{
 283         true && let 1 = 1 //~ ERROR `let` expressions are not supported here
 284     }>::O == 5 {}
 285
 286     // In the cases above we have `ExprKind::Block` to help us out.
 287     // Below however, we would not have a block and so an implementation might go
 288     // from visiting expressions to types without banning `let` expressions down the tree.
 289     // This tests ensures that we are not caught by surprise should the parser
 290     // admit non-IDENT expressions in const generic arguments.
 291
 292     if A::<
 293         true && let 1 = 1
 294         //~^ ERROR `let` expressions are not supported here
 295         //~| ERROR  expressions must be enclosed in braces
 296     >::O == 5 {}
 297 }
 298
 299 fn with_parenthesis() {
 300     let opt = Some(Some(1i32));
 301
 302     if (let Some(a) = opt && true) {
 303     //~^ ERROR `let` expressions are not supported here
 304     }
 305
 306     if (let Some(a) = opt) && true {
 307     //~^ ERROR `let` expressions are not supported here
 308     }
 309     if (let Some(a) = opt) && (let Some(b) = a) {
 310     //~^ ERROR `let` expressions are not supported here
 311     //~| ERROR `let` expressions are not supported here
 312     }
 313     if let Some(a) = opt && (true && true) {
 314     }
 315
 316     if (let Some(a) = opt && (let Some(b) = a)) && b == 1 {
 317     //~^ ERROR `let` expressions are not supported here
 318     //~| ERROR `let` expressions are not supported here
 319     }
 320     if (let Some(a) = opt && (let Some(b) = a)) && true {
 321     //~^ ERROR `let` expressions are not supported here
 322     //~| ERROR `let` expressions are not supported here
 323     }
 324     if (let Some(a) = opt && (true)) && true {
 325     //~^ ERROR `let` expressions are not supported here
 326     }
 327
 328     if (true && (true)) && let Some(a) = opt {
 329     }
 330     if (true) && let Some(a) = opt {
 331     }
 332     if true && let Some(a) = opt {
 333     }
 334
 335     let fun = || true;
 336     if let true = (true && fun()) && (true) {
 337     }
 338 }