core.demangle: add test cases for back references

Author: rainers

src/core/demangle.d

@@ -2074,7 +2074,20 @@ version(unittest)
         ["_D5bug145Class3barMFNjZPv", "return void* bug14.Class.bar()"],
         ["_D5bug143fooFMPvZPv", "void* bug14.foo(scope void*)"],
         ["_D5bug143barFMNkPvZPv", "void* bug14.bar(scope return void*)"],
+        
+        // back references
+        ["_D4core4stdc5errnoQGFZi", "int core.stdc.errno.errno()"], // identifier back reference
+        ["_D4testFS10structnameQ1dZb", "bool test(structname, structname)"], // type back reference
+        ["_D4testFS3pkg10structname5innerSQL2DZb", "bool test(pkg.structname.inner, pkg.structname)"], // symbol back reference
+        // 1.s.s.foo from https://issues.dlang.org/show_bug.cgi?id=15831
+        ["_D13testexpansion44__T1sTS13testexpansion8__T1sTiZ1sFiZ6ResultZ1sFS13testexpansion8__T1sTiZ1sFiZ6ResultZ6Result3fooMFNaNfZv",
+         "pure @safe void testexpansion.s!(testexpansion.s!(int).s(int).Result).s(testexpansion.s!(int).s(int).Result).Result.foo()"],
+        ["_D13testexpansion__T1sTSQ2C__TQ1ATiZQ1GFiZ6ResultZQ3AFQ3bZQ1G3fooMFNaNfZv",
+         "pure @safe void testexpansion.s!(testexpansion.s!(int).s(int).Result).s(testexpansion.s!(int).s(int).Result).Result.foo()"],
+        ["_D2rt4util9container5treap__T5TreapTS2gc11gcinterface4RootZQ3A6insertMFNbNiPSQP7F4NodeQ5aZQ1f",
+         "nothrow @nogc rt.util.container.treap.Treap!(gc.gcinterface.Root).Treap.Node* rt.util.container.treap.Treap!(gc.gcinterface.Root).Treap.insert(rt.util.container.treap.Treap!(gc.gcinterface.Root).Treap.Node*, gc.gcinterface.Root)" ],
     ];
+    
 
     template staticIota(int x)
     {