InternPool: safer enum API

The key changes in this commit are:

```diff
-        names: []const NullTerminatedString,
+        names: NullTerminatedString.Slice,
-        values: []const Index,
+        values: Index.Slice,
```

Which eliminates the slices from `InternPool.Key.EnumType` and replaces
them with structs that contain `start` and `len` indexes. This makes the
lifetime of `EnumType` change from expiring with updates to InternPool,
to expiring when the InternPool is garbage-collected, which is currently
never.

This is gearing up for a larger change I started working on locally
which moves union types into InternPool.

As a bonus, I fixed some unnecessary instances of `@as`.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/link/Dwarf.zig b/src/link/Dwarf.zig
index 6b7744644e..b2ca85467c 100644
--- a/src/link/Dwarf.zig
+++ b/src/link/Dwarf.zig
@@ -388,9 +388,10 @@ pub const DeclState = struct {
                 try ty.print(dbg_info_buffer.writer(), mod);
                 try dbg_info_buffer.append(0);
 
-                const enum_type = mod.intern_pool.indexToKey(ty.ip_index).enum_type;
-                for (enum_type.names, 0..) |field_name_index, field_i| {
-                    const field_name = mod.intern_pool.stringToSlice(field_name_index);
+                const ip = &mod.intern_pool;
+                const enum_type = ip.indexToKey(ty.ip_index).enum_type;
+                for (enum_type.names.get(ip), 0..) |field_name_index, field_i| {
+                    const field_name = ip.stringToSlice(field_name_index);
                     // DW.AT.enumerator
                     try dbg_info_buffer.ensureUnusedCapacity(field_name.len + 2 + @sizeOf(u64));
                     dbg_info_buffer.appendAssumeCapacity(@intFromEnum(AbbrevKind.enum_variant));
@@ -400,7 +401,7 @@ pub const DeclState = struct {
                     // DW.AT.const_value, DW.FORM.data8
                     const value: u64 = value: {
                         if (enum_type.values.len == 0) break :value field_i; // auto-numbered
-                        const value = enum_type.values[field_i];
+                        const value = enum_type.values.get(ip)[field_i];
                         // TODO do not assume a 64bit enum value - could be bigger.
                         // See https://github.com/ziglang/zig/issues/645
                         const field_int_val = try value.toValue().intFromEnum(ty, mod);