stage2: move enum types into the InternPool

Unlike unions and structs, enums are actually *encoded* into the
InternPool directly, rather than using the SegmentedList trick. This
results in them being quite compact, and greatly improved the ergonomics
of using enum types throughout the compiler.

It did however require introducing a new concept to the InternPool which
is an "incomplete" item - something that is added to gain a permanent
Index, but which is then mutated in place. This was necessary because
enum tag values and tag types may reference the namespaces created by
the enum itself, which required constructing the namespace, decl, and
calling analyzeDecl on the decl, which required the decl value, which
required the enum type, which required an InternPool index to be
assigned and for it to be meaningful.

The API for updating enums in place turned out to be quite slick and
efficient - the methods directly populate pre-allocated arrays and
return the information necessary to output the same compilation errors
as before.

1 files changed, 28 insertions, 167 deletions

diff --git a/src/Module.zig b/src/Module.zig
index 6478f7ce4f..6bcd148e67 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -886,29 +886,17 @@ pub const Decl = struct {
     /// Only returns it if the Decl is the owner.
     pub fn getInnerNamespaceIndex(decl: *Decl, mod: *Module) Namespace.OptionalIndex {
         if (!decl.owns_tv) return .none;
-        switch (decl.val.ip_index) {
-            .empty_struct_type => return .none,
-            .none => {
-                const ty = (decl.val.castTag(.ty) orelse return .none).data;
-                switch (ty.tag()) {
-                    .enum_full, .enum_nonexhaustive => {
-                        const enum_obj = ty.cast(Type.Payload.EnumFull).?.data;
-                        return enum_obj.namespace.toOptional();
-                    },
-
-                    else => return .none,
-                }
-            },
-            else => return switch (mod.intern_pool.indexToKey(decl.val.ip_index)) {
+        return switch (decl.val.ip_index) {
+            .empty_struct_type => .none,
+            .none => .none,
+            else => switch (mod.intern_pool.indexToKey(decl.val.ip_index)) {
                 .opaque_type => |opaque_type| opaque_type.namespace.toOptional(),
                 .struct_type => |struct_type| struct_type.namespace,
-                .union_type => |union_type| {
-                    const union_obj = mod.unionPtr(union_type.index);
-                    return union_obj.namespace.toOptional();
-                },
+                .union_type => |union_type| mod.unionPtr(union_type.index).namespace.toOptional(),
+                .enum_type => |enum_type| enum_type.namespace,
                 else => .none,
             },
-        }
+        };
     }
 
     /// Same as `getInnerNamespaceIndex` but additionally obtains the pointer.
@@ -1135,28 +1123,6 @@ pub const Struct = struct {
         return mod.declPtr(s.owner_decl).srcLoc(mod);
     }
 
-    pub fn fieldSrcLoc(s: Struct, mod: *Module, query: FieldSrcQuery) SrcLoc {
-        @setCold(true);
-        const owner_decl = mod.declPtr(s.owner_decl);
-        const file = owner_decl.getFileScope(mod);
-        const tree = file.getTree(mod.gpa) catch |err| {
-            // In this case we emit a warning + a less precise source location.
-            log.warn("unable to load {s}: {s}", .{
-                file.sub_file_path, @errorName(err),
-            });
-            return s.srcLoc(mod);
-        };
-        const node = owner_decl.relativeToNodeIndex(0);
-
-        var buf: [2]Ast.Node.Index = undefined;
-        if (tree.fullContainerDecl(&buf, node)) |container_decl| {
-            return queryFieldSrc(tree.*, query, file, container_decl);
-        } else {
-            // This struct was generated using @Type
-            return s.srcLoc(mod);
-        }
-    }
-
     pub fn haveFieldTypes(s: Struct) bool {
         return switch (s.status) {
             .none,
@@ -1237,110 +1203,6 @@ pub const Struct = struct {
     }
 };
 
