Keep spans for generics in #[derive(_)] desugaring

compiler/rustc_builtin_macros/src/deriving/generic/ty.rs

@@ -211,14 +211,6 @@ fn mk_ty_param(
     cx.typaram(span, Ident::new(name, span), attrs.to_owned(), bounds, None)
 }
 
-fn mk_generics(params: Vec<ast::GenericParam>, span: Span) -> Generics {
-    Generics {
-        params,
-        where_clause: ast::WhereClause { has_where_token: false, predicates: Vec::new(), span },
-        span,
-    }
-}
-
 /// Bounds on type parameters.
 #[derive(Clone)]
 pub struct Bounds {
@@ -236,7 +228,7 @@ impl Bounds {
         self_ty: Ident,
         self_generics: &Generics,
     ) -> Generics {
-        let generic_params = self
+        let params = self
             .bounds
             .iter()
             .map(|t| {
@@ -245,7 +237,11 @@ impl Bounds {
             })
             .collect();
 
-        mk_generics(generic_params, span)
+        Generics {
+            params,
+            where_clause: ast::WhereClause { has_where_token: false, predicates: Vec::new(), span },
+            span,
+        }
     }
 }
 

compiler/rustc_hir/src/hir.rs

@@ -17,8 +17,7 @@ use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable_Generic;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
-use rustc_span::{def_id::LocalDefId, BytePos};
-use rustc_span::{MultiSpan, Span, DUMMY_SP};
+use rustc_span::{def_id::LocalDefId, BytePos, MultiSpan, Span, DUMMY_SP};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use rustc_target::spec::abi::Abi;
 
@@ -526,12 +525,20 @@ pub struct GenericParam<'hir> {
 }
 
 impl GenericParam<'hir> {
-    pub fn bounds_span(&self) -> Option<Span> {
-        self.bounds.iter().fold(None, |span, bound| {
-            let span = span.map(|s| s.to(bound.span())).unwrap_or_else(|| bound.span());
-
-            Some(span)
-        })
+    pub fn bounds_span_for_suggestions(&self) -> Option<Span> {
+        self.bounds
+            .iter()
+            .fold(None, |span: Option<Span>, bound| {
+                // We include bounds that come from a `#[derive(_)]` but point at the user's code,
+                // as we use this method to get a span appropriate for suggestions.
+                if !bound.span().can_be_used_for_suggestions() {
+                    None
+                } else {
+                    let span = span.map(|s| s.to(bound.span())).unwrap_or_else(|| bound.span());
+                    Some(span)
+                }
+            })
+            .map(|sp| sp.shrink_to_hi())
     }
 }
 

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -270,7 +270,7 @@ pub fn suggest_constraining_type_param(
         // `where` clause instead of `trait Base<T: Copy = String>: Super<T>`.
         && !matches!(param.kind, hir::GenericParamKind::Type { default: Some(_), .. })
     {
-        if let Some(bounds_span) = param.bounds_span() {
+        if let Some(span) = param.bounds_span_for_suggestions() {
             // If user has provided some bounds, suggest restricting them:
             //
             //   fn foo<T: Foo>(t: T) { ... }
@@ -284,7 +284,7 @@ pub fn suggest_constraining_type_param(
             //          --
             //          |
             //          replace with: `T: Bar +`
-            suggest_restrict(bounds_span.shrink_to_hi());
+            suggest_restrict(span);
         } else {
             // If user hasn't provided any bounds, suggest adding a new one:
             //

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1735,7 +1735,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                         (generics.span, format!("<{}>", ident))
                     };
                     // Do not suggest if this is coming from macro expansion.
-                    if !span.from_expansion() {
+                    if span.can_be_used_for_suggestions() {
                         return Some((
                             span.shrink_to_hi(),
                             msg,
@@ -1803,7 +1803,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
         );
         err.span_label(lifetime_ref.span, "undeclared lifetime");
         let mut suggests_in_band = false;
-        let mut suggest_note = true;
+        let mut suggested_spans = vec![];
         for missing in &self.missing_named_lifetime_spots {
             match missing {
                 MissingLifetimeSpot::Generics(generics) => {
@@ -1821,23 +1821,17 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                         suggests_in_band = true;
                         (generics.span, format!("<{}>", lifetime_ref))
                     };
-                    if !span.from_expansion() {
+                    if suggested_spans.contains(&span) {
+                        continue;
+                    }
+                    suggested_spans.push(span);
+                    if span.can_be_used_for_suggestions() {
                         err.span_suggestion(
                             span,
                             &format!("consider introducing lifetime `{}` here", lifetime_ref),
                             sugg,
                             Applicability::MaybeIncorrect,
                         );
-                    } else if suggest_note {
-                        suggest_note = false; // Avoid displaying the same help multiple times.
-                        err.span_label(
-                            span,
-                            &format!(
-                                "lifetime `{}` is missing in item created through this procedural \
-                                 macro",
-                                lifetime_ref,
-                            ),
-                        );
                     }
                 }
                 MissingLifetimeSpot::HigherRanked { span, span_type } => {

