diff --git a/Cargo.lock b/Cargo.lock
index d63d715467c..7d451380c90 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -337,6 +337,15 @@ version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
 
+[[package]]
+name = "basic-toml"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7bfc506e7a2370ec239e1d072507b2a80c833083699d3c6fa176fbb4de8448c6"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "benchmarks-module"
 version = "0.1.0"
@@ -4258,6 +4267,7 @@ dependencies = [
  "spacetimedb-bindings-sys",
  "spacetimedb-lib",
  "spacetimedb-primitives",
+ "trybuild",
 ]
 
 [[package]]
@@ -5752,6 +5762,21 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "trybuild"
+version = "1.0.86"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8419ecd263363827c5730386f418715766f584e2f874d32c23c5b00bd9727e7e"
+dependencies = [
+ "basic-toml",
+ "glob",
+ "once_cell",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "termcolor",
+]
+
 [[package]]
 name = "tungstenite"
 version = "0.21.0"
diff --git a/Cargo.toml b/Cargo.toml
index 2de5800e6fb..5b4fc1c1374 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -240,6 +240,7 @@ tracing-core = "0.1.31"
 tracing-flame = "0.2.0"
 tracing-log = "0.1.3"
 tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }
+trybuild = "1"
 typed-arena = "2.0"
 unicode-normalization = "0.1.23"
 unicode-ident = "1.0.12"
diff --git a/crates/bindings-macro/src/lib.rs b/crates/bindings-macro/src/lib.rs
index dcab7835cac..3fc83ae5df9 100644
--- a/crates/bindings-macro/src/lib.rs
+++ b/crates/bindings-macro/src/lib.rs
@@ -17,7 +17,6 @@ use proc_macro::TokenStream as StdTokenStream;
 use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote, quote_spanned, ToTokens};
 use std::borrow::Cow;
-use std::collections::HashMap;
 use std::time::Duration;
 use syn::ext::IdentExt;
 use syn::meta::ParseNestedMeta;
@@ -330,6 +329,15 @@ fn reducer_impl(args: ReducerArgs, original_function: &ItemFn) -> syn::Result<To
         }
     };
 
+    for param in &original_function.sig.generics.params {
+        let err = |msg| syn::Error::new_spanned(param, msg);
+        match param {
+            syn::GenericParam::Lifetime(_) => {}
+            syn::GenericParam::Type(_) => return Err(err("type parameters are not allowed on reducers")),
+            syn::GenericParam::Const(_) => return Err(err("const parameters are not allowed on reducers")),
+        }
+    }
+
     let lifecycle = args.lifecycle.iter().filter_map(|lc| lc.to_lifecycle_value());
 
     // Extract all function parameters, except for `self` ones that aren't allowed.
@@ -354,6 +362,8 @@ fn reducer_impl(args: ReducerArgs, original_function: &ItemFn) -> syn::Result<To
     });
 
     let arg_tys = typed_args.iter().map(|arg| arg.ty.as_ref()).collect::<Vec<_>>();
+    let first_arg_ty = arg_tys.first().into_iter();
+    let rest_arg_tys = arg_tys.iter().skip(1);
 
     // Extract the return type.
     let ret_ty = match &original_function.sig.output {
@@ -364,13 +374,8 @@ fn reducer_impl(args: ReducerArgs, original_function: &ItemFn) -> syn::Result<To
 
     let register_describer_symbol = format!("__preinit__20_register_describer_{reducer_name}");
 
-    let generated_function = quote! {
-        fn __reducer(__ctx: spacetimedb::ReducerContext, __args: &[u8]) -> spacetimedb::ReducerResult {
-            #(spacetimedb::rt::assert_reducer_arg::<#arg_tys>();)*
-            #(spacetimedb::rt::assert_reducer_ret::<#ret_ty>();)*
-            spacetimedb::rt::invoke_reducer(#func_name, __ctx, __args)
-        }
-    };
+    let lt_params = &original_function.sig.generics;
+    let lt_where_clause = &lt_params.where_clause;
 
