lean4-htt/tests/lean/trailingComma.lean
Joachim Breitner 117f73fc84
feat: linter.unusedSimpArgs (#8901)
This PR adds a linter (`linter.unusedSimpArgs`) that complains when a
simp argument (`simp [foo]`) is unused. It should do the right thing if
the `simp` invocation is run multiple times, e.g. inside `all_goals`. It
does not trigger when the `simp` call is inside a macro. The linter
message contains a clickable hint to remove the simp argument.

I chose to display a separate warning for each unused argument. This
means that the user has to click multiple times to remove all of them
(and wait for re-elaboration in between). But this just means multiple
endorphine kicks, and the main benefit over a single warning that would
have to span the whole argument list is that already the squigglies tell
the users about unused arguments.

This closes #4483.

Making Init and Std clean wrt to this linter revealed close to 1000
unused simp args, a pleasant experience for anyone enjoying tidying
things: #8905
2025-06-22 09:10:21 +00:00

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set_option linter.unusedSimpArgs false
#eval [1,2,3,]
#eval (2,3,)
#eval [1,2,3,,] -- Errors, double trailing comma
#eval (4,5,,,) -- ditto
axiom zeroAdd (x : Nat) : 0 + x = x
theorem rewrite_comma (x y z: Nat) (h₁ : 0 + x = y) (h₂ : 0 + y = z) : x = z := by
rewrite [zeroAdd,] at *;
subst x;
subst y;
exact rfl
theorem simp_comma (x: Nat) : x = x := by
simp [zeroAdd,]