Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/misc/rust/src/lib.rs

@@ -0,0 +1,47 @@
+pub use wasmtime_rust_macro::wasmtime;
+
+// modules used by the macro
+#[doc(hidden)]
+pub mod __rt {
+    pub use anyhow;
+    pub use cranelift_codegen;
+    pub use cranelift_native;
+    pub use wasmtime_interface_types;
+    pub use wasmtime_jit;
+
+    use std::convert::{TryFrom, TryInto};
+    use wasmtime_interface_types::Value;
+
+    pub trait FromVecValue: Sized {
+        fn from(list: Vec<Value>) -> anyhow::Result<Self>;
+    }
+
+    macro_rules! tuple {
+        ($(($($a:ident),*),)*) => ($(
+            impl<$($a: TryFrom<Value>),*> FromVecValue for ($($a,)*)
+                where $(anyhow::Error: From<$a::Error>,)*
+            {
+                #[allow(non_snake_case)]
+                fn from(list: Vec<Value>) -> anyhow::Result<Self> {
+                    let mut iter = list.into_iter();
+                    $(
+                        let $a = iter.next()
+                            .ok_or_else(|| anyhow::format_err!("not enough values"))?
+                            .try_into()?;
+                    )*
+                    if iter.next().is_some() {
+                        anyhow::bail!("too many return values");
+                    }
+                    Ok(($($a,)*))
+                }
+            }
+        )*)
+    }
+
+    tuple! {
+        (),
+        (A),
+        (A, B),
+        (A, B, C),
+    }
+}