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compiler-errors opened this issue Apr 18, 2025 · 3 comments · May be fixed by rust-lang/rust#140496
Open

calling impl Fn in defining scope #181

compiler-errors opened this issue Apr 18, 2025 · 3 comments · May be fixed by rust-lang/rust#140496
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from-crater A regression found via a crater run, not part of our test suite

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compiler-errors commented Apr 18, 2025 •
edited by lcnr
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impacts multiple crates:

struct ShExCompactPrinter;

struct TripleExpr;

impl ShExCompactPrinter {
    fn pp_triple_expr(&self) -> impl Fn(&TripleExpr, &ShExCompactPrinter) + '_ {
        move |te, printer| {
            printer.pp_triple_expr()(te, printer);
        }
    }
}
error[E0282]: type annotations needed
 --> /home/mgx/test.rs:8:13
  |
8 |             printer.pp_triple_expr()(te, printer);
  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type

error[E0618]: expected function, found `impl for<'a, 'b> Fn(&'a TripleExpr, &'b ShExCompactPrinter) + '_`
 --> /home/mgx/test.rs:8:13
  |
8 |             printer.pp_triple_expr()(te, printer);
  |             ^^^^^^^^^^^^^^^^^^^^^^^^-------------
  |             |
  |             call expression requires function

Has to do with recursive definition of opaque.
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@lcnr lcnr added the from-crater A regression found via a crater run, not part of our test suite label Apr 19, 2025
@lcnr lcnr changed the title shex_compact regression calling impl Fn in defining scope Apr 25, 2025
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lcnr commented Apr 29, 2025 •
edited
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fn foo() -> impl FnMut() -> usize {
    if false {
        let mut f = foo();
        f();
    }
    
    let mut state = 0;
    move || {
        state += 1;
        state
    }
}

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lcnr commented Apr 29, 2025 

fn foo() -> impl FnOnce() {
    if false {
        let mut f = foo();
        f();
    }
    
    let string = String::new();
    move || drop(string)
}

@lcnr lcnr moved this from unknown to todo in -Znext-solver=globally Apr 29, 2025
@compiler-errors compiler-errors linked a pull request Apr 30, 2025 that will close this issue
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@lcnr lcnr moved this from todo to in progress in -Znext-solver=globally Apr 30, 2025
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from-crater A regression found via a crater run, not part of our test suite
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