Auto merge of #112945 - compiler-errors:tighten-span-of-adjustment-error, r=oli-obk

(re-)tighten sourceinfo span of adjustments in MIR

Diagnostics rely on the spans of MIR statements being (approximately) correct in order to give suggestions relative to that span (i.e. `shrink_to_hi` and `shrink_to_lo`).

I discovered that we're *intentionally* lowering THIR exprs with their parent expr's span if they come from adjustments that are due to a parent expression. While I understand why that may be desirable to demonstrate the relationship of an adjustment and the expression that requires it, it leads to

1. very verbose borrowck output
2. incorrect spans for suggestions

Some diagnostics get around that by giving suggestions relative to other spans we've collected during MIR lowering, such as the span of the method's identifier (e.g. `name` in `.name()`), but this doesn't work too well when things come from desugaring.

I assume it also has lead to numerous tweaks and complications to diagnostics code down the road, which this PR doesn't necessarily aim to fix but may open the gates to fixing later... The last three commits are simplifications due to the fact that we can assume that the move span actually points to what is being moved (and a test).

This regressed in #89110, which was debated somewhat in #90286. cc `@Aaron1011` who originally made this change.

r? diagnostics

Fixes #113547
Fixes #111016

Author: bors

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -1121,7 +1121,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             err.eager_subdiagnostic(
                                 &self.infcx.tcx.sess.parse_sess.span_diagnostic,
                                 CaptureReasonSuggest::FreshReborrow {
-                                    span: fn_call_span.shrink_to_lo(),
+                                    span: move_span.shrink_to_hi(),
                                 });
                         }
                         if let Some(clone_trait) = tcx.lang_items().clone_trait()
@@ -1135,10 +1135,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             && self.infcx.predicate_must_hold_modulo_regions(&o)
                         {
                             err.span_suggestion_verbose(
-                                fn_call_span.shrink_to_lo(),
+                                move_span.shrink_to_hi(),
                                 "you can `clone` the value and consume it, but this might not be \
                                  your desired behavior",
-                                "clone().".to_string(),
+                                ".clone()".to_string(),
                                 Applicability::MaybeIncorrect,
                             );
                         }

compiler/rustc_borrowck/src/session_diagnostics.rs

@@ -398,7 +398,7 @@ pub(crate) enum CaptureReasonSuggest<'tcx> {
     #[suggestion(
         borrowck_suggest_create_freash_reborrow,
         applicability = "maybe-incorrect",
-        code = "as_mut().",
+        code = ".as_mut()",
         style = "verbose"
     )]
     FreshReborrow {