Revert "Optimize findall(f, ::AbstractArray{Bool}) (#42202)" (#51039)

This reverts commit 4c4c94f. (Except
keeps the tests and adds a new one)

fixes #46425

(cherry picked from commit defe187)

base/array.jl

@@ -2487,42 +2487,19 @@ function findall(A)
 end
 
 # Allocating result upfront is faster (possible only when collection can be iterated twice)
-function _findall(f::Function, A::AbstractArray{Bool})
-    n = count(f, A)
+function findall(A::AbstractArray{Bool})
+    n = count(A)
     I = Vector{eltype(keys(A))}(undef, n)
-    isempty(I) && return I
-    _findall(f, I, A)
-end
-
-function _findall(f::Function, I::Vector, A::AbstractArray{Bool})
-    cnt = 1
-    len = length(I)
-    for (k, v) in pairs(A)
-        @inbounds I[cnt] = k
-        cnt += f(v)
-        cnt > len && return I
-    end
-    # In case of impure f, this line could potentially be hit. In that case,
-    # we can't assume I is the correct length.
-    resize!(I, cnt - 1)
-end
-
-function _findall(f::Function, I::Vector, A::AbstractVector{Bool})
-    i = firstindex(A)
     cnt = 1
-    len = length(I)
-    while cnt ≤ len
-        @inbounds I[cnt] = i
-        cnt += f(@inbounds A[i])
-        i = nextind(A, i)
+    for (i,a) in pairs(A)
+        if a
+            I[cnt] = i
+            cnt += 1
+        end
     end
-    cnt - 1 == len ? I : resize!(I, cnt - 1)
+    I
 end
 
-findall(f::Function, A::AbstractArray{Bool}) = _findall(f, A)
-findall(f::Fix2{typeof(in)}, A::AbstractArray{Bool}) = _findall(f, A)
-findall(A::AbstractArray{Bool}) = _findall(identity, A)
-
 findall(x::Bool) = x ? [1] : Vector{Int}()
 findall(testf::Function, x::Number) = testf(x) ? [1] : Vector{Int}()
 findall(p::Fix2{typeof(in)}, x::Number) = x in p.x ? [1] : Vector{Int}()

test/arrayops.jl

@@ -604,6 +604,15 @@ end
     @testset "issue 43078" begin
         @test_throws TypeError findall([1])
     end
+
+    @testset "issue #46425" begin
+        counter = 0
+        function pred46425(x)
+            counter += 1
+            counter < 4 && x
+        end
+        @test findall(pred46425, [false, false, true, true]) == [3]
+    end
 end
 @testset "find with Matrix" begin
     A = [1 2 0; 3 4 0]