Files
addr2line
adler
adler32
ahash
aho_corasick
angle
approx
backtrace
bitflags
blender
bytemuck
byteorder
case
cast_trait
cfg_if
chrono
color
color_quant
const_fn
crc32fast
crossbeam
crossbeam_channel
crossbeam_deque
crossbeam_epoch
crossbeam_queue
crossbeam_skiplist
crossbeam_utils
darling
darling_core
darling_macro
dds
deflate
densevec
derive_builder
derive_builder_core
dot
downcast_rs
dual_quat
either
erased_serde
failure
failure_derive
fixedbitset
float_cmp
fnv
freeimage
freeimage_sys
freetype
freetype_gl_sys
freetype_sys
freetypegl
futures
futures_channel
futures_core
futures_executor
futures_io
futures_macro
futures_sink
futures_task
futures_util
async_await
future
io
lock
sink
stream
task
fxhash
generational_arena
generic_array
getrandom
gif
gimli
glfw
glfw_sys
glin
glin_derive
glsl
half
harfbuzz
harfbuzz_ft_sys
harfbuzz_sys
hashbrown
human_sort
ident_case
image
indexmap
instant
itertools
itoa
jpeg_decoder
lazy_static
libc
libm
lock_api
log
lut_parser
matrixmultiply
memchr
memoffset
meshopt
miniz_oxide
monotonic_clock
mopa
mutiny_derive
na
nalgebra
base
geometry
linalg
ncollide3d
bounding_volume
interpolation
partitioning
pipeline
procedural
query
algorithms
closest_points
contact
distance
nonlinear_time_of_impact
point
proximity
ray
time_of_impact
visitors
shape
transformation
utils
nom
num_complex
num_cpus
num_integer
num_iter
num_rational
num_traits
numext_constructor
numext_fixed_uint
numext_fixed_uint_core
numext_fixed_uint_hack
object
once_cell
parking_lot
parking_lot_core
pathfinding
pennereq
petgraph
pin_project_lite
pin_utils
png
polygon2
ppv_lite86
proc_macro2
proc_macro_crate
proc_macro_hack
proc_macro_nested
quote
rand
rand_chacha
rand_core
rand_distr
raw_window_handle
rawpointer
rayon
rayon_core
rect_packer
regex
regex_syntax
retain_mut
rin
rin_app
rin_blender
rin_core
rin_gl
rin_graphics
rin_gui
rin_material
rin_math
rin_postpo
rin_scene
rin_util
rin_window
rinblender
rinecs
rinecs_derive
rinecs_derive_utils
ringui_derive
rustc_demangle
rusty_pool
ryu
scopeguard
seitan
seitan_derive
semver
semver_parser
serde
serde_derive
serde_json
shaderdata_derive
simba
slab
slice_of_array
slotmap
smallvec
std140_data
streaming_iterator
strsim
syn
synstructure
thiserror
thiserror_impl
thread_local
tiff
time
toml
typenum
unchecked_unwrap
unicode_xid
vec2
vec3
weezl
x11
zlib_sys
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
use proc_macro2::Span;
use std::ops::{Deref, DerefMut};
use syn;
use syn::spanned::Spanned;
use {
    FromDeriveInput, FromField, FromGenericParam, FromGenerics, FromMeta, FromTypeParam,
    FromVariant, Result,
};

/// A value and an associated position in source code. The main use case for this is
/// to preserve position information to emit warnings from proc macros. You can use
/// a `SpannedValue<T>` as a field in any struct that implements or derives any of
/// `darling`'s core traits.
///
/// To access the underlying value, use the struct's `Deref` implementation.
///
/// # Defaulting
/// This type is meant to be used in conjunction with attribute-extracted options,
/// but the user may not always explicitly set those options in their source code.
/// In this case, using `Default::default()` will create an instance which points
/// to `Span::call_site()`.
#[derive(Debug, Clone)]
pub struct SpannedValue<T> {
    value: T,
    span: Span,
}

impl<T> SpannedValue<T> {
    pub fn new(value: T, span: Span) -> Self {
        SpannedValue { value, span }
    }

    /// Get the source code location referenced by this struct.
    pub fn span(&self) -> Span {
        self.span
    }
}

impl<T: Default> Default for SpannedValue<T> {
    fn default() -> Self {
        SpannedValue::new(Default::default(), Span::call_site())
    }
}

impl<T> Deref for SpannedValue<T> {
    type Target = T;

    fn deref(&self) -> &T {
        &self.value
    }
}

impl<T> DerefMut for SpannedValue<T> {
    fn deref_mut(&mut self) -> &mut T {
        &mut self.value
    }
}

impl<T> AsRef<T> for SpannedValue<T> {
    fn as_ref(&self) -> &T {
        &self.value
    }
}

macro_rules! spanned {
    ($trayt:ident, $method:ident, $syn:path) => {
        impl<T: $trayt> $trayt for SpannedValue<T> {
            fn $method(value: &$syn) -> Result<Self> {
                Ok(SpannedValue::new(
                    $trayt::$method(value).map_err(|e| e.with_span(value))?,
                    value.span(),
                ))
            }
        }
    };
}

spanned!(FromGenericParam, from_generic_param, syn::GenericParam);
spanned!(FromGenerics, from_generics, syn::Generics);
spanned!(FromTypeParam, from_type_param, syn::TypeParam);
spanned!(FromMeta, from_meta, syn::Meta);
spanned!(FromDeriveInput, from_derive_input, syn::DeriveInput);
spanned!(FromField, from_field, syn::Field);
spanned!(FromVariant, from_variant, syn::Variant);

impl<T: Spanned> From<T> for SpannedValue<T> {
    fn from(value: T) -> Self {
        let span = value.span();
        SpannedValue::new(value, span)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use proc_macro2::Span;

    /// Make sure that `SpannedValue` can be seamlessly used as its underlying type.
    #[test]
    fn deref() {
        let test = SpannedValue::new("hello", Span::call_site());
        assert_eq!("hello", test.trim());
    }
}