Make printing of big(NaN) consistent (#23382)

Author: jw3126

base/mpfr.jl

@@ -895,9 +895,7 @@ end
 setprecision(f::Function, precision::Integer) = setprecision(f, BigFloat, precision)
 
 function string(x::BigFloat)
-    if isnan(x) || isinf(x)
-        return string("BigFloat(", Float64(x), ", ", precision(x), ")")
-    end
+    isfinite(x) || return string(Float64(x))
 
     # In general, the number of decimal places needed to read back the number exactly
     # is, excluding the most significant, ceil(log(10, 2^precision(x)))

test/mpfr.jl

@@ -880,12 +880,6 @@ for prec in (10, 100, 1000)
     end
 end
 
-setprecision(256) do
-    @test string(big(Inf)) == "BigFloat(Inf, 256)"
-    @test string(big(-Inf)) == "BigFloat(-Inf, 256)"
-    @test string(big(NaN)) == "BigFloat(NaN, 256)"
-end
-
 # issue #22758
 if MPFR.version() > v"3.1.5" || "r11590" in MPFR.version().build
     setprecision(2_000_000) do

test/numbers.jl

@@ -3028,9 +3028,14 @@ end
     end
 end
 
-@testset "compact NaN printing" begin
-    @test sprint(io->show(IOContext(io, :compact => true), NaN16)) == "NaN"
-    @test sprint(io->show(IOContext(io, :compact => true), NaN32)) == "NaN"
-    @test sprint(io->show(IOContext(io, :compact => true), NaN64)) == "NaN"
-    @test_broken sprint(io->show(IOContext(io, :compact => true), big(NaN))) == "NaN"
+@testset "printing non finite floats" for T in subtypes(AbstractFloat)
+    for (x, sx) in [(T(NaN), "NaN"),
+                    (-T(NaN), "NaN"),
+                    (T(Inf), "Inf"),
+                    (-T(Inf), "-Inf")]
+        @assert x isa T
+        @test string(x) == sx
+        @test sprint(io -> show(IOContext(io, :compact => true), x)) == sx
+        @test sprint(print, x) == sx
+    end
 end