Bug 1054 – regression: circular aliases cause compiler stack overflow

# alias a b; # alias b a; # # b x; dmd -c a.d -> segfaults # alias a b; # alias b a; dmd -c a.d -> compiles even though it shouldn't test cases: http://dstress.kuehne.cn/nocompile/a/alias_30_G.d http://dstress.kuehne.cn/nocompile/a/alias_30_J.d http://dstress.kuehne.cn/nocompile/a/alias_30_K.d http://dstress.kuehne.cn/nocompile/e/enum_44_E.d

*** Bug 1063 has been marked as a duplicate of this bug. ***

The first case no longer segfaults -- it stack overflows instead, and the second case now generates an error. On DMD1.042, the first case displays: fog.d(2): Error: alias fog.a recursive alias declaration Stack overflow and on DMD2.027, it gets caught in an infinite loop: fog.d(2): Error: alias fog.a recursive alias declaration fog.d(2): Error: alias fog.a recursive alias declaration fog.d(2): Error: alias fog.a recursive alias declaration fog.d(2): Error: alias fog.a recursive alias declaration fog.d(2): Error: alias fog.a recursive alias declaration

This is fixed in DMD2.030, but not in DMD1.045. alias a b; alias b a; a y; --- ice.d(544): Error: alias ice.a recursive alias declaration Stack overflow ----------

Fixed dmd 1.046