-/// Represents the data that an enum declaration provides, when the fields
-/// are auto-numbered, and there are no declarations. The integer tag type
-/// is inferred to be the smallest power of two unsigned int that fits
-/// the number of fields.
-pub const EnumSimple = struct {
-    /// The Decl that corresponds to the enum itself.
-    owner_decl: Decl.Index,
-    /// Set of field names in declaration order.
-    fields: NameMap,
-
-    pub const NameMap = EnumFull.NameMap;
-
-    pub fn srcLoc(self: EnumSimple, mod: *Module) SrcLoc {
-        const owner_decl = mod.declPtr(self.owner_decl);
-        return .{
-            .file_scope = owner_decl.getFileScope(mod),
-            .parent_decl_node = owner_decl.src_node,
-            .lazy = LazySrcLoc.nodeOffset(0),
-        };
-    }
-};
-
-/// Represents the data that an enum declaration provides, when there are no
-/// declarations. However an integer tag type is provided, and the enum tag values
-/// are explicitly provided.
-pub const EnumNumbered = struct {
-    /// The Decl that corresponds to the enum itself.
-    owner_decl: Decl.Index,
-    /// An integer type which is used for the numerical value of the enum.
-    /// Whether zig chooses this type or the user specifies it, it is stored here.
-    tag_ty: Type,
-    /// Set of field names in declaration order.
-    fields: NameMap,
-    /// Maps integer tag value to field index.
-    /// Entries are in declaration order, same as `fields`.
-    /// If this hash map is empty, it means the enum tags are auto-numbered.
-    values: ValueMap,
-
-    pub const NameMap = EnumFull.NameMap;
-    pub const ValueMap = EnumFull.ValueMap;
-
-    pub fn srcLoc(self: EnumNumbered, mod: *Module) SrcLoc {
-        const owner_decl = mod.declPtr(self.owner_decl);
-        return .{
-            .file_scope = owner_decl.getFileScope(mod),
-            .parent_decl_node = owner_decl.src_node,
-            .lazy = LazySrcLoc.nodeOffset(0),
-        };
-    }
-};
-
-/// Represents the data that an enum declaration provides, when there is
-/// at least one tag value explicitly specified, or at least one declaration.
-pub const EnumFull = struct {
-    /// The Decl that corresponds to the enum itself.
-    owner_decl: Decl.Index,
-    /// An integer type which is used for the numerical value of the enum.
-    /// Whether zig chooses this type or the user specifies it, it is stored here.
-    tag_ty: Type,
-    /// Set of field names in declaration order.
-    fields: NameMap,
-    /// Maps integer tag value to field index.
-    /// Entries are in declaration order, same as `fields`.
-    /// If this hash map is empty, it means the enum tags are auto-numbered.
-    values: ValueMap,
-    /// Represents the declarations inside this enum.
-    namespace: Namespace.Index,
-    /// true if zig inferred this tag type, false if user specified it
-    tag_ty_inferred: bool,
-
-    pub const NameMap = std.StringArrayHashMapUnmanaged(void);
-    pub const ValueMap = std.ArrayHashMapUnmanaged(Value, void, Value.ArrayHashContext, false);
-
-    pub fn srcLoc(self: EnumFull, mod: *Module) SrcLoc {
-        const owner_decl = mod.declPtr(self.owner_decl);
-        return .{
-            .file_scope = owner_decl.getFileScope(mod),
-            .parent_decl_node = owner_decl.src_node,
-            .lazy = LazySrcLoc.nodeOffset(0),
-        };
-    }
-
-    pub fn fieldSrcLoc(e: EnumFull, mod: *Module, query: FieldSrcQuery) SrcLoc {
-        @setCold(true);
-        const owner_decl = mod.declPtr(e.owner_decl);
-        const file = owner_decl.getFileScope(mod);
-        const tree = file.getTree(mod.gpa) catch |err| {
-            // In this case we emit a warning + a less precise source location.
-            log.warn("unable to load {s}: {s}", .{
-                file.sub_file_path, @errorName(err),
-            });
-            return e.srcLoc(mod);
-        };
-        const node = owner_decl.relativeToNodeIndex(0);
-        var buf: [2]Ast.Node.Index = undefined;
-        if (tree.fullContainerDecl(&buf, node)) |container_decl| {
-            return queryFieldSrc(tree.*, query, file, container_decl);
-        } else {
-            // This enum was generated using @Type
-            return e.srcLoc(mod);
-        }
-    }
-};
-
 pub const Union = struct {
     /// An enum type which is used for the tag of the union.
     /// This type is created even for untagged unions, even when the memory
@@ -1427,28 +1289,6 @@ pub const Union = struct {
         };
     }
 
-    pub fn fieldSrcLoc(u: Union, mod: *Module, query: FieldSrcQuery) SrcLoc {
-        @setCold(true);
-        const owner_decl = mod.declPtr(u.owner_decl);
-        const file = owner_decl.getFileScope(mod);
-        const tree = file.getTree(mod.gpa) catch |err| {
-            // In this case we emit a warning + a less precise source location.
-            log.warn("unable to load {s}: {s}", .{
-                file.sub_file_path, @errorName(err),
-            });
-            return u.srcLoc(mod);
-        };
-        const node = owner_decl.relativeToNodeIndex(0);
-
-        var buf: [2]Ast.Node.Index = undefined;
-        if (tree.fullContainerDecl(&buf, node)) |container_decl| {
-            return queryFieldSrc(tree.*, query, file, container_decl);
-        } else {
-            // This union was generated using @Type
-            return u.srcLoc(mod);
-        }
-    }
-
     pub fn haveFieldTypes(u: Union) bool {
         return switch (u.status) {
             .none,
@@ -7313,3 +7153,24 @@ pub fn typeToUnion(mod: *Module, ty: Type) ?*Union {
     const union_index = mod.intern_pool.indexToUnion(ty.ip_index).unwrap() orelse return null;
     return mod.unionPtr(union_index);
 }
+
+pub fn fieldSrcLoc(mod: *Module, owner_decl_index: Decl.Index, query: FieldSrcQuery) SrcLoc {
+    @setCold(true);
+    const owner_decl = mod.declPtr(owner_decl_index);
+    const file = owner_decl.getFileScope(mod);
+    const tree = file.getTree(mod.gpa) catch |err| {
+        // In this case we emit a warning + a less precise source location.
+        log.warn("unable to load {s}: {s}", .{
+            file.sub_file_path, @errorName(err),
+        });
+        return owner_decl.srcLoc(mod);
+    };
+    const node = owner_decl.relativeToNodeIndex(0);
+    var buf: [2]Ast.Node.Index = undefined;
+    if (tree.fullContainerDecl(&buf, node)) |container_decl| {
+        return queryFieldSrc(tree.*, query, file, container_decl);
+    } else {
+        // This type was generated using @Type
+        return owner_decl.srcLoc(mod);
+    }
+}