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Merged
rust-bors merged 2 commits into from
Aug 3, 2026
+205 −52
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Improve the test for patterns in fn pointers #160380

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32ba9ca
Improve the layout of the test
JonathanBrouwer Aug 2, 2026
c25abc5
Test syntax of patterns in fn ptrs
JonathanBrouwer Aug 2, 2026
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73 changes: 62 additions & 11 deletions tests/ui/fn/fn-ptr-pattern.rs
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Original file line number Diff line number Diff line change
@@ -1,26 +1,77 @@
fn patterns<F>(
pat1: fn(true: bool),
fn allowed<F>(
data: &str,
f1: fn(msg: String),
f2: fn(_: String),
f3: fn(String, msg: String),
f4: fn(msg: String, String),
f5: fn(duplicate_name: bool, duplicate_name: bool),
) { }


// Patterns are semantically rejected
fn semantics<F>(
pat1: fn(1..3: bool),
//~^ ERROR patterns aren't allowed in function pointer types
pat2: fn(1..3: bool),
pat2: fn((x, y): (bool, bool)),
//~^ ERROR patterns aren't allowed in function pointer types
pat3: fn((x, y): (bool, bool)),
pat3: fn(Thing { a, b }: Thing),
//~^ ERROR patterns aren't allowed in function pointer types
pat4: fn(NoThing { a, b }: NoThing),
//~^ ERROR patterns aren't allowed in function pointer types
//~| ERROR cannot find type `NoThing` in this scope
pat5: fn((((((x))))): bool),
//~^ ERROR patterns aren't allowed in function pointer types
pat4: fn(self),

self1: fn(self),
//~^ ERROR `self` parameter is only allowed in associated functions
pat5: fn(self, self),
self2: fn(self, self),
//~^ ERROR `self` parameter is only allowed in associated functions
//~| ERROR unexpected `self` parameter in function
pat6: fn(bool, self),
self3: fn(bool, self),
//~^ ERROR unexpected `self` parameter in function
pat7: fn(Thing { a, b }: Thing),

restricted_pat1: fn(mut x: ()),
//~^ ERROR patterns aren't allowed in function pointer types
pat8: fn(NoThing { a, b }: NoThing),
restricted_pat2: fn(&x: ()),
//~^ ERROR patterns aren't allowed in function pointer types
//~| ERROR cannot find type `NoThing` in this scope
pat9: fn((((((x))))): bool),
restricted_pat3: fn(&&x: ()),
//~^ ERROR patterns aren't allowed in function pointer types
restricted_pat4: fn(false: ()),
//~^ ERROR patterns aren't allowed in function pointer types
restricted_pat5: fn(&_: ()),
//~^ ERROR patterns aren't allowed in function pointer types
restricted_pat6: fn(&true: ()),
//~^ ERROR patterns aren't allowed in function pointer types
) { }

// Patterns are also syntactically rejected, but restricted patterns are not
#[cfg(false)]
fn syntax<F>(
pat1: fn(1..3: bool),
//~^ ERROR patterns aren't allowed in function pointer types
pat2: fn((x, y): (bool, bool)),
//~^ ERROR patterns aren't allowed in function pointer types
pat3: fn(Thing { a, b }: Thing),
//~^ ERROR patterns aren't allowed in function pointer types
pat4: fn(NoThing { a, b }: NoThing),
//~^ ERROR patterns aren't allowed in function pointer types
pat5: fn((((((x))))): bool),
//~^ ERROR patterns aren't allowed in function pointer types

self1: fn(self),
self2: fn(self, self),
//~^ ERROR unexpected `self` parameter in function
self3: fn(bool, self),
//~^ ERROR unexpected `self` parameter in function

restricted_pat1: fn(mut x: ()),
restricted_pat2: fn(&x: ()),
restricted_pat3: fn(&&x: ()),
restricted_pat4: fn(false: ()),
restricted_pat5: fn(&_: ()),
restricted_pat6: fn(&true: ()),
) { }

struct Thing { a: bool, b: bool }

fn main() {
Expand Down
184 changes: 143 additions & 41 deletions tests/ui/fn/fn-ptr-pattern.stderr
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Original file line number Diff line number Diff line change
@@ -1,113 +1,215 @@
error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:4:14
--> $DIR/fn-ptr-pattern.rs:13:14
|
LL | pat2: fn(1..3: bool),
LL | pat1: fn(1..3: bool),
| ^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat2: fn(1..3: bool),
LL + pat2: fn(_: bool),
LL - pat1: fn(1..3: bool),
LL + pat1: fn(_: bool),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:6:14
--> $DIR/fn-ptr-pattern.rs:15:14
|
LL | pat3: fn((x, y): (bool, bool)),
LL | pat2: fn((x, y): (bool, bool)),
| ^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat3: fn((x, y): (bool, bool)),
LL + pat3: fn(_: (bool, bool)),
LL - pat2: fn((x, y): (bool, bool)),
LL + pat2: fn(_: (bool, bool)),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:17:14
|
LL | pat3: fn(Thing { a, b }: Thing),
| ^^^^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat3: fn(Thing { a, b }: Thing),
LL + pat3: fn(_: Thing),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:19:14
|
LL | pat4: fn(NoThing { a, b }: NoThing),
| ^^^^^^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat4: fn(NoThing { a, b }: NoThing),
LL + pat4: fn(_: NoThing),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:22:14
|
LL | pat5: fn((((((x))))): bool),
| ^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat5: fn((((((x))))): bool),
LL + pat5: fn(_: bool),
|

