this.type in function types is sometimes misinterpreted to mean "this function" instead of "this class", leading to crash with infinite recursive type #23111
Description
Compiler version
3.7.1-RC1
Minimized code
This fails with a reasonable error:
trait A:
def bar: (a: Int, b: Int) => A.this.type = x => ???[error] ./try/foo.scala:2:46
[error] Wrong number of parameters, expected: 2
[error] def bar: (a: Int, b: Int) => A.this.type = x => ???
[error] ^^^^^^^^... but if I replace A.this.type by this.type, things go crazy:
trait A:
def bar: (a: Int, b: Int) => this.type = x => ???[error] ./try/foo.scala:2:44
[error] Missing parameter type
[error]
[error] I could not infer the type of the parameter x
[error] Expected type for the whole anonymous function:
[error] {z1 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z2 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z3 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z4 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z5 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z6 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z7 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z8 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z9 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z10 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z11 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z12 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z13 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z14 => (a: Int, b: Int) =>
[error] (z1 :
[error] {z15 => (a: Int, b: Int
[error] ) =>
[error] (z1 :
[error] {z16 => (a: Int, b:
[error] Int) =>
[error] (z1 :
[error] {z17 => (
[error] a: Int, b: Int
[error] ) =>
[error] (z1 :
[error] {z18 => (
[error] a: Int, b
[error] : Int) =>
[error] (z1 :
[error] {z19 =>
[error] (
[error] a: Int
[error] ,
[error] b: Int)
[error] =>
[error] (z1 :
[error] {z20
[error] =>
[error] (
[error] a
[error] :
[error] ...
[error] ,
[error] b
[error] :
[error] ...
[error] )
[error] =>
[error]
[error] (
[error] ...
[error] :
[error] ...
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] )
[error] }
[error] def bar: (a: Int, b: Int) => this.type = x => ???
[error] ^Expectation
Clearly this.type refers to A.this.type here, so the two pieces of code should behave in the same way, and not attempt to create an infinitely recursive type.