add better default behavior on fill struct fields diagnostic

Signed-off-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

crates/syntax/src/ast/make.rs

@@ -59,8 +59,27 @@ pub mod ext {
     pub fn expr_todo() -> ast::Expr {
         expr_from_text("todo!()")
     }
-    pub fn expr_default() -> ast::Expr {
-        expr_from_text("Default::default()")
+    pub fn expr_ty_default(ty: &ast::Type) -> ast::Expr {
+        expr_from_text(&format!("{}::default()", ty))
+    }
+    pub fn expr_ty_new(ty: &ast::Type) -> ast::Expr {
+        expr_from_text(&format!("{}::new()", ty))
+    }
+
+    pub fn zero_number() -> ast::Expr {
+        expr_from_text("0")
+    }
+    pub fn zero_float() -> ast::Expr {
+        expr_from_text("0.0")
+    }
+    pub fn empty_str() -> ast::Expr {
+        expr_from_text(r#""""#)
+    }
+    pub fn empty_char() -> ast::Expr {
+        expr_from_text("''")
+    }
+    pub fn default_bool() -> ast::Expr {
+        expr_from_text("false")
     }
     pub fn empty_block_expr() -> ast::BlockExpr {
         block_expr(None, None)