compiler/rustc_span/src/lib.rs

@@ -551,6 +551,16 @@ impl Span {
         matches!(self.ctxt().outer_expn_data().kind, ExpnKind::Macro(MacroKind::Derive, _))
     }
 
+    /// Gate suggestions that would not be appropriate in a context the user didn't write.
+    pub fn can_be_used_for_suggestions(self) -> bool {
+        !self.from_expansion()
+        // FIXME: If this span comes from a `derive` macro but it points at code the user wrote,
+        // the callsite span and the span will be pointing at different places. It also means that
+        // we can safely provide suggestions on this span.
+            || (matches!(self.ctxt().outer_expn_data().kind, ExpnKind::Macro(MacroKind::Derive, _))
+                && self.parent_callsite().map(|p| (p.lo(), p.hi())) != Some((self.lo(), self.hi())))
+    }
+
     #[inline]
     pub fn with_root_ctxt(lo: BytePos, hi: BytePos) -> Span {
         Span::new(lo, hi, SyntaxContext::root(), None)

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -262,16 +262,16 @@ fn suggest_restriction(
             match generics
                 .params
                 .iter()
-                .map(|p| p.bounds_span().unwrap_or(p.span))
-                .filter(|&span| generics.span.contains(span) && span.desugaring_kind().is_none())
+                .map(|p| p.bounds_span_for_suggestions().unwrap_or(p.span.shrink_to_hi()))
+                .filter(|&span| generics.span.contains(span) && span.can_be_used_for_suggestions())
                 .max_by_key(|span| span.hi())
             {
                 // `fn foo(t: impl Trait)`
                 //        ^ suggest `<T: Trait>` here
                 None => (generics.span, format!("<{}>", type_param)),
                 // `fn foo<A>(t: impl Trait)`
                 //        ^^^ suggest `<A, T: Trait>` here
-                Some(span) => (span.shrink_to_hi(), format!(", {}", type_param)),
+                Some(span) => (span, format!(", {}", type_param)),
             },
             // `fn foo(t: impl Trait)`
             //                       ^ suggest `where <T as Trait>::A: Bound`

compiler/rustc_typeck/src/collect.rs

@@ -177,11 +177,9 @@ crate fn placeholder_type_error(
         sugg.push((arg.span, (*type_name).to_string()));
     } else {
         let last = generics.iter().last().unwrap();
-        sugg.push((
-            // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
-            last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
-            format!(", {}", type_name),
-        ));
+        // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
+        let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
+        sugg.push((span, format!(", {}", type_name)));
     }
 
     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);

src/test/ui/issues/issue-38821.stderr

@@ -10,6 +10,10 @@ note: required because of the requirements on the impl of `IntoNullable` for `<C
 LL | impl<T: NotNull> IntoNullable for T {
    |                  ^^^^^^^^^^^^     ^
    = note: this error originates in the derive macro `Copy` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider further restricting the associated type
+   |
+LL |     Expr: Expression<SqlType=<Col::SqlType as IntoNullable>::Nullable>, <Col as Expression>::SqlType: NotNull,
+   |                                                                       +++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-50480.rs

@@ -1,8 +1,17 @@
 #[derive(Clone, Copy)]
 //~^ ERROR the trait `Copy` may not be implemented for this type
-struct Foo(NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
 //~^ ERROR cannot find type `NotDefined` in this scope
 //~| ERROR cannot find type `NotDefined` in this scope
+//~| ERROR cannot find type `N` in this scope
+//~| ERROR cannot find type `N` in this scope
+//~| ERROR `i32` is not an iterator
+
+#[derive(Clone, Copy)]
+//~^ ERROR the trait `Copy` may not be implemented for this type
+struct Bar<T>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+//~^ ERROR cannot find type `NotDefined` in this scope
+//~| ERROR cannot find type `N` in this scope
 //~| ERROR `i32` is not an iterator
 
