[rustc.git] / src / test / ui / rfc-2497-if-let-chains / disallowed-positions.rs

// Here we test that `lowering` behaves correctly wrt. `let $pats = $expr` expressions.
//
// We want to make sure that `let` is banned in situations other than:
//
// expr =
//   | ...
//   | "if" expr_with_let block {"else" block}?
//   | {label ":"}? while" expr_with_let block
//   ;
//
// expr_with_let =
//   | "let" top_pats "=" expr
//   | expr_with_let "&&" expr_with_let
//   | "(" expr_with_let ")"
//   | expr
//   ;
//
// To that end, we check some positions which is not part of the language above.

#![feature(const_generics)]
//~^ WARN the feature `const_generics` is incomplete
#![feature(let_chains)] // Avoid inflating `.stderr` with overzealous gates in this test.
//~^ WARN the feature `let_chains` is incomplete

#![allow(irrefutable_let_patterns)]

use std::ops::Range;

fn main() {}

fn nested_within_if_expr() {
    if &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    if !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    if *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR type `bool` cannot be dereferenced
    if -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR cannot apply unary operator `-` to type `bool`

    fn _check_try_binds_tighter() -> Result<(), ()> {
        if let 0 = 0? {}
        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
        Ok(())
    }
    if (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
    //~| ERROR the `?` operator can only be used in a function that returns `Result`

    if true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    if (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    if true && (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    if true || (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here

    let mut x = true;
    if x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    if true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types
    if ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types
    if (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    // Binds as `(let ... = true)..true &&/|| false`.
    if let Range { start: _, end: _ } = true..true && false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    if let Range { start: _, end: _ } = true..true || false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    // Binds as `(let Range { start: F, end } = F)..(|| true)`.
    const F: fn() -> bool = || true;
    if let Range { start: F, end } = F..|| true {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    // Binds as `(let Range { start: true, end } = t)..(&&false)`.
    let t = &&true;
    if let Range { start: true, end } = t..&&false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    if let true = let true = true {} //~ ERROR `let` expressions are not supported here
}

fn nested_within_while_expr() {
    while &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    while !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    while *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR type `bool` cannot be dereferenced
    while -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR cannot apply unary operator `-` to type `bool`

    fn _check_try_binds_tighter() -> Result<(), ()> {
        while let 0 = 0? {}
        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
        Ok(())
    }
    while (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
    //~| ERROR the `?` operator can only be used in a function that returns `Result`

    while true || let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    while (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    while true && (true || let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    while true || (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here

    let mut x = true;
    while x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    while true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types
    while ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types
    while (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
    //~^ ERROR mismatched types

    // Binds as `(let ... = true)..true &&/|| false`.
    while let Range { start: _, end: _ } = true..true && false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    while let Range { start: _, end: _ } = true..true || false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    // Binds as `(let Range { start: F, end } = F)..(|| true)`.
    const F: fn() -> bool = || true;
    while let Range { start: F, end } = F..|| true {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    // Binds as `(let Range { start: true, end } = t)..(&&false)`.
    let t = &&true;
    while let Range { start: true, end } = t..&&false {}
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
    //~| ERROR mismatched types
    //~| ERROR mismatched types

    while let true = let true = true {} //~ ERROR `let` expressions are not supported here
}

fn not_error_because_clarified_intent() {
    if let Range { start: _, end: _ } = (true..true || false) { }

    if let Range { start: _, end: _ } = (true..true && false) { }

    while let Range { start: _, end: _ } = (true..true || false) { }

    while let Range { start: _, end: _ } = (true..true && false) { }
}

fn outside_if_and_while_expr() {
    &let 0 = 0; //~ ERROR `let` expressions are not supported here

