all: implement changes in Go 1.14, 1.15, 1.16 and 1.17

[gazerro]

These are Commits in Go 1.14 that make changes that may need to be implemented in Scriggo:

• golang/go@e710a1f cmd/compile: report more precise errors about untyped constants

• golang/go@581526c cmd/compile: rewrite untyped constant conversion logic

• golang/go@449b6ab cmd/compile/internal/gc: reword "declared and not used" error message

• golang/go@efd395f cmd/compile: make duplicate index error distinguish arrays and slices

• golang/go@2d1c033 reflect: let StructOf define unexported fields

These are Commits in Go 1.15 that make changes that may need to be implemented in Scriggo:

• golang/go@ffc0573 cmd/compile/internal/syntax: better error when an assignment is used in value context

• golang/go@7802b55 reflect: update Select to panic early on excessive input cases

• golang/go@972df38 runtime: during panic, print value instead of address, if kind is printable

• golang/go@bfb903f cmd/compile/internal/syntax: better scanner error messages

These are Commits in Go 1.16 that make changes that may need to be implemented in Scriggo:

• golang/go@2c95e3a cmd/compile: use clearer error message for stuct literal

• golang/go@806f478 cmd/compile: don't report not enough args error if call is undefined

• golang/go@7ee35cb cmd/compile: be more specific in cannot assign errors

• golang/go@df73945 cmd/compile: make error message involving variadic calls clearer

• golang/go@23573d0 cmd/compile: clearer error when non-bool used as "||" and "&&" operand

• golang/go@2333c62 runtime: use old capacity to decide on append growth regime

These are Commits in Go 1.17 that make changes that may need to be implemented in Scriggo:

• golang/go@1c26843 spec: allow conversion from slice to array ptr

• golang/go@785a8f6 cmd/compile: better error message for invalid untyped operation

[gazerro]

See also issue #795.