     let generated_describe_function = quote! {
         #[export_name = #register_describer_symbol]
@@ -385,14 +390,24 @@ fn reducer_impl(args: ReducerArgs, original_function: &ItemFn) -> syn::Result<To
         };
         #[allow(non_camel_case_types)]
         #vis struct #func_name { _never: ::core::convert::Infallible }
+        const _: () = {
+            fn _assert_args #lt_params () #lt_where_clause {
+                #(let _ = <#first_arg_ty as spacetimedb::rt::ReducerContextArg>::_ITEM;)*
+                #(let _ = <#rest_arg_tys as spacetimedb::rt::ReducerArg>::_ITEM;)*
+                #(let _ = <#ret_ty as spacetimedb::rt::IntoReducerResult>::into_result;)*
+            }
+        };
+        impl #func_name {
+            fn invoke(__ctx: spacetimedb::ReducerContext, __args: &[u8]) -> spacetimedb::ReducerResult {
+                spacetimedb::rt::invoke_reducer(#func_name, __ctx, __args)
+            }
+        }
+        #[automatically_derived]
         impl spacetimedb::rt::ReducerInfo for #func_name {
             const NAME: &'static str = #reducer_name;
             #(const LIFECYCLE: Option<spacetimedb::rt::LifecycleReducer> = Some(#lifecycle);)*
             const ARG_NAMES: &'static [Option<&'static str>] = &[#(#opt_arg_names),*];
-            const INVOKE: spacetimedb::rt::ReducerFn = {
-                #generated_function
-                __reducer
-            };
+            const INVOKE: spacetimedb::rt::ReducerFn = #func_name::invoke;
         }
     })
 }
@@ -887,6 +902,15 @@ fn table_impl(mut args: TableArgs, mut item: MutItem<syn::DeriveInput>) -> syn::
         return Err(syn::Error::new(Span::call_site(), "spacetimedb table must be a struct"));
     };
 
+    for param in &item.generics.params {
+        let err = |msg| syn::Error::new_spanned(param, msg);
+        match param {
+            syn::GenericParam::Lifetime(_) => {}
+            syn::GenericParam::Type(_) => return Err(err("type parameters are not allowed on tables")),
+            syn::GenericParam::Const(_) => return Err(err("const parameters are not allowed on tables")),
+        }
+    }
+
     let table_id_from_name_func = quote! {
         fn table_id() -> spacetimedb::TableId {
             static TABLE_ID: std::sync::OnceLock<spacetimedb::TableId> = std::sync::OnceLock::new();
@@ -1069,28 +1093,6 @@ fn table_impl(mut args: TableArgs, mut item: MutItem<syn::DeriveInput>) -> syn::
         })*
     };
 
-    // Attempt to improve the compile error when a table field doesn't satisfy
-    // the supertraits of `TableType`. We make it so the field span indicates
-    // which fields are offenders, and error reporting stops if the field doesn't
-    // implement `SpacetimeType` (which happens to be the derive macro one is
-    // supposed to use). That is, the user doesn't see errors about `Serialize`,
-    // `Deserialize` not being satisfied, which they wouldn't know what to do
-    // about.
-    let assert_fields_are_spacetimetypes = {
-        let trait_ident = Ident::new("AssertSpacetimeFields", Span::call_site());
-        let field_impls = fields
-            .iter()
-            .map(|field| (field.ty, field.span))
-            .collect::<HashMap<_, _>>()
-            .into_iter()
-            .map(|(ty, span)| quote_spanned!(span=> impl #trait_ident for #ty {}));
-
-        quote_spanned! {item.span()=>
-            trait #trait_ident: spacetimedb::SpacetimeType {}
-            #(#field_impls)*
-        }
-    };
-
     let row_type_to_table = quote!(<#row_type as spacetimedb::table::__MapRowTypeToTable>::Table);
 
     // Output all macro data
@@ -1116,7 +1118,7 @@ fn table_impl(mut args: TableArgs, mut item: MutItem<syn::DeriveInput>) -> syn::
 
     let emission = quote! {
         const _: () = {
-            #assert_fields_are_spacetimetypes
+            #(let _ = <#field_types as spacetimedb::rt::TableColumn>::_ITEM;)*
         };
 