    !let 0 = 0; //~ ERROR `let` expressions are not supported here
    *let 0 = 0; //~ ERROR `let` expressions are not supported here
    //~^ ERROR type `bool` cannot be dereferenced
    -let 0 = 0; //~ ERROR `let` expressions are not supported here
    //~^ ERROR cannot apply unary operator `-` to type `bool`

    fn _check_try_binds_tighter() -> Result<(), ()> {
        let 0 = 0?;
        //~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
        Ok(())
    }
    (let 0 = 0)?; //~ ERROR `let` expressions are not supported here
    //~^ ERROR the `?` operator can only be used in a function that returns `Result`
    //~| ERROR the `?` operator can only be applied to values that implement `std::ops::Try`

    true || let 0 = 0; //~ ERROR `let` expressions are not supported here
    (true || let 0 = 0); //~ ERROR `let` expressions are not supported here
    true && (true || let 0 = 0); //~ ERROR `let` expressions are not supported here

    let mut x = true;
    x = let 0 = 0; //~ ERROR `let` expressions are not supported here

    true..(let 0 = 0); //~ ERROR `let` expressions are not supported here
    ..(let 0 = 0); //~ ERROR `let` expressions are not supported here
    (let 0 = 0)..; //~ ERROR `let` expressions are not supported here

    (let Range { start: _, end: _ } = true..true || false);
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types

    (let true = let true = true);
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR `let` expressions are not supported here

    // Check function tail position.
    &let 0 = 0
    //~^ ERROR `let` expressions are not supported here
    //~| ERROR mismatched types
}

// Let's make sure that `let` inside const generic arguments are considered.
fn inside_const_generic_arguments() {
    struct A<const B: bool>;
    impl<const B: bool> A<{B}> { const O: u32 = 5; }

    if let A::<{
        true && let 1 = 1 //~ ERROR `let` expressions are not supported here
        //~| ERROR `match` is not allowed in a `const`
    }>::O = 5 {}

    while let A::<{
        true && let 1 = 1 //~ ERROR `let` expressions are not supported here
        //~| ERROR `match` is not allowed in a `const`
    }>::O = 5 {}

    if A::<{
        true && let 1 = 1 //~ ERROR `let` expressions are not supported here
        //~| ERROR `match` is not allowed in a `const`
    }>::O == 5 {}

    // In the cases above we have `ExprKind::Block` to help us out.
    // Below however, we would not have a block and so an implementation might go
    // from visiting expressions to types without banning `let` expressions down the tree.
    // This tests ensures that we are not caught by surprise should the parser
    // admit non-IDENT expressions in const generic arguments.

