function definition overwriting in if statement

[federicoizzo]

Hi everyone, sorry to bother. I encountered a weird behaviour recently, and I wanted to show it.

I define a function in an if statement; it is defined in one way if "flag" is true and in another otherwise. But when I run and the code goes through the first case, the second definition is used even if that code is not passed through at all.

Example: the output of this code

function test_bug_1(flag)
c=987;
if flag
    d(x)=x
else
    d(x)=x-c
end
println(d(1))
end

test_bug_1(true)

The output is -986 instead of 1. If I "correct" the code in the following way it works as intended:

function test_bug_2(flag)
c=987;
if flag
    d1(x)=x
    d=d1
else
    d2(x)=x-c
    d=d2
end
println(d(1))
end

test_bug_2(true)

Output: 1

Here are the info from versioninfo():
julia> versioninfo()
Julia Version 1.2.0
Commit c6da87f (2019-08-20 00:03 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-6.0.1 (ORCJIT, broadwell)

Is this something I should have predicted in some way? Or is something weird happening? I greatly appreciate all the help.

[StefanKarpinski]

Dup of #15602.