hclsyntax: Various error messages related to unexpectedly reaching end of file while parsing a delimited subtree will now return specialized messages describing the opening tokens as "unclosed", instead of returning a generic diagnostic that just happens to refer to the empty source range at the end of the file. This gives better feedback when error messages are being presented alongside a source code snippet, as is common in HCL-based applications, because it shows which innermost container the parser was working on when it encountered the error. (#492)
Bugs Fixed
hclsyntax: Upgrading an unknown single value to a list using a splat expression must return unknown (#493)