         #trait_def
diff --git a/crates/bindings-macro/src/module.rs b/crates/bindings-macro/src/module.rs
index 4faf0793b6c..88057547595 100644
--- a/crates/bindings-macro/src/module.rs
+++ b/crates/bindings-macro/src/module.rs
@@ -32,7 +32,6 @@ pub(crate) struct SatsField<'a> {
     pub name: Option<String>,
     pub ty: &'a syn::Type,
     pub original_attrs: &'a [syn::Attribute],
-    pub span: Span,
 }
 
 pub(crate) struct SatsVariant<'a> {
@@ -57,7 +56,6 @@ pub(crate) fn sats_type_from_derive(
                 name: field.ident.as_ref().map(syn::Ident::to_string),
                 ty: &field.ty,
                 original_attrs: &field.attrs,
-                span: field.span(),
             });
             SatsTypeData::Product(fields.collect())
         }
diff --git a/crates/bindings/Cargo.toml b/crates/bindings/Cargo.toml
index 823246a3018..7d725742fc5 100644
--- a/crates/bindings/Cargo.toml
+++ b/crates/bindings/Cargo.toml
@@ -37,3 +37,4 @@ getrandom = { workspace = true, optional = true, features = ["custom"] }
 
 [dev-dependencies]
 insta.workspace = true
+trybuild.workspace = true
diff --git a/crates/bindings/src/rt.rs b/crates/bindings/src/rt.rs
index d55fe130b3c..1abac5aa3f0 100644
--- a/crates/bindings/src/rt.rs
+++ b/crates/bindings/src/rt.rs
@@ -32,6 +32,15 @@ pub fn invoke_reducer<'a, A: Args<'a>>(
     with_timestamp_set(ctx.timestamp, || reducer.invoke(&ctx, args))
 }
 /// A trait for types representing the *execution logic* of a reducer.
+#[diagnostic::on_unimplemented(
+    message = "invalid reducer signature",
+    label = "this reducer signature is not valid",
+    note = "",
+    note = "reducer signatures must match the following pattern:",
+    note = "    `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`",
+    note = "where each `Ti` type implements `SpacetimeType`.",
+    note = ""
+)]
 pub trait Reducer<'de, A: Args<'de>> {
     fn invoke(&self, ctx: &ReducerContext, args: A) -> ReducerResult;
 }
@@ -67,6 +76,10 @@ pub trait Args<'de>: Sized {
 }
 
 /// A trait of types representing the result of executing a reducer.
+#[diagnostic::on_unimplemented(
+    message = "`{Self}` is not a valid reducer return type",
+    note = "reducers cannot return values -- you can only return `()` or `Result<(), impl Display>`"
+)]
 pub trait IntoReducerResult {
     /// Convert the result into form where there is no value
     /// and the error message is a string.
@@ -85,17 +98,57 @@ impl<E: fmt::Display> IntoReducerResult for Result<(), E> {
     }
 }
 
+#[diagnostic::on_unimplemented(
+    message = "the first argument of a reducer must be `&ReducerContext`",
+    note = "all reducers must take `&ReducerContext` as their first argument"
+)]
+pub trait ReducerContextArg {
+    // a little hack used in the macro to make error messages nicer. it generates <T as ReducerContextArg>::_ITEM
+    #[doc(hidden)]
+    const _ITEM: () = ();
+}
+impl ReducerContextArg for &ReducerContext {}
+
 /// A trait of types that can be an argument of a reducer.
-pub trait ReducerArg<'de> {}
-impl<'de, T: Deserialize<'de>> ReducerArg<'de> for T {}
-impl ReducerArg<'_> for &ReducerContext {}
-/// Assert that `T: ReducerArg`.
-pub fn assert_reducer_arg<'de, T: ReducerArg<'de>>() {}
-/// Assert that `T: IntoReducerResult`.
-pub fn assert_reducer_ret<T: IntoReducerResult>() {}
+#[diagnostic::on_unimplemented(
+    message = "the reducer argument `{Self}` does not implement `SpacetimeType`",
+    note = "if you own the type, try adding `#[derive(SpacetimeType)]` to its definition"
+)]
+pub trait ReducerArg {
+    // a little hack used in the macro to make error messages nicer. it generates <T as ReducerArg>::_ITEM
+    #[doc(hidden)]
+    const _ITEM: () = ();
+}
+impl<T: SpacetimeType> ReducerArg for T {}
+
 /// Assert that a reducer type-checks with a given type.
 pub const fn assert_reducer_typecheck<'de, A: Args<'de>>(_: impl Reducer<'de, A> + Copy) {}
 
