Add literal_pow transformation (#19)

src/OverflowContexts.jl

@@ -3,6 +3,20 @@ module OverflowContexts
 const SignedBitInteger = Union{Int8, Int16, Int32, Int64, Int128}
 const UnsignedBitInteger = Union{UInt8, UInt16, UInt32, UInt64, UInt128}
 
+using Base: BitInteger, promote, afoldl, @_inline_meta
+import Base: literal_pow
+import Base.Checked: checked_neg, checked_add, checked_sub, checked_mul, checked_abs,
+    checked_div, checked_fld, checked_cld, checked_mod, checked_rem
+using Base.Checked: mul_with_overflow
+
+if VERSION ≥ v"1.11-alpha"
+    import Base: power_by_squaring
+    import Base.Checked: checked_pow
+else
+    using Base: throw_domerr_powbysq, to_power_type
+    using Base.Checked: throw_overflowerr_binaryop
+end
+
 include("macros.jl")
 include("checked.jl")
 include("unchecked.jl")

src/checked.jl

@@ -1,16 +1,3 @@
-using Base: BitInteger, promote, afoldl, @_inline_meta
-import Base.Checked: checked_neg, checked_add, checked_sub, checked_mul, checked_abs,
-    checked_div, checked_fld, checked_cld, checked_mod, checked_rem
-using Base.Checked: mul_with_overflow
-
-if VERSION ≥ v"1.11-alpha"
-    import Base: power_by_squaring
-    import Base.Checked: checked_pow
-else
-    using Base: throw_domerr_powbysq, to_power_type
-    using Base.Checked: throw_overflowerr_binaryop
-end
-
 # resolve ambiguity when `-` used as symbol
 checked_negsub(x) = checked_neg(x)
 checked_negsub(x, y) = checked_sub(x, y)
@@ -87,3 +74,19 @@ if VERSION < v"1.11"
         return y
     end    
 end
+
+# adapted from Base intfuncs.jl; negative literal powers promote to floating point
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{0}) = one(x)
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{1}) = x
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{2}) = @checked x * x
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{3}) = @checked x * x * x
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{-1}) = literal_pow(^, x, Val(-1))
+@inline literal_pow(::typeof(checked_pow), x::BitInteger, ::Val{-2}) = literal_pow(^, x, Val(-2))
+
+@inline function literal_pow(f::typeof(checked_pow), x, ::Val{p}) where {p}
+    if p < 0
+        literal_pow(^, x, Val(p))
+    else
+        f(x, p)
+    end
+end

src/macros.jl

@@ -235,12 +235,18 @@ function replace_op!(expr::Expr, op_map::Dict)
                     Expr(:tuple, expr.args[2:end]...)]
             end
         else                                      # arbitrary call
+            op_orig = op
             op = get(op_map, op, op)
             if isexpr(f, :.)
                 f.args[2] = QuoteNode(op)
                 expr.args[1] = f
             else
                 expr.args[1] = op
+                if op_orig == :^ && expr.args[3] isa Integer
+                    # literal_pow transformation
+                    pushfirst!(expr.args, :(Base.literal_pow))
+                    expr.args[4] = :(Val($(expr.args[4])))
+                end
             end
         end
         for i in 2:length(expr.args)

src/saturating.jl

@@ -1,10 +1,3 @@
-import Base: BitInteger
-import Base.Checked: mul_with_overflow
-
-if VERSION ≥ v"1.11-alpha"
-    using Base: power_by_squaring
-end
-
 # resolve ambiguity when `-` used as symbol
 saturating_negsub(x) = saturating_neg(x)
 saturating_negsub(x, y) = saturating_sub(x, y)
@@ -156,3 +149,19 @@ function saturating_mod(x::T, y::T) where T <: SignedBitInteger
 end
 
 saturating_mod(x::T, y::T) where T <: UnsignedBitInteger = @saturating rem(x, y)
+
+# adapted from Base intfuncs.jl; negative literal powers promote to floating point
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{0}) = one(x)
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{1}) = x
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{2}) = @saturating x * x
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{3}) = @saturating x * x * x
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{-1}) = literal_pow(^, x, Val(-1))
+@inline literal_pow(::typeof(saturating_pow), x::BitInteger, ::Val{-2}) = literal_pow(^, x, Val(-2))
+
+@inline function literal_pow(f::typeof(saturating_pow), x, ::Val{p}) where {p}
+    if p < 0
+        literal_pow(^, x, Val(p))
+    else
+        f(x, p)
+    end
+end

src/unchecked.jl

@@ -67,3 +67,6 @@ unchecked_rem(x::T, y::T) where T <: UnsignedBitInteger =
 
 unchecked_mod(x::T, y::T) where T <: SignedBitInteger = x - unchecked_fld(x, y) * y
 unchecked_mod(x::T, y::T) where T <: UnsignedBitInteger = unchecked_rem(x, y)
+
+# adapted from Base intfuncs.jl; negative literal powers promote to floating point
+@inline literal_pow(::typeof(unchecked_pow), x, ::Val{p}) where {p} = literal_pow(^, x, Val(p))

test/runtests.jl

@@ -792,3 +792,9 @@ end
     @test_throws ErrorException @saturating aa * bb'
     @test_throws ErrorException @saturating dd ^ 2
 end
+
+@testset "literal_pow transformation" begin
+    expr = @macroexpand @checked 5 ^ 2
+    @test expr.args[1] == :(Base.literal_pow)
+    @test expr.args[2] == :(OverflowContexts.checked_pow)
+end