add missing _convert_rounding methods for RoundFromZero (#57802)

Implemented `_convert_rounding` method for `RoundingMode{:FromZero}`
similar to other `_convert_rounding` methods for other rounding modes.

Fix #55820

Co-authored-by: Lilith Orion Hafner <lilithhafner@gmail.com>

Author: RafaelAvelar14

base/rounding.jl

@@ -281,6 +281,15 @@ function _convert_rounding(::Type{T}, x::Real, r::RoundingMode{:ToZero}) where T
         y < x ? nextfloat(y) : y
     end
 end
+function _convert_rounding(::Type{T}, x::Real, r::RoundingMode{:FromZero}) where T<:AbstractFloat
+    y = convert(T,x)::T
+    if x < 0.0
+        y > x ? prevfloat(y) : y
+    else
+        y < x ? nextfloat(y) : y
+    end
+end
+
 
 # Default definitions
 

test/rounding.jl

@@ -495,3 +495,16 @@ end
         end
     end
 end
+
+@testset "Rounding to floating point types with RoundFromZero #55820" begin
+    @testset "Testing float types: $f" for f ∈ (Float16, Float32, Float64, BigFloat)
+        @testset "Testing value types: $t" for t ∈ (Bool, Rational{Int8})
+            @test iszero(f(zero(t), RoundFromZero))
+        end
+    end
+    @test Float16(100000, RoundToZero) === floatmax(Float16)
+    @test Float16(100000, RoundFromZero) === Inf16
+    @test Float16(-100000, RoundToZero) === -floatmax(Float16)
+    @test Float16(-100000, RoundFromZero) === -Inf16
+    @test Float32(nextfloat(0.0), RoundFromZero) === nextfloat(0.0f0)
+end