Provide better span for diagnostics

internal/src/init.rs

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Apache-2.0 OR MIT
 
 use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote, ToTokens, TokenStreamExt};
+use quote::{format_ident, quote, quote_spanned, ToTokens, TokenStreamExt};
 use syn::{
     braced, parenthesized,
     parse::{End, Parse},
@@ -269,7 +269,6 @@ fn expand(
         },
         |(_, err)| Box::new(err),
     );
-    let slot = format_ident!("slot");
     let (has_data_trait, get_data, init_from_closure) = if pinned {
         (
             format_ident!("HasPinData"),
@@ -286,7 +285,7 @@ fn expand(
     let init_kind = get_init_kind(rest, dcx);
     let zeroable_check = match init_kind {
         InitKind::Normal => quote!(),
-        InitKind::Zeroing => quote! {
+        InitKind::Zeroing => quote_spanned! { Span::mixed_site() =>
             // The user specified `..Zeroable::zeroed()` at the end of the list of fields.
             // Therefore we check if the struct implements `Zeroable` and then zero the memory.
             // This allows us to also remove the check that all fields are present (since we
@@ -295,34 +294,33 @@ fn expand(
             where T: ::pin_init::Zeroable
             {}
             // Ensure that the struct is indeed `Zeroable`.
-            assert_zeroable(#slot);
+            assert_zeroable(slot);
             // SAFETY: The type implements `Zeroable` by the check above.
-            unsafe { ::core::ptr::write_bytes(#slot, 0, 1) };
+            unsafe { ::core::ptr::write_bytes(slot, 0, 1) };
         },
     };
     let this = match this {
         None => quote!(),
-        Some(This { ident, .. }) => quote! {
+        Some(This { ident, .. }) => quote_spanned! { Span::mixed_site() =>
             // Create the `this` so it can be referenced by the user inside of the
             // expressions creating the individual fields.
             let #ident = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };
         },
     };
     // `mixed_site` ensures that the data is not accessible to the user-controlled code.
-    let data = Ident::new("__data", Span::mixed_site());
-    let init_fields = init_fields(&fields, pinned, &data, &slot);
+    let init_fields = init_fields(&fields, pinned);
     let field_check = make_field_check(&fields, init_kind, &path);
-    Ok(quote! {{
+    Ok(quote_spanned! { Span::mixed_site() => {
         // Get the data about fields from the supplied type.
         // SAFETY: TODO
-        let #data = unsafe {
+        let data = unsafe {
             use ::pin_init::__internal::#has_data_trait;
             // Can't use `<#path as #has_data_trait>::#get_data`, since the user is able to omit
             // generics (which need to be present with that syntax).
             #path::#get_data()
         };
-        // Ensure that `#data` really is of type `#data` and help with type inference:
-        let init = #data.__make_closure::<_, #error>(
+        // Ensure that `data` really is of type `data` and help with type inference:
+        let init = data.__make_closure::<_, #error>(
             move |slot| {
                 #zeroable_check
                 #this
@@ -380,12 +378,7 @@ fn get_init_kind(rest: Option<(Token![..], Expr)>, dcx: &mut DiagCtxt) -> InitKi
 }
 
 /// Generate the code that initializes the fields of the struct using the initializers in `field`.
-fn init_fields(
-    fields: &Punctuated<InitializerField, Token![,]>,
-    pinned: bool,
-    data: &Ident,
-    slot: &Ident,
-) -> TokenStream {
+fn init_fields(fields: &Punctuated<InitializerField, Token![,]>, pinned: bool) -> TokenStream {
     let mut guards = vec![];
     let mut guard_attrs = vec![];
     let mut res = TokenStream::new();
@@ -411,18 +404,19 @@ fn init_fields(
             }
         };
         let ident = member.as_ident();
+        let span = Span::mixed_site().located_at(ident.span());
 
