re PR d/90602 (ICE: null field)

	PR d/90602
d/dmd: Merge upstream dmd 420cce2a6

Fixes internal compiler error during CTFE.

Reviewed-on: https://github.com/dlang/dmd/pull/9997

From-SVN: r272342

gcc/d/dmd/MERGE

-c74e624c9a0a9e7e39f96b2f005f86e123df56c9
+420cce2a654f14b8de4a75cbb5d4203fce8d4e0f
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/dmd repository.

gcc/d/dmd/dinterpret.c

@@ -6053,9 +6053,16 @@ public:
         result = (*se->elements)[i];
         if (!result)
         {
-            e->error("Internal Compiler Error: null field %s", v->toChars());
-            result = CTFEExp::cantexp;
-            return;
+            // https://issues.dlang.org/show_bug.cgi?id=19897
+            // Zero-length fields don't have an initializer.
+            if (v->type->size() == 0)
+                result = voidInitLiteral(e->type, v).copy();
+            else
+            {
+                e->error("Internal Compiler Error: null field %s", v->toChars());
+                result = CTFEExp::cantexp;
+                return;
+            }
         }
         if (result->op == TOKvoid)
         {

gcc/testsuite/gdc.test/fail_compilation/fail19897.d

+// PERMUTE_ARGS:
+/*
+TEST_OUTPUT
+---
+fail_compilation/fail19897.d(10): Error: cannot implicitly convert expression `[]` of type `const(char[0])` to `const(char)`
+---
+*/
+struct S
+{
+    char[0] x;
+}
+const a = S('a');
+const char c = a.x;