From 3f9b6fcece3a40d667a50df8e33f1be80a107580 Mon Sep 17 00:00:00 2001
From: Alexander Voigt <ahgvoigt@gmail.com>
Date: Mon, 5 Jan 2026 17:11:51 +0100
Subject: [PATCH] Fix error when BigInt is used as input type

---
 src/Li.jl  | 15 ++++++++++++---
 test/Li.jl |  2 ++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/Li.jl b/src/Li.jl
index 7e9be37..3a31ff6 100644
--- a/src/Li.jl
+++ b/src/Li.jl
@@ -250,7 +250,7 @@ function li_series_unity_pos(n::Integer, z::ComplexOrReal{T}) where T
 
     l2 = l*l
 
-    for j in (n + 3):2:typemax(promote_type(typeof(n), Int64))
+    for j in (n + 3):2:max_n(typeof(n))
         p *= l2/((j - 1)*j)
         old_sum = sum
         sum += zeta(n - j, T)*p
@@ -279,7 +279,7 @@ function li_series_unity_neg(n::Integer, z::Complex{T})::Complex{T} where T
         sum += zeta(n, T)
     end
 
-    for k in kmin:2:typemax(promote_type(typeof(n), Int64))
+    for k in kmin:2:max_n(typeof(n))
         term = zeta(n - k, T)*inv_fac(k, T)*lk
         !isfinite(term) && break
         sum_old = sum
@@ -299,7 +299,7 @@ function li_series_taylor(n::Integer, z::ComplexOrReal)
     sum = z
     zn = z*z
 
-    for k in 2:typemax(promote_type(typeof(n), Int64))
+    for k in 2:max_n(typeof(n))
         term = zn/oftype(real(z), k)^n
         !isfinite(term) && break
         old_sum = sum
@@ -310,3 +310,12 @@ function li_series_taylor(n::Integer, z::ComplexOrReal)
 
     sum
 end
+
+# returns upper bound on iteration index
+function max_n(::Type{T}) where T
+    if T in (Int8, Int16, Int32, Int64, Int128)
+        typemax(promote_type(T, Int64))
+    else
+        typemax(Int64)
+    end
+end
diff --git a/test/Li.jl b/test/Li.jl
index 25f5e99..a98967b 100644
--- a/test/Li.jl
+++ b/test/Li.jl
@@ -40,6 +40,7 @@ end
                     (n > typemax(TN) || n < typemin(TN)) && continue
                     test_function_on_data(z -> PolyLog.reli(TN(n), z), map(T, real_data), ep, ep)
                 end
+                test_function_on_data(z -> PolyLog.reli(big(n), z), map(T, real_data), ep, ep)
             end
         end
 
@@ -52,6 +53,7 @@ end
                     (n > typemax(TN) || n < typemin(TN)) && continue
                     test_function_on_data(z -> PolyLog.li(TN(n), z), map(Complex{T}, complex_data), ep, ep)
                 end
+                test_function_on_data(z -> PolyLog.li(big(n), z), map(Complex{T}, complex_data), ep, ep)
             end
         end