Rollup merge of #112612 - sginnett:issue-105150, r=compiler-errors

Fix explicit-outlives-requirements lint span

Fixes #105150 which caused the span reported by the explicit-outlives-requirements lint to be incorrect when
1) the lint should suggest the entire where clause to be removed and
2) there are inline bounds present that are not inferable outlives requirements

In particular, this would cause rustfix to leave a dangling empty where clause.

Author: matthiaskrgr

compiler/rustc_lint/src/builtin.rs

@@ -2124,12 +2124,16 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
             }
 
             let ty_generics = cx.tcx.generics_of(def_id);
+            let num_where_predicates = hir_generics
+                .predicates
+                .iter()
+                .filter(|predicate| predicate.in_where_clause())
+                .count();
 
             let mut bound_count = 0;
             let mut lint_spans = Vec::new();
             let mut where_lint_spans = Vec::new();
-            let mut dropped_predicate_count = 0;
-            let num_predicates = hir_generics.predicates.len();
+            let mut dropped_where_predicate_count = 0;
             for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
                 let (relevant_lifetimes, bounds, predicate_span, in_where_clause) =
                     match where_predicate {
@@ -2186,8 +2190,8 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                 bound_count += bound_spans.len();
 
                 let drop_predicate = bound_spans.len() == bounds.len();
-                if drop_predicate {
-                    dropped_predicate_count += 1;
+                if drop_predicate && in_where_clause {
+                    dropped_where_predicate_count += 1;
                 }
 
                 if drop_predicate {
@@ -2196,7 +2200,7 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                     } else if predicate_span.from_expansion() {
                         // Don't try to extend the span if it comes from a macro expansion.
                         where_lint_spans.push(predicate_span);
-                    } else if i + 1 < num_predicates {
+                    } else if i + 1 < num_where_predicates {
                         // If all the bounds on a predicate were inferable and there are
                         // further predicates, we want to eat the trailing comma.
                         let next_predicate_span = hir_generics.predicates[i + 1].span();
@@ -2224,9 +2228,10 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                 }
             }
 
-            // If all predicates are inferable, drop the entire clause
+            // If all predicates in where clause are inferable, drop the entire clause
             // (including the `where`)
-            if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
+            if hir_generics.has_where_clause_predicates
+                && dropped_where_predicate_count == num_where_predicates
             {
                 let where_span = hir_generics.where_clause_span;
                 // Extend the where clause back to the closing `>` of the

tests/ui/rust-2018/edition-lint-infer-outlives.fixed

@@ -801,4 +801,10 @@ where
     yoo: &'a U
 }
 
+// https://github.com/rust-lang/rust/issues/105150
+struct InferredWhereBoundWithInlineBound<'a, T: ?Sized>
+{
+    data: &'a T,
+}
+
 fn main() {}

tests/ui/rust-2018/edition-lint-infer-outlives.rs

@@ -801,4 +801,12 @@ where
     yoo: &'a U
 }
 
+// https://github.com/rust-lang/rust/issues/105150
+struct InferredWhereBoundWithInlineBound<'a, T: ?Sized>
+//~^ ERROR outlives requirements can be inferred
+    where T: 'a,
+{
+    data: &'a T,
+}
+
 fn main() {}

tests/ui/rust-2018/edition-lint-infer-outlives.stderr

@@ -10,6 +10,15 @@ note: the lint level is defined here
 LL | #![deny(explicit_outlives_requirements)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: outlives requirements can be inferred
+  --> $DIR/edition-lint-infer-outlives.rs:805:56
+   |
+LL |   struct InferredWhereBoundWithInlineBound<'a, T: ?Sized>
+   |  ________________________________________________________^
+LL | |
+LL | |     where T: 'a,
+   | |________________^ help: remove this bound
+
 error: outlives requirements can be inferred
   --> $DIR/edition-lint-infer-outlives.rs:26:31
    |
@@ -922,5 +931,5 @@ error: outlives requirements can be inferred
 LL |     union BeeWhereOutlivesAyTeeWhereDebug<'a, 'b, T> where 'b: 'a, T: Debug {
    |                                                            ^^^^^^^^ help: remove this bound
 
-error: aborting due to 153 previous errors
+error: aborting due to 154 previous errors