RemoveRelationCopies transformation removes intermediate eqrel

[langston-barrett]

Consider the following program:

.decl r(a: number, b: number)
.decl s(a: number, b: number) eqrel
.decl t(a: number, b: number)

r(1, 2).
s(a, b) :- r(a, b).
t(a, b) :- s(a, b).

.output t(IO=stdout)

The expected output is (1, 2), (2, 1), because s is an eqrel. However, --show=transformed-datalog reveals:

.decl r(a:number, b:number) 
.decl t(a:number, b:number) 
r(1,2).

t(a,b) :- 
   r(a,b).

This transformation is not valid, and the output of the program is

---------------
t
===============
1	2
===============

souffle --version                         
Souffle: 2.2-129-gfce85d9ec(32bit Domains)

[langston-barrett]

The transformer at fault appears to be RemoveRelationCopiesTransformer:

souffle --disable-transformers=RemoveRelationCopiesTransformer --show=transformed-datalog test.dl

yields

.decl r(a:number, b:number) 
.decl s(a:number, b:number) eqrel
.decl t(a:number, b:number) 
r(1,2).

s(a,b) :- 
   r(a,b).

t(a,b) :- 
   s(a,b).

and evaluation yields

---------------                                                               
t
===============
1	1
1	2
2	1
2	2
===============