Names from lib end up in scope of `with builtins`, cause incorrect "unused" warning

[iFreilicht]

Describe the bug
Consider this simple nix file:

with (import <nixpkgs> { }).lib; with builtins; generators.toPretty { } "asdf"

It evaluates fine:

# nix eval -f repro-with-builtins.nix
"\"asdf\""

But nixd displays an "unused with expression" warning:

When removing the expression, the warning goes away:

with builtins; generators.toPretty { } "asdf"

However, builtins doesn't contain generators at all, that's from lib!

#  nix eval -f repro-with-builtins.nix
error:
       … while evaluating the file '/Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix':

       error: undefined variable 'generators'
       at /Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix:1:16:
            1| with builtins; generators.toPretty { } "asdf"
             |                ^
            2|

So it seems this is a bug that somehow causes with builtins; to be treated as if it imports the exact same names as with lib; would.

Logs (Required)

V[11:07:37.154] 93541: <<< {"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix","version":61},"contentChanges":[{"range":{"start":{"line":0,"character":0},"end":{"line":0,"character":0}},"rangeLength":0,"text":"with (import <nixpkgs> { }).lib;"}]}}
I[11:07:37.154] 93541: <-- textDocument/didChange
I[11:07:37.154] 93541: --> notify textDocument/publishDiagnostics
V[11:07:37.154] 93541: >>> {"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"diagnostics":[{"code":"sema-extra-with","message":"unused `with` expression (fix available)","range":{"end":{"character":4,"line":0},"start":{"character":0,"line":0}},"relatedInformation":[],"severity":2,"source":"nixf"}],"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix","version":61}}
V[11:07:37.182] 93541: <<< {"jsonrpc":"2.0","id":46,"method":"textDocument/inlayHint","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"},"range":{"start":{"line":0,"character":0},"end":{"line":4,"character":0}}}}
I[11:07:37.182] 93541: <-- textDocument/inlayHint(46)
I[11:07:37.182] 93541: --> reply:textDocument/inlayHint(46)
V[11:07:37.182] 93541: >>> {"id":46,"jsonrpc":"2.0","result":[]}
V[11:07:37.414] 93541: <<< {"jsonrpc":"2.0","id":47,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"},"range":{"start":{"line":0,"character":0},"end":{"line":0,"character":0}},"context":{"diagnostics":[{"range":{"start":{"line":0,"character":0},"end":{"line":0,"character":4}},"message":"unused `with` expression (fix available)","code":"sema-extra-with","severity":2,"relatedInformation":[],"source":"nixf"}],"triggerKind":2}}}
I[11:07:37.414] 93541: <-- textDocument/codeAction(47)
I[11:07:37.414] 93541: --> reply:textDocument/codeAction(47)
V[11:07:37.414] 93541: >>> {"id":47,"jsonrpc":"2.0","result":[{"edit":{"changes":{"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix":[{"newText":"","range":{"end":{"character":4,"line":0},"start":{"character":0,"line":0}}},{"newText":"","range":{"end":{"character":32,"line":0},"start":{"character":31,"line":0}}},{"newText":"","range":{"end":{"character":31,"line":0},"start":{"character":5,"line":0}}}]}},"kind":"quickfix","title":"remove `with` expression"}]}
V[11:07:37.454] 93541: <<< {"jsonrpc":"2.0","id":48,"method":"textDocument/semanticTokens/full","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"}}}
I[11:07:37.454] 93541: <-- textDocument/semanticTokens/full(48)
I[11:07:37.454] 93541: --> reply:textDocument/semanticTokens/full(48)
V[11:07:37.454] 93541: >>> {"id":48,"jsonrpc":"2.0","result":{"data":[0,6,6,4,1,0,22,3,3,0,0,10,8,4,1,0,10,10,6,4,0,11,8,3,0,0,13,6,1,0],"resultId":""}}
V[11:07:37.505] 93541: <<< {"jsonrpc":"2.0","id":49,"method":"textDocument/documentSymbol","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"}}}
I[11:07:37.505] 93541: <-- textDocument/documentSymbol(49)
I[11:07:37.505] 93541: --> reply:textDocument/documentSymbol(49)
V[11:07:37.505] 93541: >>> {"id":49,"jsonrpc":"2.0","result":[{"detail":"identifier","kind":24,"name":"import","range":{"end":{"character":12,"line":0},"start":{"character":6,"line":0}},"selectionRange":{"end":{"character":12,"line":0},"start":{"character":6,"line":0}}},{"detail":"attribute name","kind":7,"name":"lib","range":{"end":{"character":31,"line":0},"start":{"character":28,"line":0}},"selectionRange":{"end":{"character":31,"line":0},"start":{"character":28,"line":0}}},{"detail":"identifier","kind":24,"name":"builtins","range":{"end":{"character":46,"line":0},"start":{"character":38,"line":0}},"selectionRange":{"end":{"character":46,"line":0},"start":{"character":38,"line":0}}},{"detail":"identifier","kind":13,"name":"generators","range":{"end":{"character":58,"line":0},"start":{"character":48,"line":0}},"selectionRange":{"end":{"character":58,"line":0},"start":{"character":48,"line":0}}},{"detail":"attribute name","kind":7,"name":"toPretty","range":{"end":{"character":67,"line":0},"start":{"character":59,"line":0}},"selectionRange":{"end":{"character":67,"line":0},"start":{"character":59,"line":0}}},{"detail":"string","kind":15,"name":"asdf","range":{"end":{"character":78,"line":0},"start":{"character":72,"line":0}},"selectionRange":{"end":{"character":78,"line":0},"start":{"character":72,"line":0}}}]}
V[11:07:37.511] 93541: <<< {"jsonrpc":"2.0","id":50,"method":"textDocument/documentSymbol","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"}}}
I[11:07:37.511] 93541: <-- textDocument/documentSymbol(50)
I[11:07:37.511] 93541: --> reply:textDocument/documentSymbol(50)
V[11:07:37.511] 93541: >>> {"id":50,"jsonrpc":"2.0","result":[{"detail":"identifier","kind":24,"name":"import","range":{"end":{"character":12,"line":0},"start":{"character":6,"line":0}},"selectionRange":{"end":{"character":12,"line":0},"start":{"character":6,"line":0}}},{"detail":"attribute name","kind":7,"name":"lib","range":{"end":{"character":31,"line":0},"start":{"character":28,"line":0}},"selectionRange":{"end":{"character":31,"line":0},"start":{"character":28,"line":0}}},{"detail":"identifier","kind":24,"name":"builtins","range":{"end":{"character":46,"line":0},"start":{"character":38,"line":0}},"selectionRange":{"end":{"character":46,"line":0},"start":{"character":38,"line":0}}},{"detail":"identifier","kind":13,"name":"generators","range":{"end":{"character":58,"line":0},"start":{"character":48,"line":0}},"selectionRange":{"end":{"character":58,"line":0},"start":{"character":48,"line":0}}},{"detail":"attribute name","kind":7,"name":"toPretty","range":{"end":{"character":67,"line":0},"start":{"character":59,"line":0}},"selectionRange":{"end":{"character":67,"line":0},"start":{"character":59,"line":0}}},{"detail":"string","kind":15,"name":"asdf","range":{"end":{"character":78,"line":0},"start":{"character":72,"line":0}},"selectionRange":{"end":{"character":78,"line":0},"start":{"character":72,"line":0}}}]}
V[11:07:37.956] 93541: <<< {"jsonrpc":"2.0","id":51,"method":"textDocument/inlayHint","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"},"range":{"start":{"line":0,"character":0},"end":{"line":4,"character":0}}}}
I[11:07:37.956] 93541: <-- textDocument/inlayHint(51)
I[11:07:37.959] 93541: --> reply:textDocument/inlayHint(51)
V[11:07:37.959] 93541: >>> {"id":51,"jsonrpc":"2.0","result":[]}
V[11:07:38.156] 93541: <<< {"jsonrpc":"2.0","id":52,"method":"textDocument/documentLink","params":{"textDocument":{"uri":"file:///Users/feuh/repos/experiments/nixd-repro/repro-with-builtins.nix"}}}
I[11:07:38.158] 93541: <-- textDocument/documentLink(52)
I[11:07:38.158] 93541: --> reply:textDocument/documentLink(52)
V[11:07:38.158] 93541: >>> {"id":52,"jsonrpc":"2.0","result":[]}