 fn main() {}

src/test/ui/issues/issue-50480.stderr

@@ -1,20 +1,61 @@
-error[E0412]: cannot find type `NotDefined` in this scope
+error[E0412]: cannot find type `N` in this scope
   --> $DIR/issue-50480.rs:3:12
    |
-LL | struct Foo(NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
-   |            ^^^^^^^^^^ not found in this scope
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |           -^ not found in this scope
+   |           |
+   |           help: you might be missing a type parameter: `<N>`
 
 error[E0412]: cannot find type `NotDefined` in this scope
+  --> $DIR/issue-50480.rs:3:15
+   |
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |               ^^^^^^^^^^ not found in this scope
+
+error[E0412]: cannot find type `N` in this scope
   --> $DIR/issue-50480.rs:3:12
    |
-LL | struct Foo(NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
-   |            ^^^^^^^^^^ not found in this scope
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |           -^ not found in this scope
+   |           |
+   |           help: you might be missing a type parameter: `<N>`
+
+error[E0412]: cannot find type `NotDefined` in this scope
+  --> $DIR/issue-50480.rs:3:15
+   |
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |           -   ^^^^^^^^^^ not found in this scope
+   |           |
+   |           help: you might be missing a type parameter: `<NotDefined>`
+
+error[E0412]: cannot find type `N` in this scope
+  --> $DIR/issue-50480.rs:12:18
+   |
+LL | struct Bar<T>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |            -     ^
+   |            |
+   |            similarly named type parameter `T` defined here
+   |
+help: a type parameter with a similar name exists
+   |
+LL | struct Bar<T>(T, T, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                  ~
+help: you might be missing a type parameter
+   |
+LL | struct Bar<T, N>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |             +++
+
+error[E0412]: cannot find type `NotDefined` in this scope
+  --> $DIR/issue-50480.rs:12:21
+   |
+LL | struct Bar<T>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                     ^^^^^^^^^^ not found in this scope
 
 error[E0277]: `i32` is not an iterator
-  --> $DIR/issue-50480.rs:3:24
+  --> $DIR/issue-50480.rs:3:27
    |
-LL | struct Foo(NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^ `i32` is not an iterator
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^ `i32` is not an iterator
    |
    = help: the trait `Iterator` is not implemented for `i32`
    = note: if you want to iterate between `start` until a value `end`, use the exclusive range syntax `start..end` or the inclusive range syntax `start..=end`
@@ -25,14 +66,36 @@ error[E0204]: the trait `Copy` may not be implemented for this type
 LL | #[derive(Clone, Copy)]
    |                 ^^^^
 LL |
-LL | struct Foo(NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
-   |                                                 --------  ------ this field does not implement `Copy`
-   |                                                 |
-   |                                                 this field does not implement `Copy`
+LL | struct Foo(N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                                                    --------  ------ this field does not implement `Copy`
+   |                                                    |
+   |                                                    this field does not implement `Copy`
+   |
+   = note: this error originates in the derive macro `Copy` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: `i32` is not an iterator
+  --> $DIR/issue-50480.rs:12:33
+   |
+LL | struct Bar<T>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^^ `i32` is not an iterator
+   |
+   = help: the trait `Iterator` is not implemented for `i32`
+   = note: if you want to iterate between `start` until a value `end`, use the exclusive range syntax `start..end` or the inclusive range syntax `start..=end`
+
+error[E0204]: the trait `Copy` may not be implemented for this type
+  --> $DIR/issue-50480.rs:10:17
+   |
+LL | #[derive(Clone, Copy)]
+   |                 ^^^^
+LL |
+LL | struct Bar<T>(T, N, NotDefined, <i32 as Iterator>::Item, Vec<i32>, String);
+   |                                                          --------  ------ this field does not implement `Copy`
+   |                                                          |
+   |                                                          this field does not implement `Copy`
    |
    = note: this error originates in the derive macro `Copy` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 4 previous errors
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0204, E0277, E0412.
 For more information about an error, try `rustc --explain E0204`.

src/test/ui/lifetimes/undeclared-lifetime-used-in-debug-macro-issue-70152.stderr

@@ -11,9 +11,8 @@ LL |     a: &'b str,
 error[E0261]: use of undeclared lifetime name `'b`
   --> $DIR/undeclared-lifetime-used-in-debug-macro-issue-70152.rs:3:9
    |
-LL | #[derive(Eq, PartialEq)]
-   |          -- lifetime `'b` is missing in item created through this procedural macro
 LL | struct Test {
+   |            - help: consider introducing lifetime `'b` here: `<'b>`
 LL |     a: &'b str,
    |         ^^ undeclared lifetime
    |