fix power_by_squaring: use promote instead of type inference (#55634)

Fixes #53504

Fixes #55633

Author: nsajko

base/intfuncs.jl

@@ -298,7 +298,11 @@ function invmod(n::T) where {T<:BitInteger}
 end
 
 # ^ for any x supporting *
-to_power_type(x) = convert(Base._return_type(*, Tuple{typeof(x), typeof(x)}), x)
+function to_power_type(x::Number)
+    T = promote_type(typeof(x), typeof(one(x)), typeof(x*x))
+    convert(T, x)
+end
+to_power_type(x) = oftype(x*x, x)
 @noinline throw_domerr_powbysq(::Any, p) = throw(DomainError(p, LazyString(
     "Cannot raise an integer x to a negative power ", p, ".",
     "\nConvert input to float.")))

test/math.jl

@@ -1498,6 +1498,28 @@ end
     n = Int64(1024 / log2(E))
     @test E^n == Inf
     @test E^float(n) == Inf
+
+    # #55633
+    struct Issue55633_1 <: Number end
+    struct Issue55633_3 <: Number end
+    struct Issue55633_9 <: Number end
+    Base.one(::Issue55633_3) = Issue55633_1()
+    Base.:(*)(::Issue55633_3, ::Issue55633_3) = Issue55633_9()
+    Base.promote_rule(::Type{Issue55633_1}, ::Type{Issue55633_3}) = Int
+    Base.promote_rule(::Type{Issue55633_3}, ::Type{Issue55633_9}) = Int
+    Base.promote_rule(::Type{Issue55633_1}, ::Type{Issue55633_9}) = Int
+    Base.promote_rule(::Type{Issue55633_1}, ::Type{Int}) = Int
+    Base.promote_rule(::Type{Issue55633_3}, ::Type{Int}) = Int
+    Base.promote_rule(::Type{Issue55633_9}, ::Type{Int}) = Int
+    Base.convert(::Type{Int}, ::Issue55633_1) = 1
+    Base.convert(::Type{Int}, ::Issue55633_3) = 3
+    Base.convert(::Type{Int}, ::Issue55633_9) = 9
+    for x ∈ (im, pi, Issue55633_3())
+        p = promote(one(x), x, x*x)
+        for y ∈ 0:2
+            @test all((t -> ===(t...)), zip(x^y, p[y + 1]))
+        end
+    end
 end
 
 # Test that sqrt behaves correctly and doesn't exhibit fp80 double rounding.