by raul.san@sent.com:

"go/parser.ParseDir" is not returning an error at parsing files with a keyword
re-declared.
Note: this possible bug also could happens in "parser.ParseFile".

* * *

+ File: foo.go
***
package main

import (
    "go/parser"
    "go/token"
    "log"
)

func main() {
    fset := token.NewFileSet()
    _, err := parser.ParseDir(fset, "data", nil, parser.ParseComments|parser.DeclarationErrors)
    if err != nil {
        log.Fatal(err)
    }
}
***

+ File: data/a.go
***
package main

func Foo() {}
***

+ File: data/b.go
***
package main

func Foo() {}
***

* * *
However, if you try to use the "go tool" build it, it will return such error:

    data$ go build
    ./b.go:3: Foo redeclared in this block
        previous declaration at ./a.go:3

* * *
go version go1.2.1 linux/amd64