         let slot = if pinned {
-            quote! {
+            quote_spanned! { span =>
                 // SAFETY:
                 // - `slot` is valid and properly aligned.
                 // - `make_field_check` checks that `&raw mut (*slot).#member` is properly aligned.
                 // - `make_field_check` prevents `#member` from being used twice, therefore
                 //   `(*slot).#member` is exclusively accessed and has not been initialized.
-                (unsafe { #data.#ident(#slot) })
+                (unsafe { data.#ident(slot) })
             }
         } else {
-            quote! {
+            quote_spanned! { span =>
                 // For `init!()` macro, everything is unpinned.
                 // SAFETY:
                 // - `&raw mut (*slot).#member` is valid.
@@ -431,14 +425,15 @@ fn init_fields(
                 //   `(*slot).#member` is exclusively accessed and has not been initialized.
                 (unsafe {
                     ::pin_init::__internal::Slot::<::pin_init::__internal::Unpinned, _>::new(
-                        &raw mut (*#slot).#member
+                        &raw mut (*slot).#member
                     )
                 })
             }
         };
 
         // `mixed_site` ensures that the guard is not accessible to the user-controlled code.
         let guard = format_ident!("__{ident}_guard", span = Span::mixed_site());
+        let full_span = kind.span();
 
         let init = match kind {
             InitializerKind::Value { value, .. } => {
@@ -447,14 +442,13 @@ fn init_fields(
                     .map(|(_, value)| quote!(#value))
                     .unwrap_or_else(|| quote!(#member));
 
-                quote! {
+                quote_spanned! { full_span =>
                     #(#attrs)*
                     let mut #guard = #slot.write(#value);
-
                 }
             }
             InitializerKind::Init { value, .. } => {
-                quote! {
+                quote_spanned! { full_span =>
                     #(#attrs)*
                     let mut #guard = #slot.init(#value)?;
                 }
@@ -465,7 +459,7 @@ fn init_fields(
         // A tuple field has no name that could be bound here (the `_0` identifiers are considered
         // implementation detail and not user-facing).
         let binding = match member {
-            Member::Named(ident) => quote! {
+            Member::Named(ident) => quote_spanned! { span =>
                 #(#cfgs)*
                 // Allow `non_snake_case` since the same warning is going to be reported for the
                 // struct field.
@@ -512,7 +506,7 @@ fn make_field_check(
             ..::core::mem::zeroed()
         }),
     };
-    quote! {
+    quote_spanned! { Span::mixed_site() =>
         #[allow(unreachable_code)]
         // We use unreachable code to perform field checks. They're still checked by the compiler.
         // SAFETY: this code is never executed.

internal/src/util.rs

@@ -41,7 +41,7 @@ impl MemberExt for Member {
     fn as_ident(&self) -> Ident {
         match self {
             Member::Named(ident) => ident.clone(),
-            Member::Unnamed(Index { index, .. }) => format_ident!("_{index}"),
+            Member::Unnamed(Index { index, span }) => format_ident!("_{index}", span = *span),
         }
     }
 

tests/macro-hygiene.rs

@@ -1,3 +1,5 @@
+use pin_init::*;
+
 macro_rules! wrap_init {
     ($($args:tt)*) => {
         ::pin_init::init!(
@@ -12,11 +14,18 @@ struct Foo {
     c: u32,
 }
 
+#[pin_data]
+struct SlotName {
+    slot: u32,
+}
+
 fn main() {
     let c = 3;
     let _ = wrap_init!(Foo {
         a: 1,
         b <- 2,
         c,
     });
+
+    let _ = pin_init!(SlotName { slot: 1 });
 }

tests/ui/compile-fail/init/colon_instead_of_arrow.stderr

@@ -5,20 +5,18 @@ error[E0308]: mismatched types
    |                 ------------------ the found opaque type
 ...
 21 |         pin_init!(Self { bar: Bar::new() })
-   |         ----------------------^^^^^^^^^^---
-   |         |                     |
-   |         |                     expected `Bar`, found opaque type
-   |         arguments to this method are incorrect
+   |                          -----^^^^^^^^^^
+   |                          |    |
+   |                          |    expected `Bar`, found opaque type
+   |                          arguments to this method are incorrect
    |
    = note:   expected struct `Bar`
            found opaque type `impl pin_init::PinInit<Bar>`
 help: the return type of this call is `impl pin_init::PinInit<Bar>` due to the type of the argument passed
-  --> tests/ui/compile-fail/init/colon_instead_of_arrow.rs:21:9
+  --> tests/ui/compile-fail/init/colon_instead_of_arrow.rs:21:26
    |
 21 |         pin_init!(Self { bar: Bar::new() })
-   |         ^^^^^^^^^^^^^^^^^^^^^^----------^^^
-   |                               |
-   |                               this argument influences the return type of `write`
+   |                          ^^^  ---------- this argument influences the return type of `write`
 note: method defined here
   --> src/__internal.rs
    |

