From fbc1612d48ff9d4bc3fa723efcf9fc4d3ee81ede Mon Sep 17 00:00:00 2001
From: Sebastian Stock <42280794+sostock@users.noreply.github.com>
Date: Tue, 15 Jun 2021 09:00:56 +0200
Subject: [PATCH] Fix Rational{T} constructor for abstract T (#41229)

(cherry picked from commit e34c77b41d75f5ad7b321de2f876e3a1b3594fc7)
---
 base/rational.jl | 7 ++++---
 test/rational.jl | 4 ++++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/base/rational.jl b/base/rational.jl
index 12b5113e8e475..fd1c9d3ac7f79 100644
--- a/base/rational.jl
+++ b/base/rational.jl
@@ -18,21 +18,22 @@ unsafe_rational(num::T, den::T) where {T<:Integer} = unsafe_rational(T, num, den
 unsafe_rational(num::Integer, den::Integer) = unsafe_rational(promote(num, den)...)
 
 @noinline __throw_rational_argerror_typemin(T) = throw(ArgumentError("invalid rational: denominator can't be typemin($T)"))
-function checked_den(num::T, den::T) where T<:Integer
+function checked_den(::Type{T}, num::T, den::T) where T<:Integer
     if signbit(den)
         den = -den
-        signbit(den) && __throw_rational_argerror_typemin(T)
+        signbit(den) && __throw_rational_argerror_typemin(typeof(den))
         num = -num
     end
     return unsafe_rational(T, num, den)
 end
+checked_den(num::T, den::T) where T<:Integer = checked_den(T, num, den)
 checked_den(num::Integer, den::Integer) = checked_den(promote(num, den)...)
 
 @noinline __throw_rational_argerror_zero(T) = throw(ArgumentError("invalid rational: zero($T)//zero($T)"))
 function Rational{T}(num::Integer, den::Integer) where T<:Integer
     iszero(den) && iszero(num) && __throw_rational_argerror_zero(T)
     num, den = divgcd(num, den)
-    return checked_den(T(num), T(den))
+    return checked_den(T, T(num), T(den))
 end
 
 Rational(n::T, d::T) where {T<:Integer} = Rational{T}(n, d)
diff --git a/test/rational.jl b/test/rational.jl
index d79725baffa7b..0184060bcce87 100644
--- a/test/rational.jl
+++ b/test/rational.jl
@@ -607,3 +607,7 @@ end
 @testset "checked_den with different integer types" begin
     @test Base.checked_den(Int8(4), Int32(8)) == Base.checked_den(Int32(4), Int32(8))
 end
+
+@testset "Rational{T} with non-concrete T (issue #41222)" begin
+    @test @inferred(Rational{Integer}(2,3)) isa Rational{Integer}
+end