Add specialized * for Rational and Integer (#35483)

JuliaLang · Apr 15, 2020 · 07b7237 · 07b7237 · nanosoldier · Apr 15, 2020
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commit 07b7237
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diff --git a/base/rational.jl b/base/rational.jl
@@ -279,6 +279,11 @@ function *(x::Rational, y::Rational)
     xd,yn = divgcd(x.den,y.num)
     checked_mul(xn,yn) // checked_mul(xd,yd)
 end
+function *(x::Rational, y::Integer)
+    xd, yn = divgcd(x.den, y)
+    checked_mul(x.num, yn) // xd
+end
+*(x::Integer, y::Rational) = *(y, x)
 /(x::Rational, y::Rational) = x//y
 /(x::Rational, y::Complex{<:Union{Integer,Rational}}) = x//y
 inv(x::Rational) = Rational(x.den, x.num)

diff --git a/test/rational.jl b/test/rational.jl
@@ -414,11 +414,16 @@ end
         @test rem(q, i) == q - i*div(q, i)
         @test mod(q, i) == q - i*fld(q, i)
     end
+    @test 1//2 * 3 == 3//2
+    @test -3 * (1//2) == -3//2
 
     @test_throws OverflowError UInt(1)//2 - 1
     @test_throws OverflowError 1 - UInt(5)//2
     @test_throws OverflowError 1//typemax(Int64) + 1
     @test_throws OverflowError Int8(1) + Int8(5)//(Int8(127)-Int8(1))
+    @test_throws InexactError UInt(1)//2 * -1
+    @test_throws OverflowError typemax(Int64)//1 * 2
+    @test_throws OverflowError -1//1 * typemin(Int64)
 
     @test Int8(1) + Int8(4)//(Int8(127)-Int8(1)) == Int8(65) // Int8(63)
     @test -Int32(1) // typemax(Int32) - Int32(1) == typemin(Int32) // typemax(Int32)