+// the macro generates <T as SpacetimeType>::make_type::<DummyTypespace>
+pub struct DummyTypespace;
+impl TypespaceBuilder for DummyTypespace {
+    fn add(
+        &mut self,
+        _: std::any::TypeId,
+        _: Option<&'static str>,
+        _: impl FnOnce(&mut Self) -> spacetimedb_lib::AlgebraicType,
+    ) -> spacetimedb_lib::AlgebraicType {
+        unreachable!()
+    }
+}
+
+#[diagnostic::on_unimplemented(
+    message = "the column type `{Self}` does not implement `SpacetimeType`",
+    note = "table column types all must implement `SpacetimeType`",
+    note = "if you own the type, try adding `#[derive(SpacetimeType)]` to its definition"
+)]
+pub trait TableColumn {
+    // a little hack used in the macro to make error messages nicer. it generates <T as TableColumn>::_ITEM
+    #[doc(hidden)]
+    const _ITEM: () = ();
+}
+impl<T: SpacetimeType> TableColumn for T {}
+
 /// Used in the last type parameter of `Reducer` to indicate that the
 /// context argument *should* be passed to the reducer logic.
 pub struct ContextArg;
diff --git a/crates/bindings/tests/ui.rs b/crates/bindings/tests/ui.rs
new file mode 100644
index 00000000000..870c2f95ec1
--- /dev/null
+++ b/crates/bindings/tests/ui.rs
@@ -0,0 +1,5 @@
+#[test]
+fn ui() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/ui/*.rs");
+}
diff --git a/crates/bindings/tests/ui/reducers.rs b/crates/bindings/tests/ui/reducers.rs
new file mode 100644
index 00000000000..e46d2887a58
--- /dev/null
+++ b/crates/bindings/tests/ui/reducers.rs
@@ -0,0 +1,28 @@
+use spacetimedb::ReducerContext;
+
+struct Test;
+
+#[spacetimedb::reducer]
+fn bad_type(_ctx: &ReducerContext, _a: Test) {}
+
+#[spacetimedb::reducer]
+fn bad_return_type(_ctx: &ReducerContext) -> Test {
+    Test
+}
+
+#[spacetimedb::reducer]
+fn lifetime<'a>(_ctx: &ReducerContext, _a: &'a str) {}
+
+#[spacetimedb::reducer]
+fn type_param<T>() {}
+
+#[spacetimedb::reducer]
+fn const_param<const X: u8>() {}
+
+#[spacetimedb::reducer]
+fn missing_ctx(_a: u8) {}
+
+#[spacetimedb::reducer]
+fn ctx_by_val(_ctx: ReducerContext, _a: u8) {}
+
+fn main() {}
diff --git a/crates/bindings/tests/ui/reducers.stderr b/crates/bindings/tests/ui/reducers.stderr
new file mode 100644
index 00000000000..4211b9237c1
--- /dev/null
+++ b/crates/bindings/tests/ui/reducers.stderr
@@ -0,0 +1,221 @@
+error: type parameters are not allowed on reducers
+  --> tests/ui/reducers.rs:17:15
+   |
+17 | fn type_param<T>() {}
+   |               ^
+
+error: const parameters are not allowed on reducers
+  --> tests/ui/reducers.rs:20:16
+   |
+20 | fn const_param<const X: u8>() {}
+   |                ^^^^^^^^^^^
+
+error[E0277]: invalid reducer signature
+ --> tests/ui/reducers.rs:6:4
+  |
+5 | #[spacetimedb::reducer]
+  | ----------------------- required by a bound introduced by this call
+6 | fn bad_type(_ctx: &ReducerContext, _a: Test) {}
+  |    ^^^^^^^^ this reducer signature is not valid
+  |
+  = help: the trait `Reducer<'_, _>` is not implemented for fn item `for<'a> fn(&'a ReducerContext, Test) {bad_type}`
+  = note:
+  = note: reducer signatures must match the following pattern:
+  = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+  = note: where each `Ti` type implements `SpacetimeType`.
+  = note:
+note: required by a bound in `register_reducer`
+ --> src/rt.rs
+  |
+  | pub fn register_reducer<'a, A: Args<'a>, I: ReducerInfo>(_: impl Reducer<'a, A>) {
+  |                                                                  ^^^^^^^^^^^^^^ required by this bound in `register_reducer`
