Zcu: extract permanent state from File

Primarily, this commit removes 2 fields from File, relying on the data
being stored in the `files` field, with the key as the path digest, and
the value as the struct decl corresponding to the File. This table is
serialized into the compiler state that survives between incremental
updates.

Meanwhile, the File struct remains ephemeral data that can be
reconstructed the first time it is needed by the compiler process, as
well as operated on by independent worker threads.

A key outcome of this commit is that there is now a stable index that
can be used to refer to a File. This will be needed when serializing
error messages to survive incremental compilation updates.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/InternPool.zig b/src/InternPool.zig
index c6b27acaf3..e79de26516 100644
--- a/src/InternPool.zig
+++ b/src/InternPool.zig
@@ -123,9 +123,14 @@ pub const TrackedInst = extern struct {
     };
 };
 
-pub fn trackZir(ip: *InternPool, gpa: Allocator, file: *Module.File, inst: Zir.Inst.Index) Allocator.Error!TrackedInst.Index {
+pub fn trackZir(
+    ip: *InternPool,
+    gpa: Allocator,
+    path_digest: Cache.BinDigest,
+    inst: Zir.Inst.Index,
+) Allocator.Error!TrackedInst.Index {
     const key: TrackedInst = .{
-        .path_digest = file.path_digest,
+        .path_digest = path_digest,
         .inst = inst,
     };
     const gop = try ip.tracked_insts.getOrPut(gpa, key);