reflect: remove comptime var pointer returns

Following ziglang/zig#19414 and
https://ziggit.dev/t/comptime-mutable-memory-changes/3702 change in zig,
we cannot return `comptime var` pointer anymore.

Author: krichprollsch

src/block.zig

@@ -99,7 +99,7 @@ const Pull = struct {
 ///       (See https://github.com/ziglang/zig/issues/8289)
 pub fn block(
     comptime T: type,
-    items: []T,
+    comptime items: []const T,
     context: anytype,
     comptime lessThan: fn (@TypeOf(context), lhs: T, rhs: T) bool,
 ) void {

src/generate.zig

@@ -24,11 +24,12 @@ const loadFn = @import("private_api.zig").loadFn;
 // reflect the user-defined types to obtain type information (T_refl)
 // This function must be called at comptime by the root file of the project
 // and stored in a constant named `Types`
-pub fn reflect(comptime types: anytype) []refl.Struct {
+pub fn reflect(comptime types: anytype) []const refl.Struct {
     std.debug.assert(@inComptime());
 
     // call types reflection
-    return refl.do(types) catch unreachable;
+    @compileLog(refl.do(types));
+    return refl.do(types) catch |e| @compileError(e);
 }
 
 // Import user-defined types

src/reflect.zig

@@ -241,7 +241,7 @@ pub const Type = struct {
     }
 
     // check that user-defined types have been provided as an API
-    pub fn lookup(comptime self: *Type, comptime structs: []Struct) Error!void {
+    pub fn lookup(comptime self: *Type, comptime structs: []const Struct) Error!void {
         std.debug.assert(@inComptime());
 
         // lookup unecessary
@@ -462,7 +462,7 @@ pub const Func = struct {
 
     setter_index: ?u8, // TODO: not ideal, is there a cleaner solution?
 
-    fn lookupTypes(comptime self: *Func, comptime structs: []Struct) Error!void {
+    fn lookupTypes(comptime self: *const Func, comptime structs: []const Struct) Error!void {
         inline for (self.args) |*arg| {
             try arg.lookup(structs);
         }
@@ -738,12 +738,12 @@ pub const Struct = struct {
     has_constructor: bool,
     constructor: Func,
 
-    getters: []Func,
-    setters: []Func,
-    methods: []Func,
+    getters: []const Func,
+    setters: []const Func,
+    methods: []const Func,
 
     // nested types
-    nested: []StructNested,
+    nested: []const StructNested,
 
     pub fn Self(comptime self: Struct) type {
         comptime {
@@ -784,7 +784,7 @@ pub const Struct = struct {
         return @sizeOf(self.Self()) == 0;
     }
 
-    fn lookupTypes(comptime self: *Struct, comptime structs: []Struct) Error!void {
+    fn lookupTypes(comptime self: *Struct, comptime structs: []const Struct) Error!void {
         try self.value.lookup(structs);
         if (self.has_constructor) {
             try self.constructor.lookupTypes(structs);
@@ -1323,6 +1323,11 @@ pub const Struct = struct {
             }
         }
 
+        const final_getters = getters;
+        const final_setters = setters;
+        const final_methods = methods;
+        const final_nested = nested;
+
         return Struct{
             // struct info
             .name = struct_name,
@@ -1343,12 +1348,12 @@ pub const Struct = struct {
             // struct functions
             .has_constructor = has_constructor,
             .constructor = constructor,
-            .getters = getters[0..],
-            .setters = setters[0..],
-            .methods = methods[0..],
+            .getters = &final_getters,
+            .setters = &final_setters,
+            .methods = &final_methods,
 
             // nested types
-            .nested = nested[0..],
+            .nested = &final_nested,
         };
     }
 };
@@ -1432,7 +1437,7 @@ fn lookupException(comptime all: []Struct) Error!void {
     }
 }
 
-pub fn do(comptime types: anytype) Error![]Struct {
+pub fn do(comptime types: anytype) Error![]const Struct {
     comptime {
 
         // check types provided
@@ -1475,7 +1480,8 @@ pub fn do(comptime types: anytype) Error![]Struct {
             try s.lookupTypes(&all);
         }
 
-        return &all;
+        const final = all;
+        return &final;
     }
 }