From 7a7d0225d9825f0150e797a4ff06f6e56af08458 Mon Sep 17 00:00:00 2001
From: mlugg <mlugg@mlugg.co.uk>
Date: Sat, 5 Aug 2023 10:55:49 +0100
Subject: [PATCH] Sema: detect invalid field stores in tuple initialization

This bug was exposed by the previous commit, since array_init is now
used for tuple parameters.
---
 src/Sema.zig | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 5aeb55ddc3..6752e19b6b 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -19393,13 +19393,14 @@ fn zirArrayInit(
         },
         else => |e| return e,
     };
+    const is_tuple = array_ty.zigTypeTag(mod) == .Struct;
     const sentinel_val = array_ty.sentinel(mod);
 
     const resolved_args = try gpa.alloc(Air.Inst.Ref, args.len - 1 + @intFromBool(sentinel_val != null));
     defer gpa.free(resolved_args);
     for (args[1..], 0..) |arg, i| {
         const resolved_arg = try sema.resolveInst(arg);
-        const elem_ty = if (array_ty.zigTypeTag(mod) == .Struct)
+        const elem_ty = if (is_tuple)
             array_ty.structFieldType(i, mod)
         else
             array_ty.elemType2(mod);
@@ -19412,6 +19413,18 @@ fn zirArrayInit(
             },
             else => return err,
         };
+        if (is_tuple) if (try array_ty.structFieldValueComptime(mod, i)) |field_val| {
+            const init_val = try sema.resolveMaybeUndefVal(resolved_args[i]) orelse {
+                const decl = mod.declPtr(block.src_decl);
+                const elem_src = mod.initSrc(src.node_offset.x, decl, i);
+                return sema.failWithNeededComptime(block, elem_src, "value stored in comptime field must be comptime-known");
+            };
+            if (!field_val.eql(init_val, elem_ty, mod)) {
+                const decl = mod.declPtr(block.src_decl);
+                const elem_src = mod.initSrc(src.node_offset.x, decl, i);
+                return sema.failWithInvalidComptimeFieldStore(block, elem_src, array_ty, i);
+            }
+        };
     }
 
     if (sentinel_val) |some| {