wcc: structlit repeat-fill dim off the stamped tinfo (rule 13)

cgstructlitfill's `...` total read only an N_INTLIT dim node, so a
def-dimensioned [N]T struct field under-filled: elements 1..N-1 kept
the zero-fill, silently, wwstage only (cstage and the tn twin read
the stamped array length). Read tichase(fi.tnode.type_).alen first;
the surface node stays as the fallback for unstamped shapes.

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1749;
+def corpuscount: i32 = 1750;
 def errorcount: i32 = 349;
 def compilecount: i32 = 21;
 def runcount: i32 = 209;
-def runexitcount: i32 = 1170;
+def runexitcount: i32 = 1171;
-def nativecount: i32 = 3498;
+def nativecount: i32 = 3500;
-def corpushash: str = "616b3e7f4fca31cb99409c58a29ac73623c997967ddd57651a1370c2c2e2be6a";
+def corpushash: str = "d52fa0df91c89bf51bca70045a2dbf39d5012ac03bf687e231240dc1c5b3fc53";
 
 type directive = enum i32 {
 	ERROR = 0,

selfhost/cmd/wcc/cgenutil.ww

@@ -5937,11 +5937,18 @@ fn cgstructlitfill(c: *cgen, si: *structinfo, lit: *syntax.node,
                         };
                         if (repeat) {
                             let total: i32 = idx;
-                            if (fi.tnode.rhs != nil) {
+                            // rule 13: dim off the STAMPED array tinfo, not
+                            // the surface node — an N_INTLIT-only read left a
+                            // def-dimensioned [N]T field under-filled (ww-only
+                            // silent; cstage + the tn twin read stamped alen).
+                            let ftfill: *syntax.tinfo = tichase(fi.tnode.type_: *syntax.tinfo);
+                            if (ftfill != nil && ftfill.kind == syntax.tykind.TY_ARRAY) {
+                                total = ftfill.alen: i32;
+                            } else { if (fi.tnode.rhs != nil) {
                                 if (fi.tnode.rhs.kind == syntax.nkind.N_INTLIT) {
                                     total = fi.tnode.rhs.uval: i32;
                                 };
-                            };
+                            }; };
                             for (idx < total) {
                                 if (mode == 1) {
                                     emitline("\tMOVQ\t");

test/wcc/data/defdim_field_fill/case.ww

@@ -0,0 +1,16 @@
+//ww:run-exit 0
+// structlit `...` repeat-fill on a def-dimensioned [N]T field: the
+// fill total must come off the stamped array tinfo (rule 13). The
+// N_INTLIT-only surface read left elements 1..N-1 zero (ww-only).
+package main;
+def N: int = 4;
+type holder = struct { arr: [N]i64, tail: i64 };
+export fn main() i32 = {
+	let h: holder = holder{ arr = [7...], tail = 9 };
+	if (h.arr[0] != 7) { return 1; };
+	if (h.arr[1] != 7) { return 2; };
+	if (h.arr[2] != 7) { return 3; };
+	if (h.arr[3] != 7) { return 4; };
+	if (h.tail != 9) { return 5; };
+	return 0;
+};