Simplify lib.rs doc example (#1330)

simplify lib doc example

crates/wasmi/src/lib.rs

@@ -14,14 +14,11 @@
 //! [Wasmtime's API example](https://docs.rs/wasmtime/0.39.1/wasmtime/).
 //!
 //! ```
-//! use anyhow::Result;
 //! use wasmi::*;
-//! use wat;
 //!
-//! fn main() -> Result<()> {
-//!     // First step is to create the Wasm execution engine with some config.
-//!     // In this example we are using the default configuration.
-//!     let engine = Engine::default();
+//! // In this simple example we are going to compile the below Wasm source,
+//! // instantiate a Wasm module from it and call its exported "hello" function.
+//! fn main() -> anyhow::Result<()> {
 //!     let wasm = r#"
 //!         (module
 //!             (import "host" "hello" (func $host_hello (param i32)))
@@ -30,35 +27,34 @@
 //!             )
 //!         )
 //!     "#;
+//!     // First step is to create the Wasm execution engine with some config.
+//!     //
+//!     // In this example we are using the default configuration.
+//!     let engine = Engine::default();
+//!     // Now we can compile the above Wasm module with the given Wasm source.
 //!     let module = Module::new(&engine, wasm)?;
 //!
-//!     // All Wasm objects operate within the context of a `Store`.
-//!     // Each `Store` has a type parameter to store host-specific data,
-//!     // which in this case we are using `42` for.
+//!     // Wasm objects operate within the context of a Wasm `Store`.
+//!     //
+//!     // Each `Store` has a type parameter to store host specific data.
+//!     // In this example the host state is a simple `u32` type with value `42`.
 //!     type HostState = u32;
 //!     let mut store = Store::new(&engine, 42);
-//!     let host_hello = Func::wrap(&mut store, |caller: Caller<'_, HostState>, param: i32| {
-//!         println!("Got {param} from WebAssembly");
-//!         println!("My host state is: {}", caller.data());
-//!     });
 //!
-//!     // In order to create Wasm module instances and link their imports
-//!     // and exports we require a `Linker`.
+//!     // A linker can be used to instantiate Wasm modules.
+//!     // The job of a linker is to satisfy the Wasm module's imports.
 //!     let mut linker = <Linker<HostState>>::new(&engine);
-//!     // Instantiation of a Wasm module requires defining its imports and then
-//!     // afterwards we can fetch exports by name, as well as asserting the
-//!     // type signature of the function with `get_typed_func`.
-//!     //
-//!     // Also before using an instance created this way we need to start it.
-//!     linker.define("host", "hello", host_hello)?;
+//!     // We are required to define all imports before instantiating a Wasm module.
+//!     linker.func_wrap("host", "hello", |caller: Caller<'_, HostState>, param: i32| {
+//!         println!("Got {param} from WebAssembly and my host state is: {}", caller.data());
+//!     });
 //!     let instance = linker
 //!         .instantiate(&mut store, &module)?
 //!         .start(&mut store)?;
-//!     let hello = instance.get_typed_func::<(), ()>(&store, "hello")?;
-//!
-//!     // And finally we can call the wasm!
-//!     hello.call(&mut store, ())?;
-//!
+//!     // Now we can finally query the exported "hello" function and call it.
+//!     instance
+//!         .get_typed_func::<(), ()>(&store, "hello")?
+//!         .call(&mut store, ())?;
 //!     Ok(())
 //! }
 //! ```