Rollup merge of rust-lang#118967 - RossSmyth:panic-messages, r=TaKO8Ki

Add better ICE messages for some undescriptive panics

Add some better messages at some panics

re: rust-lang#118955

I took a look at some others but either was not able to figure out what they did, or it was unclear what they should say instead. For example in the query system whether each time a poisoned value is matched upon if they should all just call `FatalError.raise()`

Author: matthiaskrgr

compiler/rustc_ast_lowering/src/path.rs

@@ -9,6 +9,7 @@ use rustc_ast::{self as ast, *};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, PartialRes, Res};
 use rustc_hir::GenericArg;
+use rustc_middle::span_bug;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span, DUMMY_SP};
 
@@ -285,7 +286,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let (start, end) = match self.resolver.get_lifetime_res(segment_id) {
             Some(LifetimeRes::ElidedAnchor { start, end }) => (start, end),
             None => return,
-            Some(_) => panic!(),
+            Some(res) => {
+                span_bug!(path_span, "expected an elided lifetime to insert. found {res:?}")
+            }
         };
         let expected_lifetimes = end.as_usize() - start.as_usize();
         debug!(expected_lifetimes);

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1597,7 +1597,9 @@ impl<'a> State<'a> {
             }
             match bound {
                 ast::GenericBound::Outlives(lt) => self.print_lifetime(*lt),
-                _ => panic!(),
+                _ => {
+                    panic!("expected a lifetime bound, found a trait bound")
+                }
             }
         }
     }

compiler/rustc_span/src/caching_source_map_view.rs

@@ -117,7 +117,7 @@ impl<'sm> CachingSourceMapView<'sm> {
         self.time_stamp += 1;
 
         // Check if lo and hi are in the cached lines.
-        let lo_cache_idx = self.cache_entry_index(span_data.lo);
+        let lo_cache_idx: isize = self.cache_entry_index(span_data.lo);
         let hi_cache_idx = self.cache_entry_index(span_data.hi);
 
         if lo_cache_idx != -1 && hi_cache_idx != -1 {
@@ -205,7 +205,9 @@ impl<'sm> CachingSourceMapView<'sm> {
                 (lo_cache_idx as usize, oldest)
             }
             _ => {
-                panic!();
+                panic!(
+                    "the case of neither value being equal to -1 was handled above and the function returns."
+                );
             }
         };