wcc: #99 alias-of-tuple — chase TY_NAMED in tuple coercion (cstage) + param spill (wwstage)

type pair = (int, int); let x: pair = (3, 4) -- an alias of a tuple
initialized from an untyped literal, and passing such a value to a fn --
was a both-stage bug, mirror-twins of the same TY_NAMED-not-chased root:

cstage CHECKER over-rejected the init (not assignable to declared pair):
type.c's tuple-assignable arm gated on the un-chased dst kind, so a
TY_NAMED alias skipped the per-element untyped->int coercion the direct
tuple path applies. Fix: chase TY_NAMED both sides (mirrors the #258
slice-borrow arm). Direct and typed-alias tuples already worked; only
alias+untyped was rejected.

wwstage CGEN dropped the second word of an alias-tuple fn-arg: the
tuple-param spill at cgendecl.ww gated on the syntactic N_TTUPLE, so an
alias param (N_TNAME) fell to the scalar path and spilled one slot ->
t.1 read frame garbage. Fix: chase the alias via aliaslookup to the
resolved N_TTUPLE and spill all its slots. cstage cgen was already
correct -- the bug was checker-only there. Converges cs==ww byte-id.

One commit: same construct, the two halves must ship together (either
alone leaves cs!=ww). test/wcc/826 (init/fn-arg/return, 2-field byte-id);
test/wcc/944 4 rows graduated err->run-correct. byte-id 990-997 8/8.

selfhost/cmd/w6c/main.combined.ww

@@ -37878,7 +37878,22 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				p = p.next;
 				continue;
 			};
-			if (p.lhs != nil) { if (p.lhs.kind == nkind.N_TTUPLE) {
+			// #99: chase a TY_NAMED alias (multi-level) to its
+			// underlying tuple — the param twin of the cstage type.c
+			// type_chase_named tuple-arm. A bare (i64,i64) is N_TTUPLE
+			// (no chase); `type tp=(i64,i64)` is an N_TNAME resolved via
+			// aliaslookup. Without the chase the alias fell to the scalar
+			// path → 1 slot, SI dropped, t.1 garbage. Slot size + element
+			// walk source the RESOLVED node; localadd keeps the declared
+			// p.lhs so field reads chase identically to cstage (byte-id).
+			let tt99: *node = nil;
+			if (p.lhs != nil) {
+				tt99 = p.lhs;
+				for (tt99 != nil && tt99.kind == nkind.N_TNAME) {
+					tt99 = aliaslookup(c, tt99.str);
+				};
+			};
+			if (p.lhs != nil) { if (tt99 != nil && tt99.kind == nkind.N_TTUPLE) {
 				// #163: tuple PARAM receive (param twin of #164's
 				// return). Walk the tuple's elements over the SysV
 				// arg cursor — a float reads its XMM (X0..X7),
@@ -37890,7 +37905,7 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				// partial-spill stitch is out of scope (twin of #164).
 				let off: i32 = localadd(c, nm, slotsize(c, p.lhs), p.lhs);
 				let eoff: i32 = 0;
-				let te: *node = p.lhs.list;
+				let te: *node = tt99.list;
 				for (te != nil) {
 					let et: *node = te.lhs;
 					if (isfloattype(c, et)) {

selfhost/cmd/wcc/cgendecl.ww

@@ -103,7 +103,22 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				p = p.next;
 				continue;
 			};
-			if (p.lhs != nil) { if (p.lhs.kind == nkind.N_TTUPLE) {
+			// #99: chase a TY_NAMED alias (multi-level) to its
+			// underlying tuple — the param twin of the cstage type.c
+			// type_chase_named tuple-arm. A bare (i64,i64) is N_TTUPLE
+			// (no chase); `type tp=(i64,i64)` is an N_TNAME resolved via
+			// aliaslookup. Without the chase the alias fell to the scalar
+			// path → 1 slot, SI dropped, t.1 garbage. Slot size + element
+			// walk source the RESOLVED node; localadd keeps the declared
+			// p.lhs so field reads chase identically to cstage (byte-id).
+			let tt99: *node = nil;
+			if (p.lhs != nil) {
+				tt99 = p.lhs;
+				for (tt99 != nil && tt99.kind == nkind.N_TNAME) {
+					tt99 = aliaslookup(c, tt99.str);
+				};
+			};
+			if (p.lhs != nil) { if (tt99 != nil && tt99.kind == nkind.N_TTUPLE) {
 				// #163: tuple PARAM receive (param twin of #164's
 				// return). Walk the tuple's elements over the SysV
 				// arg cursor — a float reads its XMM (X0..X7),
@@ -115,7 +130,7 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				// partial-spill stitch is out of scope (twin of #164).
 				let off: i32 = localadd(c, nm, slotsize(c, p.lhs), p.lhs);
 				let eoff: i32 = 0;
-				let te: *node = p.lhs.list;
+				let te: *node = tt99.list;
 				for (te != nil) {
 					let et: *node = te.lhs;
 					if (isfloattype(c, et)) {

selfhost/cmd/wwdump/main.combined.ww

@@ -37878,7 +37878,22 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				p = p.next;
 				continue;
 			};
-			if (p.lhs != nil) { if (p.lhs.kind == nkind.N_TTUPLE) {
+			// #99: chase a TY_NAMED alias (multi-level) to its
+			// underlying tuple — the param twin of the cstage type.c
+			// type_chase_named tuple-arm. A bare (i64,i64) is N_TTUPLE
+			// (no chase); `type tp=(i64,i64)` is an N_TNAME resolved via
+			// aliaslookup. Without the chase the alias fell to the scalar
+			// path → 1 slot, SI dropped, t.1 garbage. Slot size + element
+			// walk source the RESOLVED node; localadd keeps the declared
+			// p.lhs so field reads chase identically to cstage (byte-id).
+			let tt99: *node = nil;
+			if (p.lhs != nil) {
+				tt99 = p.lhs;
+				for (tt99 != nil && tt99.kind == nkind.N_TNAME) {
+					tt99 = aliaslookup(c, tt99.str);
+				};
+			};
+			if (p.lhs != nil) { if (tt99 != nil && tt99.kind == nkind.N_TTUPLE) {
 				// #163: tuple PARAM receive (param twin of #164's
 				// return). Walk the tuple's elements over the SysV
 				// arg cursor — a float reads its XMM (X0..X7),
@@ -37890,7 +37905,7 @@ fn cgfnparams(c: *cgen, params: *node) void = {
 				// partial-spill stitch is out of scope (twin of #164).
 				let off: i32 = localadd(c, nm, slotsize(c, p.lhs), p.lhs);
 				let eoff: i32 = 0;
-				let te: *node = p.lhs.list;
+				let te: *node = tt99.list;
 				for (te != nil) {
 					let et: *node = te.lhs;
 					if (isfloattype(c, et)) {