Author: Mathieu Lafon <firstname.lastname@example.org> State: Draft Type: Project Created: 05-May-2017 Tcl-Version: 8.7 Vote: Done Post-History: Tcl-Branch: info-linkedname Vote-Summary: Rejected 2/2/3 Votes-For: DKF, JN Votes-Against: KBK, DGP Votes-Present: BG, FV, SL Vote-Comments: feature provides insufficient information to be useful, and cannot work in way suitable to solve rationale; please rethink it (talk to TCT to help resolve)
This TIP proposes to improve link variable introspection by providing a new info linkedname command.
This TIP is related to discussions about  and the -upvar extended argument specifier. Adding an intropsection command to get the name of the variable linked to is more Tcl-ish than automatically adding a local variable with the linked name. The proposed command is not restricted to  usage as this can also be used for a link variable created by other means, using the upvar command for example.
Specification of the Proposed Change
There should be a new subcommand of info created with the following syntax:
info linkedname varname
The varname should be the name of a variable that has been linked to another variable (e.g., with upvar, global, variable or namespace upvar), and the result of the command will be the name of the variable linked to.
The reference implementation is available in the info-linkedname branch.
The code is licensed under the BSD license.
Depending on the linked variable, the name is found using different methods:
The name of a variable present in a hash table (globals, local variables created at runtime, ...) is retrieved using the hash key;
The name of an array element is built using the name of the array and the index name, retrieved using the hash key. A new field is added to the TclVarHashTable sructure to access the related array variable from the array element;
The name of a compiled local variable is searched in current or upper call frames.
This document has been placed in the public domain.