+
+error[E0277]: the reducer argument `Test` does not implement `SpacetimeType`
+ --> tests/ui/reducers.rs:6:40
+  |
+6 | fn bad_type(_ctx: &ReducerContext, _a: Test) {}
+  |                                        ^^^^ the trait `SpacetimeType` is not implemented for `Test`, which is required by `Test: ReducerArg`
+  |
+  = note: if you own the type, try adding `#[derive(SpacetimeType)]` to its definition
+  = note: required for `Test` to implement `ReducerArg`
+
+error[E0277]: invalid reducer signature
+ --> tests/ui/reducers.rs:6:4
+  |
+5 | #[spacetimedb::reducer]
+  | ----------------------- required by a bound introduced by this call
+6 | fn bad_type(_ctx: &ReducerContext, _a: Test) {}
+  |    ^^^^^^^^ this reducer signature is not valid
+  |
+  = help: the trait `Reducer<'_, _>` is not implemented for fn item `for<'a> fn(&'a ReducerContext, Test) {bad_type}`
+  = note:
+  = note: reducer signatures must match the following pattern:
+  = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+  = note: where each `Ti` type implements `SpacetimeType`.
+  = note:
+note: required by a bound in `invoke_reducer`
+ --> src/rt.rs
+  |
+  | pub fn invoke_reducer<'a, A: Args<'a>>(
+  |        -------------- required by a bound in this function
+  |     reducer: impl Reducer<'a, A>,
+  |                   ^^^^^^^^^^^^^^ required by this bound in `invoke_reducer`
+
+error[E0277]: invalid reducer signature
+ --> tests/ui/reducers.rs:9:4
+  |
+8 | #[spacetimedb::reducer]
+  | ----------------------- required by a bound introduced by this call
+9 | fn bad_return_type(_ctx: &ReducerContext) -> Test {
+  |    ^^^^^^^^^^^^^^^ this reducer signature is not valid
+  |
+  = help: the trait `Reducer<'_, _>` is not implemented for fn item `for<'a> fn(&'a ReducerContext) -> Test {bad_return_type}`
+  = note:
+  = note: reducer signatures must match the following pattern:
+  = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+  = note: where each `Ti` type implements `SpacetimeType`.
+  = note:
+note: required by a bound in `register_reducer`
+ --> src/rt.rs
+  |
+  | pub fn register_reducer<'a, A: Args<'a>, I: ReducerInfo>(_: impl Reducer<'a, A>) {
+  |                                                                  ^^^^^^^^^^^^^^ required by this bound in `register_reducer`
+
+error[E0277]: `Test` is not a valid reducer return type
+ --> tests/ui/reducers.rs:9:46
+  |
+9 | fn bad_return_type(_ctx: &ReducerContext) -> Test {
+  |                                              ^^^^ the trait `IntoReducerResult` is not implemented for `Test`
+  |
+  = note: reducers cannot return values -- you can only return `()` or `Result<(), impl Display>`
+  = help: the following other types implement trait `IntoReducerResult`:
+            Result<(), E>
+            ()
+
+error[E0277]: invalid reducer signature
+ --> tests/ui/reducers.rs:9:4
+  |
+8 | #[spacetimedb::reducer]
+  | ----------------------- required by a bound introduced by this call
+9 | fn bad_return_type(_ctx: &ReducerContext) -> Test {
+  |    ^^^^^^^^^^^^^^^ this reducer signature is not valid
+  |
+  = help: the trait `Reducer<'_, _>` is not implemented for fn item `for<'a> fn(&'a ReducerContext) -> Test {bad_return_type}`
+  = note:
+  = note: reducer signatures must match the following pattern:
+  = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+  = note: where each `Ti` type implements `SpacetimeType`.
+  = note:
+note: required by a bound in `invoke_reducer`
+ --> src/rt.rs
+  |
