CoreLogging: prevent some Annotated*-related instability

Add some concrete `typeassert`s to increase the resistance of the
sysimage to invalidation by helping inference within the method body.

Author: nsajko

base/logging/ConsoleLogger.jl

@@ -123,9 +123,10 @@ function handle_message(logger::ConsoleLogger, level::LogLevel, message, _module
     # Generate a text representation of the message and all key value pairs,
     # split into lines.  This is specialised to improve type inference,
     # and reduce the risk of resulting method invalidations.
+    annotations_type = Vector{@NamedTuple{region::UnitRange{Int}, label::Symbol, value}}
     message = string(message)
-    msglines = if Base._isannotated(message) && !isempty(Base.annotations(message))
-        message = Base.AnnotatedString(String(message), Base.annotations(message))
+    msglines = if Base._isannotated(message) && !isempty(Base.annotations(message)::annotations_type)
+        message = Base.AnnotatedString(String(message)::String, Base.annotations(message)::annotations_type)
         @NamedTuple{indent::Int, msg::Union{SubString{Base.AnnotatedString{String}}, SubString{String}}}[
             (indent=0, msg=l) for l in split(chomp(message), '\n')]
     else