tests/ui/compile-fail/init/data_access.stderr

@@ -1,17 +1,5 @@
 error[E0425]: cannot find value `__data` in this scope
-  --> tests/ui/compile-fail/init/data_access.rs:9:21
-   |
- 9 |             let _ = __data;
-   |                     ^^^^^^ not found in this scope
-   |
-help: an identifier with the same name is defined here, but is not accessible due to macro hygiene
-  --> tests/ui/compile-fail/init/data_access.rs:7:13
-   |
- 7 |       let _ = pin_init!(Foo {
-   |  _____________^
- 8 | |         _: {
- 9 | |             let _ = __data;
-10 | |         },
-11 | |     });
-   | |______^
-   = note: this error originates in the macro `pin_init` (in Nightly builds, run with -Z macro-backtrace for more info)
+ --> tests/ui/compile-fail/init/data_access.rs:9:21
+  |
+9 |             let _ = __data;
+  |                     ^^^^^^ not found in this scope

tests/ui/compile-fail/init/early_return.stderr

@@ -20,17 +20,12 @@ note: tuple variant defined here
    |     ^^
 
 warning: unreachable statement
-  --> tests/ui/compile-fail/init/early_return.rs:8:13
+  --> tests/ui/compile-fail/init/early_return.rs:12:9
    |
- 8 |       let _ = init!(Foo {
-   |  _____________^
- 9 | |         _: {
-10 | |             return Ok(());
-   | |             ------------- any code following this expression is unreachable
-11 | |         },
-12 | |         a: 42,
-13 | |     });
-   | |______^ unreachable statement
+10 |             return Ok(());
+   |             ------------- any code following this expression is unreachable
+11 |         },
+12 |         a: 42,
+   |         ^^^^^ unreachable statement
    |
    = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default
-   = note: this warning originates in the macro `init` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui/compile-fail/init/field_value_wrong_type.stderr

@@ -2,18 +2,16 @@ error[E0308]: mismatched types
  --> tests/ui/compile-fail/init/field_value_wrong_type.rs:8:28
   |
 8 |     let _ = init!(Foo { a: () });
-  |             ---------------^^---
-  |             |              |
-  |             |              expected `usize`, found `()`
-  |             arguments to this method are incorrect
+  |                         ---^^
+  |                         |  |
+  |                         |  expected `usize`, found `()`
+  |                         arguments to this method are incorrect
   |
 help: the return type of this call is `()` due to the type of the argument passed
- --> tests/ui/compile-fail/init/field_value_wrong_type.rs:8:13
+ --> tests/ui/compile-fail/init/field_value_wrong_type.rs:8:25
   |
 8 |     let _ = init!(Foo { a: () });
-  |             ^^^^^^^^^^^^^^^--^^^
-  |                            |
-  |                            this argument influences the return type of `write`
+  |                         ^  -- this argument influences the return type of `write`
 note: method defined here
  --> src/__internal.rs
   |

tests/ui/compile-fail/init/invalid_init.stderr

@@ -1,12 +1,11 @@
 error[E0277]: the trait bound `impl pin_init::PinInit<Bar>: Init<Bar, _>` is not satisfied
   --> tests/ui/compile-fail/init/invalid_init.rs:19:16
    |
-18 |       let _ = init!(Foo {
-   |  _____________-
-19 | |         bar <- Bar::new(),
-   | |                ^^^^^^^^^^ the trait `Init<Bar, _>` is not implemented for `impl pin_init::PinInit<Bar>`
-20 | |     });
-   | |______- required by a bound introduced by this call
+19 |         bar <- Bar::new(),
+   |         -------^^^^^^^^^^
+   |         |      |
+   |         |      the trait `Init<Bar, _>` is not implemented for `impl pin_init::PinInit<Bar>`
+   |         required by a bound introduced by this call
    |
 help: the following other types implement trait `Init<T, E>`
   --> src/lib.rs

