value: hash extern functions

Closes #12766

1 files changed, 6 insertions, 3 deletions

diff --git a/src/value.zig b/src/value.zig
index 50f86c7e79..0580d7cd3c 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -2391,12 +2391,15 @@ pub const Value = extern union {
                 union_obj.val.hash(active_field_ty, hasher, mod);
             },
             .Fn => {
-                const func: *Module.Fn = val.castTag(.function).?.data;
-                // Note that his hashes the *Fn rather than the *Decl. This is
+                // Note that his hashes the *Fn/*ExternFn rather than the *Decl. This is
                 // to differentiate function bodies from function pointers.
                 // This is currently redundant since we already hash the zig type tag
                 // at the top of this function.
-                std.hash.autoHash(hasher, func);
+                if (val.castTag(.function)) |func| {
+                    std.hash.autoHash(hasher, func.data);
+                } else if (val.castTag(.extern_fn)) |func| {
+                    std.hash.autoHash(hasher, func.data);
+                } else unreachable;
             },
             .Frame => {
                 @panic("TODO implement hashing frame values");