AstGen: decouple from Module/Compilation

AstGen is now completely independent from the rest of the compiler. It
ingests an AST tree and produces ZIR code as the output, without
depending on any of the glue code of the compiler.

BRANCH_TODO

@@ -1,6 +1,5 @@
  * implement lazy struct field resolution; don't resolve struct fields until
    they are needed.
- * decouple AstGen from Module, Compilation
  * AstGen threadlocal
  * extern "foo" for vars and for functions
  * namespace decls table can't reference ZIR memory because it can get modified on updates

src/RangeSet.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 const Order = std.math.Order;
 const Value = @import("value.zig").Value;
 const RangeSet = @This();
-const SwitchProngSrc = @import("AstGen.zig").SwitchProngSrc;
+const SwitchProngSrc = @import("Module.zig").SwitchProngSrc;
 
 ranges: std.ArrayList(Range),
 

src/Sema.zig

@@ -63,7 +63,6 @@ const InnerError = Module.InnerError;
 const Decl = Module.Decl;
 const LazySrcLoc = Module.LazySrcLoc;
 const RangeSet = @import("RangeSet.zig");
-const AstGen = @import("AstGen.zig");
 
 pub fn analyzeFnBody(
     sema: *Sema,
@@ -3361,10 +3360,10 @@ fn analyzeSwitch(
     // Validate for duplicate items, missing else prong, and invalid range.
     switch (operand.ty.zigTypeTag()) {
         .Enum => {
-            var seen_fields = try gpa.alloc(?AstGen.SwitchProngSrc, operand.ty.enumFieldCount());
+            var seen_fields = try gpa.alloc(?Module.SwitchProngSrc, operand.ty.enumFieldCount());
             defer gpa.free(seen_fields);
 
-            mem.set(?AstGen.SwitchProngSrc, seen_fields, null);
+            mem.set(?Module.SwitchProngSrc, seen_fields, null);
 
             var extra_index: usize = special.end;
             {
@@ -3989,8 +3988,8 @@ fn resolveSwitchItemVal(
     block: *Scope.Block,
     item_ref: Zir.Inst.Ref,
     switch_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
-    range_expand: AstGen.SwitchProngSrc.RangeExpand,
+    switch_prong_src: Module.SwitchProngSrc,
+    range_expand: Module.SwitchProngSrc.RangeExpand,
 ) InnerError!TypedValue {
     const item = try sema.resolveInst(item_ref);
     // We have to avoid the other helper functions here because we cannot construct a LazySrcLoc
@@ -4014,7 +4013,7 @@ fn validateSwitchRange(
     first_ref: Zir.Inst.Ref,
     last_ref: Zir.Inst.Ref,
     src_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
 ) InnerError!void {
     const first_val = (try sema.resolveSwitchItemVal(block, first_ref, src_node_offset, switch_prong_src, .first)).val;
     const last_val = (try sema.resolveSwitchItemVal(block, last_ref, src_node_offset, switch_prong_src, .last)).val;
@@ -4028,7 +4027,7 @@ fn validateSwitchItem(
     range_set: *RangeSet,
     item_ref: Zir.Inst.Ref,
     src_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
 ) InnerError!void {
     const item_val = (try sema.resolveSwitchItemVal(block, item_ref, src_node_offset, switch_prong_src, .none)).val;
     const maybe_prev_src = try range_set.add(item_val, item_val, switch_prong_src);
@@ -4038,10 +4037,10 @@ fn validateSwitchItem(
 fn validateSwitchItemEnum(
     sema: *Sema,
     block: *Scope.Block,
-    seen_fields: []?AstGen.SwitchProngSrc,
+    seen_fields: []?Module.SwitchProngSrc,
     item_ref: Zir.Inst.Ref,
     src_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
 ) InnerError!void {
     const mod = sema.mod;
     const item_tv = try sema.resolveSwitchItemVal(block, item_ref, src_node_offset, switch_prong_src, .none);
@@ -4073,8 +4072,8 @@ fn validateSwitchItemEnum(
 fn validateSwitchDupe(
     sema: *Sema,
     block: *Scope.Block,
-    maybe_prev_src: ?AstGen.SwitchProngSrc,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    maybe_prev_src: ?Module.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
     src_node_offset: i32,
 ) InnerError!void {
     const prev_prong_src = maybe_prev_src orelse return;
@@ -4108,7 +4107,7 @@ fn validateSwitchItemBool(
     false_count: *u8,
     item_ref: Zir.Inst.Ref,
     src_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
 ) InnerError!void {
     const item_val = (try sema.resolveSwitchItemVal(block, item_ref, src_node_offset, switch_prong_src, .none)).val;
     if (item_val.toBool()) {
@@ -4122,7 +4121,7 @@ fn validateSwitchItemBool(
     }
 }
 
-const ValueSrcMap = std.HashMap(Value, AstGen.SwitchProngSrc, Value.hash, Value.eql, std.hash_map.DefaultMaxLoadPercentage);
+const ValueSrcMap = std.HashMap(Value, Module.SwitchProngSrc, Value.hash, Value.eql, std.hash_map.DefaultMaxLoadPercentage);
 
 fn validateSwitchItemSparse(
     sema: *Sema,
@@ -4130,7 +4129,7 @@ fn validateSwitchItemSparse(
     seen_values: *ValueSrcMap,
     item_ref: Zir.Inst.Ref,
     src_node_offset: i32,
-    switch_prong_src: AstGen.SwitchProngSrc,
+    switch_prong_src: Module.SwitchProngSrc,
 ) InnerError!void {
     const item_val = (try sema.resolveSwitchItemVal(block, item_ref, src_node_offset, switch_prong_src, .none)).val;
     const entry = (try seen_values.fetchPut(item_val, switch_prong_src)) orelse return;

src/main.zig

@@ -3562,7 +3562,7 @@ pub fn cmdAstgen(
         process.exit(1);
     }
 
-    file.zir = try AstGen.generate(gpa, &file);
+    file.zir = try AstGen.generate(gpa, file.tree);
     file.zir_loaded = true;
     defer file.zir.deinit(gpa);