tests/ui/compile-fail/init/missing_comma_with_zeroable.stderr

@@ -1,24 +1,19 @@
 error[E0308]: mismatched types
   --> tests/ui/compile-fail/init/missing_comma_with_zeroable.rs:12:12
    |
-11 |       let _ = init!(Foo {
-   |  _____________-
-12 | |         a: 0..Zeroable::init_zeroed()
-   | |            ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `usize`, found `Range<{integer}>`
-13 | |     });
-   | |______- arguments to this method are incorrect
+12 |         a: 0..Zeroable::init_zeroed()
+   |         ---^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |  |
+   |         |  expected `usize`, found `Range<{integer}>`
+   |         arguments to this method are incorrect
    |
    = note: expected type `usize`
             found struct `std::ops::Range<{integer}>`
 help: the return type of this call is `std::ops::Range<{integer}>` due to the type of the argument passed
-  --> tests/ui/compile-fail/init/missing_comma_with_zeroable.rs:11:13
+  --> tests/ui/compile-fail/init/missing_comma_with_zeroable.rs:12:9
    |
-11 |       let _ = init!(Foo {
-   |  _____________^
-12 | |         a: 0..Zeroable::init_zeroed()
-   | |            -------------------------- this argument influences the return type of `write`
-13 | |     });
-   | |______^
+12 |         a: 0..Zeroable::init_zeroed()
+   |         ^  -------------------------- this argument influences the return type of `write`
 note: method defined here
   --> src/__internal.rs
    |

tests/ui/compile-fail/init/no_error_coercion.stderr

@@ -1,14 +1,11 @@
 error[E0277]: `?` couldn't convert the error to `std::alloc::AllocError`
-  --> tests/ui/compile-fail/init/no_error_coercion.rs:19:22
+  --> tests/ui/compile-fail/init/no_error_coercion.rs:18:15
    |
-16 | /         init!(Self {
-17 | |             a: Box::new(42),
-18 | |             bar <- init!(Bar { b: 42 }),
-19 | |         }? AllocError)
-   | |                      ^
-   | |                      |
-   | |______________________the trait `From<!>` is not implemented for `std::alloc::AllocError`
-   |                        this can't be annotated with `?` because it has type `Result<_, !>`
+18 |             bar <- init!(Bar { b: 42 }),
+   |             --^------------------------
+   |             | |
+   |             | the trait `From<!>` is not implemented for `std::alloc::AllocError`
+   |             this can't be annotated with `?` because it has type `Result<_, !>`
    |
    = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
    = note: this error originates in the macro `init` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/ui/compile-fail/init/shadowing_field.stderr

@@ -2,18 +2,16 @@ error[E0308]: mismatched types
   --> tests/ui/compile-fail/init/shadowing_field.rs:10:31
    |
 10 |     let _ = init!(Foo { x, y: x });
-   |             ------------------^---
-   |             |                 |
-   |             |                 expected `usize`, found `&mut usize`
-   |             arguments to this method are incorrect
+   |                            ---^
+   |                            |  |
+   |                            |  expected `usize`, found `&mut usize`
+   |                            arguments to this method are incorrect
    |
 help: the return type of this call is `&mut usize` due to the type of the argument passed
-  --> tests/ui/compile-fail/init/shadowing_field.rs:10:13
+  --> tests/ui/compile-fail/init/shadowing_field.rs:10:28
    |
 10 |     let _ = init!(Foo { x, y: x });
-   |             ^^^^^^^^^^^^^^^^^^-^^^
-   |                               |
-   |                               this argument influences the return type of `write`
+   |                            ^  - this argument influences the return type of `write`
 note: method defined here
   --> src/__internal.rs
    |