I've long dreamt of a system that compiles to native code, but stores a compressed SSA form (similar to SafeTSA or LLVM bitcode) in the binary for efficient runtime re-optimization based on profiling, somewhat similar to current Android Runtimes. One could then have several levels of debugging symbols, one that gives names to local variables represented by CFG nodes, and another that adds a compressed diff between some standardized decompiler output and the original source.
You could then decompile to some alternative syntax, but you'd lose any idiosyncratic formatting represented by the compressed diff.
I'm not aware how to get byte-for-byte identical source out of a Java class file or .NET assembly.
Last I checked, Java AoT compilation precluded runtime re-optimization, though I presume they've fixed that by now.
Last I checked, they both used stack-based bytecode, which typically takes longer to JIT and results in slower native code than a compressed SSA / control flow graph (see the SafeTSA papers).
Though SSA is deferred to JIT/ILC instead. In either case you get the access to all the actual low-level bits when you need to. No other portable target lets you do that.
If you add an extra blank line, or add a trailing space to a line, can you really get that back out from a .NET assembly? Normal disassembly at a minimum results in a loss of formatting.
You could then decompile to some alternative syntax, but you'd lose any idiosyncratic formatting represented by the compressed diff.