error: unexpected `self` parameter in function
--> $DIR/fn-ptr-pattern.rs:10:20
--> $DIR/fn-ptr-pattern.rs:27:21
|
LL | pat5: fn(self, self),
| ^^^^ must be the first parameter of an associated function
LL | self2: fn(self, self),
| ^^^^ must be the first parameter of an associated function

error: unexpected `self` parameter in function
--> $DIR/fn-ptr-pattern.rs:13:20
--> $DIR/fn-ptr-pattern.rs:30:21
|
LL | pat6: fn(bool, self),
| ^^^^ must be the first parameter of an associated function
LL | self3: fn(bool, self),
| ^^^^ must be the first parameter of an associated function

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:15:14
--> $DIR/fn-ptr-pattern.rs:50:14
|
LL | pat1: fn(1..3: bool),
| ^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat1: fn(1..3: bool),
LL + pat1: fn(_: bool),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:52:14
|
LL | pat2: fn((x, y): (bool, bool)),
| ^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat2: fn((x, y): (bool, bool)),
LL + pat2: fn(_: (bool, bool)),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:54:14
|
LL | pat7: fn(Thing { a, b }: Thing),
LL | pat3: fn(Thing { a, b }: Thing),
| ^^^^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat7: fn(Thing { a, b }: Thing),
LL + pat7: fn(_: Thing),
LL - pat3: fn(Thing { a, b }: Thing),
LL + pat3: fn(_: Thing),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:17:14
--> $DIR/fn-ptr-pattern.rs:56:14
|
LL | pat8: fn(NoThing { a, b }: NoThing),
LL | pat4: fn(NoThing { a, b }: NoThing),
| ^^^^^^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat8: fn(NoThing { a, b }: NoThing),
LL + pat8: fn(_: NoThing),
LL - pat4: fn(NoThing { a, b }: NoThing),
LL + pat4: fn(_: NoThing),
|

error[E0642]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:20:14
--> $DIR/fn-ptr-pattern.rs:58:14
|
LL | pat9: fn((((((x))))): bool),
LL | pat5: fn((((((x))))): bool),
| ^^^^^^^^^^^
|
help: give this argument a name or use an underscore to ignore it
|
LL - pat9: fn((((((x))))): bool),
LL + pat9: fn(_: bool),
LL - pat5: fn((((((x))))): bool),
LL + pat5: fn(_: bool),
|

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:2:14
error: unexpected `self` parameter in function
--> $DIR/fn-ptr-pattern.rs:62:21
|
LL | pat1: fn(true: bool),
| ^^^^
LL | self2: fn(self, self),
| ^^^^ must be the first parameter of an associated function

error: unexpected `self` parameter in function
--> $DIR/fn-ptr-pattern.rs:64:21
|
LL | self3: fn(bool, self),
| ^^^^ must be the first parameter of an associated function

error: `self` parameter is only allowed in associated functions
--> $DIR/fn-ptr-pattern.rs:8:14
--> $DIR/fn-ptr-pattern.rs:25:15
|
LL | pat4: fn(self),
| ^^^^ not semantically valid as function parameter
LL | self1: fn(self),
| ^^^^ not semantically valid as function parameter
|
= note: associated functions are those in `impl` or `trait` definitions

error: `self` parameter is only allowed in associated functions
--> $DIR/fn-ptr-pattern.rs:10:14
--> $DIR/fn-ptr-pattern.rs:27:15
|
LL | pat5: fn(self, self),
| ^^^^ not semantically valid as function parameter
LL | self2: fn(self, self),
| ^^^^ not semantically valid as function parameter
|
= note: associated functions are those in `impl` or `trait` definitions

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:33:25
|
LL | restricted_pat1: fn(mut x: ()),
| ^^^^^

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:35:25
|
LL | restricted_pat2: fn(&x: ()),
| ^^

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:37:25
|
LL | restricted_pat3: fn(&&x: ()),
| ^^^

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:39:25
|
LL | restricted_pat4: fn(false: ()),
| ^^^^^

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:41:25
|
LL | restricted_pat5: fn(&_: ()),
| ^^

error[E0561]: patterns aren't allowed in function pointer types
--> $DIR/fn-ptr-pattern.rs:43:25
|
LL | restricted_pat6: fn(&true: ()),
| ^^^^^

error[E0425]: cannot find type `NoThing` in this scope
--> $DIR/fn-ptr-pattern.rs:17:32
--> $DIR/fn-ptr-pattern.rs:19:32
|
LL | pat8: fn(NoThing { a, b }: NoThing),
LL | pat4: fn(NoThing { a, b }: NoThing),
| ^^^^^^^
...
LL | struct Thing { a: bool, b: bool }
| ------------ similarly named struct `Thing` defined here
|
help: a struct with a similar name exists
|
LL - pat8: fn(NoThing { a, b }: NoThing),
LL + pat8: fn(NoThing { a, b }: Thing),
LL - pat4: fn(NoThing { a, b }: NoThing),
LL + pat4: fn(NoThing { a, b }: Thing),
|

error: aborting due to 11 previous errors
error: aborting due to 23 previous errors

Some errors have detailed explanations: E0425, E0561, E0642.
For more information about an error, try `rustc --explain E0425`.
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