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Nested maps don't compile #183

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piegamesde opened this issue Oct 25, 2019 · 3 comments · May be fixed by #242
Open

Nested maps don't compile #183

piegamesde opened this issue Oct 25, 2019 · 3 comments · May be fixed by #242
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A-macros Area: phf-macros C-enhancement

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@piegamesde
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let map = phf_map!{
	"foo" => phf_map!{"k"=>"v"}
};

Compile error:

error[E0659]: `proc_macro_call` is ambiguous (macro-expanded name vs less macro-expanded name from outer scope during import/macro resolution)
  --> src/main.rs:57:12
   |
57 |       let map = phf_map!{
   |  _______________^
58 | |         "foo" => phf_map!{"k"=>"v"}
59 | |     };
   | |_____^ ambiguous name
   |
note: `proc_macro_call` could refer to the macro defined here
  --> src/main.rs:57:12
   |
57 |       let map = phf_map!{
   |  _______________^
58 | |         "foo" => phf_map!{"k"=>"v"}
59 | |     };
   | |_____^
note: `proc_macro_call` could also refer to the macro defined here
  --> src/main.rs:57:12
   |
57 |       let map = phf_map!{
   |  _______________^
58 | |         "foo" => phf_map!{"k"=>"v"}
59 | |     };
   | |_____^
   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
@x10an14
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x10an14 commented Mar 29, 2020

This is a desired feature for me too, until Rustlang decides whether to implement BTree or HashMap map! macro...

@stephanemagnenat
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I stumbled upon this limitation as well. This should at least be documented, so that a potential user of this crate does not invest a lot of time (e.g. to write a code generator for recursive phf data structures) before realising this is not supported.

@stephanemagnenat stephanemagnenat mentioned this issue Mar 24, 2021
Open
@JohnTitor JohnTitor added A-macros Area: phf-macros C-enhancement labels Jun 17, 2021
@Darksonn
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For anyone who runs in to this, note that this compiles just fine:

use phf::phf_map;

type InnerMap = phf::Map<&'static str, Option<&'static str>>;

static INNER1: InnerMap = phf_map! {
    "foo" => None,
    "bar" => Some("abc"),
};
static INNER2: InnerMap = phf_map! {
    "baz" => None,
    "bar" => Some("abc"),
};

static MY_MAP: phf::Map<&'static str, &'static InnerMap> = phf_map! {
    "hello" => &INNER1,
    "world" => &INNER2,
};

@vbe0201 vbe0201 linked a pull request Oct 22, 2021 that will close this issue
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A-macros Area: phf-macros C-enhancement
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Constify the code generator vbe0201/rust-phf
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@stephanemagnenat @x10an14 @Darksonn @piegamesde @JohnTitor