stage2: fix contents hash computation

during an incremental update change detection,
the function call to get the old contents hash took place
after mangling the old ZIR index, making it access the wrong
array index.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/Module.zig b/src/Module.zig
index d78b9c95e6..e1b4e0b4e2 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -2436,6 +2436,7 @@ fn updateZirRefs(gpa: *Allocator, file: *Scope.File, old_zir: Zir) !UpdateChange
         // Anonymous decls and the root decl have this set to 0. We still need
         // to walk them but we do not need to modify this value.
         if (decl.zir_decl_index != 0) {
+            const old_hash = decl.contentsHashZir(old_zir);
             decl.zir_decl_index = extra_map.get(decl.zir_decl_index) orelse {
                 try deleted_decls.append(gpa, decl);
                 continue;
@@ -2446,7 +2447,6 @@ fn updateZirRefs(gpa: *Allocator, file: *Scope.File, old_zir: Zir) !UpdateChange
             };
             decl.name = new_zir.nullTerminatedString(new_name_index).ptr;
 
-            const old_hash = decl.contentsHashZir(old_zir);
             const new_hash = decl.contentsHashZir(new_zir);
             if (!std.zig.srcHashEql(old_hash, new_hash)) {
                 try outdated_decls.append(gpa, decl);