nikomatsakis/debruijn.md

Created July 9, 2017 16:09

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Raw

fn foo(x: fn(&T), y: &U)

                fn foo
              x /     \ y
              fn       &
              |        |
              &        U
              |
              T

In the case of the &T type that is part of x, debruijn index of 1 refers to the fn, and 2 refers to the fn foo.

In the case of the &U type that is part of y, debruijn index of 1 refers to the fn foo.

general rule: debruijn index goes upwards in the tree, stopping at each fn (or other place where regions can be bound -- typically functions).