Fix backtrace line numbers following macros

The `CodeInfo` block has a field `codelocs` that indexes into an array
with full `LineInfoNode` objects. This data model allows de-duplication,
and in practice it does (only) `uniq`-style deduplication, i.e. only
consecutive equal objects are deduplicated by this scheme.

The lambda `compact-ir` generates this structure. This commit fixes a bug
where it mixes monotonously increasing the indices (for `codeloc`) with
push/pop operations. This is wrong because the latest `LineInfoNode`
object is always at the end of the current size of the array; not
one position after the current `LineInfoNode`.

src/julia-syntax.scm

@@ -4049,13 +4049,13 @@ f(x) = yt(x)
                                                    `(line ,current-line ,current-file)
                                                    `(line ,current-line ,current-file ,(caar locstack)))
                                                linetable))
-                         (set! current-loc (+ 1 current-loc)))))
+                         (set! current-loc (- (length linetable) 1)))))
                   ((and (length> e 2) (eq? (car e) 'meta) (eq? (cadr e) 'push_loc))
                    (set! locstack (cons (list current-loc current-line current-file) locstack))
                    (set! current-file (caddr e))
                    (set! current-line 0)
                    (set! linetable (cons `(line ,current-line ,current-file ,current-loc) linetable))
-                   (set! current-loc (+ 1 current-loc)))
+                   (set! current-loc (- (length linetable) 1)))
                   ((and (length= e 2) (eq? (car e) 'meta) (eq? (cadr e) 'pop_loc))
                    (let ((l (car locstack)))
                      (set! locstack (cdr locstack))

test/backtrace.jl

@@ -177,3 +177,15 @@ let bt, found = false
     end
     @test found
 end
+
+# issue 28618
+let bt, found = false
+    @info ""
+    bt = backtrace()
+    for frame in map(StackTraces.lookup, bt)
+        if frame[1].line == @__LINE__() - 2 && frame[1].file == Symbol(@__FILE__)
+            found = true; break
+        end
+    end
+    @test found
+end