add the fasFn helper

3 files changed, 27 insertions, 11 deletions

diff --git a/helpers.zig b/helpers.zig
index 1a56231..7bb695e 100644
--- a/helpers.zig
+++ b/helpers.zig
@@ -86,3 +86,19 @@ fn sliceFromValue(sqlite_value: *c.sqlite3_value) []const u8 {
 
     return value[0..size];
 }
+
+// Returns true if the type T has a function named `name`.
+pub fn hasFn(comptime T: type, comptime name: []const u8) bool {
+    if (!@hasDecl(T, name)) {
+        return false;
+    }
+
+    const decl = @field(T, name);
+    const decl_type = @TypeOf(decl);
+    const decl_type_info = @typeInfo(decl_type);
+
+    return switch (decl_type_info) {
+        .Fn => true,
+        else => false,
+    };
+}
diff --git a/sqlite.zig b/sqlite.zig
index c3ecb84..3759884 100644
--- a/sqlite.zig
+++ b/sqlite.zig
@@ -1693,7 +1693,7 @@ pub const DynamicStatement = struct {
                         try self.bindField(info.backing_integer.?, options, field_name, i, @as(info.backing_integer.?, @bitCast(field)));
                         return;
                     }
-                    if (!comptime std.meta.trait.hasFn("bindField")(FieldType)) {
+                    if (!comptime helpers.hasFn(FieldType, "bindField")) {
                         @compileError("cannot bind field " ++ field_name ++ " of type " ++ @typeName(FieldType) ++ ", consider implementing the bindField() method");
                     }
 
diff --git a/vtab.zig b/vtab.zig
index 7c2dafe..eb73990 100644
--- a/vtab.zig
+++ b/vtab.zig
@@ -318,7 +318,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.init function must have the signature `fn init(allocator: std.mem.Allocator, parent: *Table) InitError!*Cursor`
         ;
 
-        if (!meta.trait.hasFn("init")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "init")) {
             @compileError("the Cursor type must have an init function, " ++ error_message);
         }
 
@@ -336,7 +336,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.deinit function must have the signature `fn deinit(cursor: *Cursor) void`
         ;
 
-        if (!meta.trait.hasFn("deinit")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "deinit")) {
             @compileError("the Cursor type must have a deinit function, " ++ error_message);
         }
 
@@ -357,7 +357,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.next function must have the signature `fn next(cursor: *Cursor, diags: *sqlite.vtab.VTabDiagnostics) NextError!void`
         ;
 
-        if (!meta.trait.hasFn("next")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "next")) {
             @compileError("the Cursor type must have a next function, " ++ error_message);
         }
 
@@ -379,7 +379,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.hasNext function must have the signature `fn hasNext(cursor: *Cursor, diags: *sqlite.vtab.VTabDiagnostics) HasNextError!bool`
         ;
 
-        if (!meta.trait.hasFn("hasNext")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "hasNext")) {
             @compileError("the Cursor type must have a hasNext function, " ++ error_message);
         }
 
@@ -401,7 +401,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.filter function must have the signature `fn filter(cursor: *Cursor, diags: *sqlite.vtab.VTabDiagnostics, index: sqlite.vtab.IndexIdentifier, args: []FilterArg) FilterError!bool`
         ;
 
-        if (!meta.trait.hasFn("filter")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "filter")) {
             @compileError("the Cursor type must have a filter function, " ++ error_message);
         }
 
@@ -428,7 +428,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.column function must have the signature `fn column(cursor: *Cursor, diags: *sqlite.vtab.VTabDiagnostics, column_number: i32) ColumnError!Column`
         ;
 
-        if (!meta.trait.hasFn("column")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "column")) {
             @compileError("the Cursor type must have a column function, " ++ error_message);
         }
 
@@ -451,7 +451,7 @@ fn validateCursorType(comptime Table: type) void {
             \\the Cursor.rowId function must have the signature `fn rowId(cursor: *Cursor, diags: *sqlite.vtab.VTabDiagnostics) RowIDError!i64`
         ;
 
-        if (!meta.trait.hasFn("rowId")(Cursor)) {
+        if (!comptime helpers.hasFn(Cursor, "rowId")) {
             @compileError("the Cursor type must have a rowId function, " ++ error_message);
         }
 
@@ -476,7 +476,7 @@ fn validateTableType(comptime Table: type) void {
             \\the Table.init function must have the signature `fn init(allocator: std.mem.Allocator, diags: *sqlite.vtab.VTabDiagnostics, args: []const ModuleArgument) InitError!*Table`
         ;
 
-        if (!meta.trait.hasFn("init")(Table)) {
+        if (!comptime helpers.hasFn(Table, "init")) {
             @compileError("the Table type must have a init function, " ++ error_message);
         }
 
@@ -496,7 +496,7 @@ fn validateTableType(comptime Table: type) void {
             \\the Table.deinit function must have the signature `fn deinit(table: *Table, allocator: std.mem.Allocator) void`
         ;
 
-        if (!meta.trait.hasFn("deinit")(Table)) {
+        if (!comptime helpers.hasFn(Table, "deinit")) {
             @compileError("the Table type must have a deinit function, " ++ error_message);
         }
 
@@ -518,7 +518,7 @@ fn validateTableType(comptime Table: type) void {
             \\the Table.buildBestIndex function must have the signature `fn buildBestIndex(table: *Table, diags: *sqlite.vtab.VTabDiagnostics, builder: *sqlite.vtab.BestIndexBuilder) BuildBestIndexError!void`
         ;
 
-        if (!meta.trait.hasFn("buildBestIndex")(Table)) {
+        if (!comptime helpers.hasFn(Table, "buildBestIndex")) {
             @compileError("the Table type must have a buildBestIndex function, " ++ error_message);
         }