    if A::<
        true && let 1 = 1 //~ ERROR expected one of `,` or `>`, found `&&`
    >::O == 5 {}
}
Commit	Line	Data
dc9dc135 XL	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(const_generics)]
	21	//~^ WARN the feature `const_generics` is incomplete
	22	#![feature(let_chains)] // Avoid inflating `.stderr` with overzealous gates in this test.
	23	//~^ WARN the feature `let_chains` is incomplete
	24
	25	#![allow(irrefutable_let_patterns)]
	26
	27	use std::ops::Range;
	28
	29	fn main() {}
	30
	31	fn nested_within_if_expr() {
	32	if &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	33	//~^ ERROR mismatched types
	34
	35	if !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	36	if *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	37	//~^ ERROR type `bool` cannot be dereferenced
	38	if -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	39	//~^ ERROR cannot apply unary operator `-` to type `bool`
	40
	41	fn _check_try_binds_tighter() -> Result<(), ()> {
	42	if let 0 = 0? {}
	43	//~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
	44	Ok(())
	45	}
	46	if (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
	47	//~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
	48	//~\| ERROR the `?` operator can only be used in a function that returns `Result`
	49
	50	if true \|\| let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	51	if (true \|\| let 0 = 0) {} //~ ERROR `let` expressions are not supported here
	52	if true && (true \|\| let 0 = 0) {} //~ ERROR `let` expressions are not supported here
	53	if true \|\| (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here
	54
	55	let mut x = true;
	56	if x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
	57	//~^ ERROR mismatched types
	58
	59	if true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
	60	//~^ ERROR mismatched types
	61	if ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
	62	//~^ ERROR mismatched types
	63	if (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
	64	//~^ ERROR mismatched types
65
66	// Binds as `(let ... = true)..true &&/\|\| false`.
67	if let Range { start: _, end: _ } = true..true && false {}
68	//~^ ERROR `let` expressions are not supported here
69	//~\| ERROR mismatched types
70	//~\| ERROR mismatched types
71	if let Range { start: _, end: _ } = true..true \|\| false {}
72	//~^ ERROR `let` expressions are not supported here
73	//~\| ERROR mismatched types
74	//~\| ERROR mismatched types
75
76	// Binds as `(let Range { start: F, end } = F)..(\|\| true)`.
77	const F: fn() -> bool = \|\| true;
78	if let Range { start: F, end } = F..\|\| true {}
79	//~^ ERROR `let` expressions are not supported here
80	//~\| ERROR mismatched types
81	//~\| ERROR mismatched types
82	//~\| ERROR mismatched types
83
84	// Binds as `(let Range { start: true, end } = t)..(&&false)`.
85	let t = &&true;
86	if let Range { start: true, end } = t..&&false {}
87	//~^ ERROR `let` expressions are not supported here
88	//~\| ERROR mismatched types
89	//~\| ERROR mismatched types
90	//~\| ERROR mismatched types
91
92	if let true = let true = true {} //~ ERROR `let` expressions are not supported here
93	}
94
95	fn nested_within_while_expr() {
96	while &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
97	//~^ ERROR mismatched types
98
99	while !let 0 = 0 {} //~ ERROR `let` expressions are not supported here
100	while *let 0 = 0 {} //~ ERROR `let` expressions are not supported here
101	//~^ ERROR type `bool` cannot be dereferenced
102	while -let 0 = 0 {} //~ ERROR `let` expressions are not supported here
103	//~^ ERROR cannot apply unary operator `-` to type `bool`
104
105	fn _check_try_binds_tighter() -> Result<(), ()> {
106	while let 0 = 0? {}
107	//~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
108	Ok(())
109	}
110	while (let 0 = 0)? {} //~ ERROR `let` expressions are not supported here
111	//~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
112	//~\| ERROR the `?` operator can only be used in a function that returns `Result`
113
114	while true \|\| let 0 = 0 {} //~ ERROR `let` expressions are not supported here
115	while (true \|\| let 0 = 0) {} //~ ERROR `let` expressions are not supported here
116	while true && (true \|\| let 0 = 0) {} //~ ERROR `let` expressions are not supported here
117	while true \|\| (true && let 0 = 0) {} //~ ERROR `let` expressions are not supported here
118
119	let mut x = true;
120	while x = let 0 = 0 {} //~ ERROR `let` expressions are not supported here
121	//~^ ERROR mismatched types
122
123	while true..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
124	//~^ ERROR mismatched types
125	while ..(let 0 = 0) {} //~ ERROR `let` expressions are not supported here
126	//~^ ERROR mismatched types