+  | pub fn invoke_reducer<'a, A: Args<'a>>(
+  |        -------------- required by a bound in this function
+  |     reducer: impl Reducer<'a, A>,
+  |                   ^^^^^^^^^^^^^^ required by this bound in `invoke_reducer`
+
+error[E0277]: invalid reducer signature
+  --> tests/ui/reducers.rs:23:4
+   |
+22 | #[spacetimedb::reducer]
+   | ----------------------- required by a bound introduced by this call
+23 | fn missing_ctx(_a: u8) {}
+   |    ^^^^^^^^^^^ this reducer signature is not valid
+   |
+   = help: the trait `Reducer<'_, _>` is not implemented for fn item `fn(u8) {missing_ctx}`
+   = note:
+   = note: reducer signatures must match the following pattern:
+   = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+   = note: where each `Ti` type implements `SpacetimeType`.
+   = note:
+note: required by a bound in `register_reducer`
+  --> src/rt.rs
+   |
+   | pub fn register_reducer<'a, A: Args<'a>, I: ReducerInfo>(_: impl Reducer<'a, A>) {
+   |                                                                  ^^^^^^^^^^^^^^ required by this bound in `register_reducer`
+
+error[E0277]: the first argument of a reducer must be `&ReducerContext`
+  --> tests/ui/reducers.rs:23:20
+   |
+23 | fn missing_ctx(_a: u8) {}
+   |                    ^^ the trait `ReducerContextArg` is not implemented for `u8`
+   |
+   = note: all reducers must take `&ReducerContext` as their first argument
+   = help: the trait `ReducerContextArg` is implemented for `&ReducerContext`
+
+error[E0277]: invalid reducer signature
+  --> tests/ui/reducers.rs:23:4
+   |
+22 | #[spacetimedb::reducer]
+   | ----------------------- required by a bound introduced by this call
+23 | fn missing_ctx(_a: u8) {}
+   |    ^^^^^^^^^^^ this reducer signature is not valid
+   |
+   = help: the trait `Reducer<'_, _>` is not implemented for fn item `fn(u8) {missing_ctx}`
+   = note:
+   = note: reducer signatures must match the following pattern:
+   = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+   = note: where each `Ti` type implements `SpacetimeType`.
+   = note:
+note: required by a bound in `invoke_reducer`
+  --> src/rt.rs
+   |
+   | pub fn invoke_reducer<'a, A: Args<'a>>(
+   |        -------------- required by a bound in this function
+   |     reducer: impl Reducer<'a, A>,
+   |                   ^^^^^^^^^^^^^^ required by this bound in `invoke_reducer`
+
+error[E0277]: invalid reducer signature
+  --> tests/ui/reducers.rs:26:4
+   |
+25 | #[spacetimedb::reducer]
+   | ----------------------- required by a bound introduced by this call
+26 | fn ctx_by_val(_ctx: ReducerContext, _a: u8) {}
+   |    ^^^^^^^^^^ this reducer signature is not valid
+   |
+   = help: the trait `Reducer<'_, _>` is not implemented for fn item `fn(ReducerContext, u8) {ctx_by_val}`
+   = note:
+   = note: reducer signatures must match the following pattern:
+   = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+   = note: where each `Ti` type implements `SpacetimeType`.
+   = note:
+note: required by a bound in `register_reducer`
+  --> src/rt.rs
+   |
+   | pub fn register_reducer<'a, A: Args<'a>, I: ReducerInfo>(_: impl Reducer<'a, A>) {
+   |                                                                  ^^^^^^^^^^^^^^ required by this bound in `register_reducer`
+
+error[E0277]: the first argument of a reducer must be `&ReducerContext`
+  --> tests/ui/reducers.rs:26:21
+   |
+26 | fn ctx_by_val(_ctx: ReducerContext, _a: u8) {}
+   |                     ^^^^^^^^^^^^^^
+   |                     |
