More efficient float(T) for rationals and big*, works with Irrational (#21219)

Author: giordano

base/complex.jl

@@ -33,6 +33,9 @@ promote_rule(::Type{Complex{T}}, ::Type{Complex{S}}) where {T<:Real,S<:Real} =
 
 widen(::Type{Complex{T}}) where {T} = Complex{widen(T)}
 
+float(::Type{Complex{T}}) where {T<:AbstractFloat} = Complex{T}
+float(::Type{Complex{T}}) where {T} = Complex{float(T)}
+
 """
     real(z)
 

base/float.jl

@@ -272,6 +272,7 @@ Float64
 ```
 """
 float(::Type{T}) where {T<:Number} = typeof(float(zero(T)))
+float(::Type{T}) where {T<:AbstractFloat} = T
 
 for Ti in (Int8, Int16, Int32, Int64)
     @eval begin

base/irrationals.jl

@@ -37,6 +37,8 @@ convert(::Type{Rational{BigInt}}, x::Irrational) = throw(ArgumentError("Cannot c
     end
 end
 
+float(::Type{<:Irrational}) = Float64
+
 ==(::Irrational{s}, ::Irrational{s}) where {s} = true
 ==(::Irrational, ::Irrational) = false
 

base/mpfr.jl

@@ -10,7 +10,7 @@ import
     Base: (*), +, -, /, <, <=, ==, >, >=, ^, ceil, cmp, convert, copysign, div,
         exp, exp2, exponent, factorial, floor, fma, hypot, isinteger,
         isfinite, isinf, isnan, ldexp, log, log2, log10, max, min, mod, modf,
-        nextfloat, prevfloat, promote_rule, rem, rem2pi, round, show,
+        nextfloat, prevfloat, promote_rule, rem, rem2pi, round, show, float,
         sum, sqrt, string, print, trunc, precision, exp10, expm1,
         gamma, lgamma, log1p,
         eps, signbit, sin, cos, tan, sec, csc, cot, acos, asin, atan,
@@ -118,6 +118,8 @@ end
 convert(::Type{Rational}, x::BigFloat) = convert(Rational{BigInt}, x)
 convert(::Type{AbstractFloat}, x::BigInt) = BigFloat(x)
 
+float(::Type{BigInt}) = BigFloat
+
 # generic constructor with arbitrary precision:
 """
     BigFloat(x, prec::Int)

base/rational.jl

@@ -429,3 +429,5 @@ iszero(x::Rational) = iszero(numerator(x))
 function lerpi(j::Integer, d::Integer, a::Rational, b::Rational)
     ((d-j)*a)/d + (j*b)/d
 end
+
+float{T<:Integer}(::Type{Rational{T}}) = float(T)

test/floatfuncs.jl

@@ -68,3 +68,10 @@ for elty in (Float32,Float64)
         @test round.(elty2,A) == fill(round(elty2,x),(10,10,10))
     end
 end
+
+@testset "Types" begin
+    for x in (Int16(0), 1, 2f0, pi, 3//4, big(5//6), 7.8, big(9), big(e))
+        @test float(typeof(x)) == typeof(float(x))
+        @test float(typeof(complex(x, x))) == typeof(float(complex(x, x)))
+    end
+end