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* SI-7983 Fix regression in implicit divergence checkingJason Zaugg2013-11-191-0/+31
As seen in Slick. Regressed in 039b1cb1a5b8. In that commit, a call to `normalize` was replaced with `dealiasWiden` as part of a broad sweeping change. However, while the latter does less than the former with regards to eta expansion ofhigher kinded type refs (the motivation of that commit), it also does more when it comes to singleton types: they are widened to the underlying type. This was widening away `SingleType(<<package a.b>>, <<package c>>)` before the special case assiging that type component a complexity of zero could kick in. In the test case, extracted from Slick, this meant that the divergence check would consider that the second type below to outrank the first in the complexity measure, and abort the implicit search. Shape[?, ? (Coffees, Coffees), ?] Shape[DivergenceTest.this.Flat, ?, Coffees, ?] After this change, the number of packages enclosing `DivergenceTest` no longer has a bearing on the complexity score of the type. Here's how the race was run before hand: complexity(<noprefix>): 0 complexity(<root>): 1 complexity(foo.type): 2 complexity(foo.bar.type): 3 complexity(foo.bar.baz.type): 4 complexity(DivergenceTest.this.type): 5 complexity(<noprefix>): 0 complexity(<root>): 1 complexity(foo.type): 2 complexity(foo.bar.type): 3 complexity(foo.bar.baz.type): 4 complexity(DivergenceTest.this.type): 5 complexity(DivergenceTest.this.Flat): 6 complexity(<noprefix>): 0 complexity(<root>): 1 complexity(scala.type): 2 complexity(Int): 3 complexity(?): 1 complexity(DivergenceTest.this.Shape2[DivergenceTest.this.Flat,Int,?]): 16 complexity(<noprefix>): 0 complexity(<root>): 1 complexity(foo.type): 2 complexity(foo.bar.type): 3 complexity(foo.bar.baz.type): 4 complexity(DivergenceTest.this.type): 5 complexity(?): 1 complexity(<noprefix>): 0 complexity(<root>): 1 complexity(scala.type): 2 complexity(<noprefix>): 0 complexity(Coffees): 1 complexity(<noprefix>): 0 complexity(<root>): 1 complexity(scala.type): 2 complexity(Int): 3 complexity((Coffees, Int)): 7 complexity(?): 1 complexity(DivergenceTest.this.Shape2[?,(Coffees, Int),?]): 15 dominates(DivergenceTest.this.Shape2[_ <: DivergenceTest.this.Flat, Int, U2], DivergenceTest.this.Shape2[_ <: Level, (Coffees, Int), U1]): true And afterwards: complexity(DivergenceTest.this.type): 1 complexity(DivergenceTest.this.type): 1 complexity(DivergenceTest.this.Flat): 2 complexity(scala.type): 1 complexity(Int): 2 complexity(?): 1 complexity(DivergenceTest.this.Shape2[DivergenceTest.this.Flat,Int,?]): 7 complexity(DivergenceTest.this.type): 1 complexity(?): 1 complexity(scala.type): 1 complexity(<noprefix>): 0 complexity(Coffees): 1 complexity(scala.type): 1 complexity(Int): 2 complexity((Coffees, Int)): 5 complexity(?): 1 complexity(DivergenceTest.this.Shape2[?,(Coffees, Int),?]): 9 dominates(DivergenceTest.this.Shape2[_ <: DivergenceTest.this.Flat, Int, U2], DivergenceTest.this.Shape2[_ <: Level, (Coffees, Int), U1]): false Notice that even in the after shot, `scala.Int` has a complexity of 2. It should be 1; this will be fixed in a separate commit.