+   |                     the trait `ReducerContextArg` is not implemented for `ReducerContext`
+   |                     the trait `ReducerContextArg` is not implemented for `ReducerContext`
+   |
+   = note: the trait bound `ReducerContext: ReducerContextArg` is not satisfied
+   = note: all reducers must take `&ReducerContext` as their first argument
+   = help: the trait `ReducerContextArg` is implemented for `&ReducerContext`
+
+error[E0277]: invalid reducer signature
+  --> tests/ui/reducers.rs:26:4
+   |
+25 | #[spacetimedb::reducer]
+   | ----------------------- required by a bound introduced by this call
+26 | fn ctx_by_val(_ctx: ReducerContext, _a: u8) {}
+   |    ^^^^^^^^^^ this reducer signature is not valid
+   |
+   = help: the trait `Reducer<'_, _>` is not implemented for fn item `fn(ReducerContext, u8) {ctx_by_val}`
+   = note:
+   = note: reducer signatures must match the following pattern:
+   = note:     `Fn(&ReducerContext, [T1, ...]) [-> Result<(), impl Display>]`
+   = note: where each `Ti` type implements `SpacetimeType`.
+   = note:
+note: required by a bound in `invoke_reducer`
+  --> src/rt.rs
+   |
+   | pub fn invoke_reducer<'a, A: Args<'a>>(
+   |        -------------- required by a bound in this function
+   |     reducer: impl Reducer<'a, A>,
+   |                   ^^^^^^^^^^^^^^ required by this bound in `invoke_reducer`
diff --git a/crates/bindings/tests/ui/tables.rs b/crates/bindings/tests/ui/tables.rs
new file mode 100644
index 00000000000..c698f74ce3d
--- /dev/null
+++ b/crates/bindings/tests/ui/tables.rs
@@ -0,0 +1,16 @@
+struct Test;
+
+#[spacetimedb::table(name = table)]
+struct Table {
+    x: Test,
+}
+
+#[spacetimedb::table(name = type_param)]
+struct TypeParam<T> {
+    t: T,
+}
+
+#[spacetimedb::table(name = const_param)]
+struct ConstParam<const X: u8> {}
+
+fn main() {}
diff --git a/crates/bindings/tests/ui/tables.stderr b/crates/bindings/tests/ui/tables.stderr
new file mode 100644
index 00000000000..0c4876c2306
--- /dev/null
+++ b/crates/bindings/tests/ui/tables.stderr
@@ -0,0 +1,108 @@
+error: type parameters are not allowed on tables
+ --> tests/ui/tables.rs:9:18
+  |
+9 | struct TypeParam<T> {
+  |                  ^
+
+error: const parameters are not allowed on tables
+  --> tests/ui/tables.rs:14:19
+   |
+14 | struct ConstParam<const X: u8> {}
+   |                   ^^^^^^^^^^^
+
+error[E0277]: the column type `Test` does not implement `SpacetimeType`
+ --> tests/ui/tables.rs:5:8
+  |
+5 |     x: Test,
+  |        ^^^^ the trait `SpacetimeType` is not implemented for `Test`, which is required by `Test: TableColumn`
+  |
+  = note: table column types all must implement `SpacetimeType`
+  = note: if you own the type, try adding `#[derive(SpacetimeType)]` to its definition
+  = note: required for `Test` to implement `TableColumn`
+
+error[E0277]: the trait bound `Test: SpacetimeType` is not satisfied
+ --> tests/ui/tables.rs:5:8
+  |
+5 |     x: Test,
+  |        ^^^^ the trait `SpacetimeType` is not implemented for `Test`
+  |
+  = note: if you own the type, try adding `#[derive(SpacetimeType)]` to its definition
+  = help: the following other types implement trait `SpacetimeType`:
+            bool
+            i8
+            i16
+            i32
+            i64
+            i128
+            u8
+            u16
+          and $N others
+
+error[E0277]: the trait bound `Test: Deserialize<'de>` is not satisfied
+ --> tests/ui/tables.rs:5:8
+  |
+3 | #[spacetimedb::table(name = table)]
