Preserve all spans for closure captures, not just one

This is important for the "convert closure to fn" assist, as it needs to find and modify the places the captures are used.

Author: ChayimFriedman2

src/tools/rust-analyzer/crates/hir-ty/src/infer.rs

@@ -59,6 +59,7 @@ use crate::{
     generics::Generics,
     infer::{coerce::CoerceMany, unify::InferenceTable},
     lower::ImplTraitLoweringMode,
+    mir::MirSpan,
     to_assoc_type_id,
     traits::FnTrait,
     utils::{InTypeConstIdMetadata, UnevaluatedConstEvaluatorFolder},
@@ -553,6 +554,12 @@ pub(crate) struct InferenceContext<'a> {
 
     // fields related to closure capture
     current_captures: Vec<CapturedItemWithoutTy>,
+    /// A stack that has an entry for each projection in the current capture.
+    ///
+    /// For example, in `a.b.c`, we capture the spans of `a`, `a.b`, and `a.b.c`.
+    /// We do that because sometimes we truncate projections (when a closure captures
+    /// both `a.b` and `a.b.c`), and we want to provide accurate spans in this case.
+    current_capture_span_stack: Vec<MirSpan>,
     current_closure: Option<ClosureId>,
     /// Stores the list of closure ids that need to be analyzed before this closure. See the
     /// comment on `InferenceContext::sort_closures`
@@ -634,6 +641,7 @@ impl<'a> InferenceContext<'a> {
             breakables: Vec::new(),
             deferred_cast_checks: Vec::new(),
             current_captures: Vec::new(),
+            current_capture_span_stack: Vec::new(),
             current_closure: None,
             deferred_closures: FxHashMap::default(),
             closure_dependencies: FxHashMap::default(),