127	while (let 0 = 0).. {} //~ ERROR `let` expressions are not supported here
128	//~^ ERROR mismatched types
129
130	// Binds as `(let ... = true)..true &&/\|\| false`.
131	while let Range { start: _, end: _ } = true..true && false {}
132	//~^ ERROR `let` expressions are not supported here
133	//~\| ERROR mismatched types
134	//~\| ERROR mismatched types
135	while let Range { start: _, end: _ } = true..true \|\| false {}
136	//~^ ERROR `let` expressions are not supported here
137	//~\| ERROR mismatched types
138	//~\| ERROR mismatched types
139
140	// Binds as `(let Range { start: F, end } = F)..(\|\| true)`.
141	const F: fn() -> bool = \|\| true;
142	while let Range { start: F, end } = F..\|\| true {}
143	//~^ ERROR `let` expressions are not supported here
144	//~\| ERROR mismatched types
145	//~\| ERROR mismatched types
146	//~\| ERROR mismatched types
147
148	// Binds as `(let Range { start: true, end } = t)..(&&false)`.
149	let t = &&true;
150	while let Range { start: true, end } = t..&&false {}
151	//~^ ERROR `let` expressions are not supported here
152	//~\| ERROR mismatched types
153	//~\| ERROR mismatched types
154	//~\| ERROR mismatched types
155
156	while let true = let true = true {} //~ ERROR `let` expressions are not supported here
157	}
158
159	fn not_error_because_clarified_intent() {
160	if let Range { start: _, end: _ } = (true..true \|\| false) { }
161
162	if let Range { start: _, end: _ } = (true..true && false) { }
163
164	while let Range { start: _, end: _ } = (true..true \|\| false) { }
165
166	while let Range { start: _, end: _ } = (true..true && false) { }
167	}
168
169	fn outside_if_and_while_expr() {
170	&let 0 = 0; //~ ERROR `let` expressions are not supported here
171
172	!let 0 = 0; //~ ERROR `let` expressions are not supported here
173	*let 0 = 0; //~ ERROR `let` expressions are not supported here
174	//~^ ERROR type `bool` cannot be dereferenced
175	-let 0 = 0; //~ ERROR `let` expressions are not supported here
176	//~^ ERROR cannot apply unary operator `-` to type `bool`
177
178	fn _check_try_binds_tighter() -> Result<(), ()> {
179	let 0 = 0?;
180	//~^ ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
181	Ok(())
182	}
183	(let 0 = 0)?; //~ ERROR `let` expressions are not supported here
184	//~^ ERROR the `?` operator can only be used in a function that returns `Result`
185	//~\| ERROR the `?` operator can only be applied to values that implement `std::ops::Try`
186
187	true \|\| let 0 = 0; //~ ERROR `let` expressions are not supported here
188	(true \|\| let 0 = 0); //~ ERROR `let` expressions are not supported here
189	true && (true \|\| let 0 = 0); //~ ERROR `let` expressions are not supported here
190
191	let mut x = true;
192	x = let 0 = 0; //~ ERROR `let` expressions are not supported here
193
194	true..(let 0 = 0); //~ ERROR `let` expressions are not supported here
195	..(let 0 = 0); //~ ERROR `let` expressions are not supported here
196	(let 0 = 0)..; //~ ERROR `let` expressions are not supported here
197
198	(let Range { start: _, end: _ } = true..true \|\| false);
199	//~^ ERROR `let` expressions are not supported here
200	//~\| ERROR mismatched types
201
202	(let true = let true = true);
203	//~^ ERROR `let` expressions are not supported here
204	//~\| ERROR `let` expressions are not supported here
205
206	// Check function tail position.
207	&let 0 = 0
208	//~^ ERROR `let` expressions are not supported here
209	//~\| ERROR mismatched types
210	}
211
212	// Let's make sure that `let` inside const generic arguments are considered.
213	fn inside_const_generic_arguments() {
214	struct A<const B: bool>;
215	impl<const B: bool> A<{B}> { const O: u32 = 5; }
216
217	if let A::<{
218	true && let 1 = 1 //~ ERROR `let` expressions are not supported here
60c5eb7d	219	//~\| ERROR `match` is not allowed in a `const`
dc9dc135 XL	220	}>::O = 5 {}
	221
	222	while let A::<{
	223	true && let 1 = 1 //~ ERROR `let` expressions are not supported here
60c5eb7d	224	//~\| ERROR `match` is not allowed in a `const`
dc9dc135 XL	225	}>::O = 5 {}
	226
	227	if A::<{
	228	true && let 1 = 1 //~ ERROR `let` expressions are not supported here
60c5eb7d	229	//~\| ERROR `match` is not allowed in a `const`
dc9dc135 XL	230	}>::O == 5 {}
	231
	232	// In the cases above we have `ExprKind::Block` to help us out.
	233	// Below however, we would not have a block and so an implementation might go
	234	// from visiting expressions to types without banning `let` expressions down the tree.
	235	// This tests ensures that we are not caught by surprise should the parser
	236	// admit non-IDENT expressions in const generic arguments.
	237
	238	if A::<
	239	true && let 1 = 1 //~ ERROR expected one of `,` or `>`, found `&&`
	240	>::O == 5 {}
	241	}