+  | ----------------------------------- required by a bound introduced by this call
+4 | struct Table {
+5 |     x: Test,
+  |        ^^^^ the trait `Deserialize<'de>` is not implemented for `Test`
+  |
+  = help: the following other types implement trait `Deserialize<'de>`:
+            bool
+            i8
+            i16
+            i32
+            i64
+            i128
+            u8
+            u16
+          and $N others
+note: required by a bound in `spacetimedb::spacetimedb_lib::de::SeqProductAccess::next_element`
+ --> $WORKSPACE/crates/sats/src/de.rs
+  |
+  |     fn next_element<T: Deserialize<'de>>(&mut self) -> Result<Option<T>, Self::Error> {
+  |                        ^^^^^^^^^^^^^^^^ required by this bound in `SeqProductAccess::next_element`
+
+error[E0277]: the trait bound `Test: Deserialize<'_>` is not satisfied
+ --> tests/ui/tables.rs:5:8
+  |
+5 |     x: Test,
+  |        ^^^^ the trait `Deserialize<'_>` is not implemented for `Test`
+  |
+  = help: the following other types implement trait `Deserialize<'de>`:
+            bool
+            i8
+            i16
+            i32
+            i64
+            i128
+            u8
+            u16
+          and $N others
+note: required by a bound in `get_field_value`
+ --> $WORKSPACE/crates/sats/src/de.rs
+  |
+  |     fn get_field_value<T: Deserialize<'de>>(&mut self) -> Result<T, Self::Error> {
+  |                           ^^^^^^^^^^^^^^^^ required by this bound in `NamedProductAccess::get_field_value`
+
+error[E0277]: the trait bound `Test: Serialize` is not satisfied
+ --> tests/ui/tables.rs:5:8
+  |
+5 |     x: Test,
+  |        ^^^^ the trait `Serialize` is not implemented for `Test`
+  |
+  = help: the following other types implement trait `Serialize`:
+            bool
+            i8
+            i16
+            i32
+            i64
+            i128
+            u8
+            u16
+          and $N others
+note: required by a bound in `spacetimedb::spacetimedb_lib::ser::SerializeNamedProduct::serialize_element`
+ --> $WORKSPACE/crates/sats/src/ser.rs
+  |
+  |     fn serialize_element<T: Serialize + ?Sized>(&mut self, name: Option<&str>, elem: &T) -> Result<(), Self::Error>;
+  |                             ^^^^^^^^^ required by this bound in `SerializeNamedProduct::serialize_element`
diff --git a/crates/sats/src/typespace.rs b/crates/sats/src/typespace.rs
index 6579643c7be..b0a8f03bf05 100644
--- a/crates/sats/src/typespace.rs
+++ b/crates/sats/src/typespace.rs
@@ -231,6 +231,9 @@ pub trait GroundSpacetimeType {
 
 /// A trait for Rust types that can be represented as an [`AlgebraicType`]
 /// provided a typing context `typespace`.
+// TODO: we might want to have a note about what to do if you're trying to use a type from another crate in your table.
+// keep this note in sync with the ones on spacetimedb::rt::{ReducerArg, TableColumn}
+#[diagnostic::on_unimplemented(note = "if you own the type, try adding `#[derive(SpacetimeType)]` to its definition")]
 pub trait SpacetimeType {
     /// Returns an `AlgebraicType` representing the type for `Self` in SATS
     /// and in the typing context in `typespace`.
@@ -327,6 +330,7 @@ impl_primitives! {
 impl_st!([](), AlgebraicType::unit());
 impl_st!([] str, AlgebraicType::String);
 impl_st!([T] [T], ts => AlgebraicType::array(T::make_type(ts)));
+impl_st!([T: ?Sized] &T, ts => T::make_type(ts));
 impl_st!([T: ?Sized] Box<T>, ts => T::make_type(ts));
 impl_st!([T: ?Sized] Rc<T>, ts => T::make_type(ts));
 impl_st!([T: ?Sized] Arc<T>, ts => T::make_type(ts));