gcc/cp/ChangeLog:
PR c++/42225
* pt.c (push_template_decl_real): Set DECL_CONTEXT of template type
parms to their containing template decl.
* typeck.c (comp_template_parms_position): Split this from
structural_comptypes.
(incompatible_template_type_parms_p): Renamed
incompatible_dependent_typedefs_p into this. Change the function to
handle comparison between TEMPLATE_TYPE_PARMs only.
(structural_comptypes): Use comp_template_parms_position in
TEMPLATE_TEMPLATE_PARM and BOUND_TEMPLATE_TEMPLATE_PARM cases.
Use incompatible_template_type_parms_p in TEMPLATE_TYPE_PARM case.
* mangle.c (decl_mangling_context): Template type parms don't have
a mangling context.
* tree.c (cp_set_underlying_type): Set type structural equality
only for TEMPLATE_TYPE_PARMs.
gcc/testsuite/ChangeLog:
PR c++/42225
* g++.dg/template/typedef26.C: New test.