refactor: weaken type of contradiction-irr (#2785)

Author: jamesmckinna

CHANGELOG.md

@@ -17,6 +17,10 @@ Non-backwards compatible changes
 Minor improvements
 ------------------
 
+* The type of `Relation.Nullary.Negation.Core.contradiction-irr` has been further
+  weakened so that the negated hypothesis `¬ A` is marked as irrelevant. This is
+  safe to do, in view of `Relation.Nullary.Recomputable.Properties.¬-recompute`.
+
 * Refactored usages of `+-∸-assoc 1` to `∸-suc` in:
   ```agda
   README.Data.Fin.Relation.Unary.Top

src/Relation/Nullary/Negation/Core.agda

@@ -47,11 +47,11 @@ _¬-⊎_ = [_,_]
 ------------------------------------------------------------------------
 -- Uses of negation
 
-contradiction-irr : .A → ¬ A → Whatever
+contradiction-irr : .A → .(¬ A) → Whatever
 contradiction-irr a ¬a = ⊥-elim-irr (¬a a)
 
 contradiction : A → ¬ A → Whatever
-contradiction a = contradiction-irr a
+contradiction a ¬a = contradiction-irr a ¬a
 
 contradiction₂ : A ⊎ B → ¬ A → ¬ B → Whatever
 contradiction₂ (inj₁ a) ¬a ¬b = contradiction a ¬a