Configuration

If you have some custom configuration, please paste it here.

To Reproduce

1. Create a file with the content with (import <nixpkgs> { }).lib; with builtins; generators.toPretty { } "asdf"
2. Run nixd
3. Observe the incorrect warning

Expected behavior
I would expect nixd to correctly determine that some names from with lib; are used that are not available in with builtins;

Screenshots
See above.

Additional context
None.

[inclyc]

It is currently assumed that all non-statically defined things originate from the nearest "with" declaration because libnixf does not perform any evaluation.

I would expect nixd to correctly determine that some names from with lib; are used that are not available in with builtins;

This likely means our variable name lookup code will need a special case for the builtins variable, which I think is problematic.

I've considered an alternative approach: ensuring that all non-statically defined variables (which should come from "with" expressions) keep all nested "with" declarations active. Do you think this would be acceptable?

[iFreilicht]

Yeah that sounds right. Just for my understanding, would this mean that in the case above, a warning about with builtins; being redundant would be shown? Because with doesn't shadow existing names, this is the case, but I'm uncertain how you determine that a with expression is still "active".

[inclyc]

being redundant would be shown

No, both of them will be considered as alive.

Because with doesn't shadow existing names,

This is not right. nested with also shadows other with.

[iFreilicht]

No, both of them will be considered as alive.

Okay. That's not perfect, but better than showing an incorrect warning, so it fixes the issue at hand.

This is not right. nested with also shadows other with.

Oh true, I confused it with let in conjunction with with:

nix-repl> with {a=1;}; with {a=2;}; a 
2

nix-repl> let a=1; in let a=2; in a  
2

nix-repl> with {a=1;}; let a=2; in a    
2

nix-repl> let a=1; in with {a=2;}; a    
1