cmd/kfulint: type checking error on stdlib packages

[quasilyte]

Many stdlib packages cause linter to give up with type checking error.
Most likely, it's because we run Check incorrectly (maybe we should consider build tags or something).

Here is output for math package:

./bin/kfulint -dir=$GOROOT/src/math
skip math: type check error: $GOROOTsrc/math/sincos_386.go:13:6: Sincos redeclared in this block
skip math_test: type check error: $GOROOTsrc/math/all_test.go:3557:7: undeclared name: SqrtGo

There are many other packages with similar problem:

• runtime (re-definitions of symbols)
• net (imports "C")
• net/http (undeclared name)

Other peculiar errors:

bufio:
scan_test.go:408:10: invalid operation: scanner (variable of type *bufio.Scanner) has no field or method MaxTokenSize

bytes:
bytes_test.go:577:31: undeclared name: EqualPortable

context:
context/x_test.go:29:58: undeclared name: XTestDeadlineExceededSupportsTimeout

crypto:
ase/cipher_ppc64le.go:27:6: encryptBlockAsm redeclared in this block
crypto/rand/rand_js.go:9:8: could not import syscall/js (can't find import: "syscall/js")
rc4/rc4_asm.go:13:18: method XORKeyStream already declared for type Cipher struct{s [256]uint32; i uint8; j uint8}
x509/root_darwin_arm_gen.go:38:6: main redeclared in this block
x509/root_cgo_darwin.go:221:8: could not import C (can't find import: "C")

These issues may be related or not.
This needs investigation.

[fexolm]

It might be because we don't handle packages. So some types from other packages seems undeclarated.

[quasilyte]

It's not very urgent, but we must fix this.