what is walk(fn *Node) for?

[xie cui]

the go tool compile will call walk, what 's effect of this call?

https://github.com/golang/go/blob/master/src/cmd/compile/internal/gc/walk.go#L20

[Jesper Louis Andersen]

From a quick glance that might be wrong:

It looks like the walk function visits an abstract syntax tree (AST) and performs checks for the statics part of the compiler. E.g., it finds unused variables and functions, type-illegal statements and so on. The term "walk" is used as in that it "walks over the tree and visits each node". The purpose is likely to set up the AST in a state where it is well-typed. This simplifies later stages of the compiler as it can assume certain well-formed principles of the AST structure.

On Mon, Jul 20, 2020 at 4:39 AM xie cui <cuiw...@gmail.com> wrote:

the go tool compile will call walk, what 's effect of this call?

https://github.com/golang/go/blob/master/src/cmd/compile/internal/gc/walk.go#L20

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J.

[Keith Randall]

In addition to what Jesper said, the walk pass does a variety of lowerings and optimizations on the ast. For example, it rewrites the builtin `new` to a runtime call, rewrites switches to a tree of `if` statements, etc.