diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9a6e926..1ebb3d60 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ New features
 
 * A new feature, `no_custom_syntax`, is added to remove custom syntax support from Rhai for applications that do not require it (which should be most).
 * Comment lines beginning with `//!` (requires the `metadata` feature) are now collected as the script file's _module documentation_.
+* `AST` and `Module` have methods to access and manipulate documentation.
 
 Enhancements
 ------------
@@ -34,6 +35,7 @@ Enhancements
 * A new `range` function variant that takes an exclusive range with a step.
 * `as_string` is added to BLOB's to convert it into a string by interpreting it as a UTF-8 byte stream.
 * `FnAccess::is_private`, `FnAccess::is_public`, `FnNamespace::is_module_namespace` and `FnNameSpace::is_global_namespace` are added for convenience.
+* `Iterator<Item=T>` type for functions metadata is simplified to `Iterator<T>`.
 
 
 Version 1.8.0
diff --git a/Cargo.toml b/Cargo.toml
index 7678fb27..9d421c64 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -82,6 +82,10 @@ name = "rhai-run"
 name = "rhai-dbg"
 required-features = ["debugging"]
 
+[[example]]
+name = "serde"
+required-features = ["serde"]
+
 [profile.release]
 lto = "fat"
 codegen-units = 1
diff --git a/examples/arrays_and_structs.rs b/examples/arrays_and_structs.rs
index 1cfeac47..fc937bcd 100644
--- a/examples/arrays_and_structs.rs
+++ b/examples/arrays_and_structs.rs
@@ -1,5 +1,10 @@
 //! An example showing how to register a Rust type and use it with arrays.
 
+#[cfg(any(feature = "no_index", feature = "no_object"))]
+fn main() {
+    panic!("This example does not run under 'no_index' or 'no_object'.")
+}
+
 use rhai::{Engine, EvalAltResult};
 
 #[cfg(not(feature = "no_index"))]
@@ -60,8 +65,3 @@ fn main() -> Result<(), Box<EvalAltResult>> {
 
     Ok(())
 }
-
-#[cfg(any(feature = "no_index", feature = "no_object"))]
-fn main() {
-    panic!("This example does not run under 'no_index' or 'no_object'.")
-}
diff --git a/examples/custom_types_and_methods.rs b/examples/custom_types_and_methods.rs
index e8261a73..a70265ff 100644
--- a/examples/custom_types_and_methods.rs
+++ b/examples/custom_types_and_methods.rs
@@ -1,5 +1,10 @@
 //! An example showing how to register a Rust type and methods/getters/setters for it.
 
+#[cfg(feature = "no_object")]
+fn main() {
+    panic!("This example does not run under 'no_object'.");
+}
+
 use rhai::{Engine, EvalAltResult};
 
 #[cfg(not(feature = "no_object"))]
@@ -61,8 +66,3 @@ fn main() -> Result<(), Box<EvalAltResult>> {
 
     Ok(())
 }
-
-#[cfg(feature = "no_object")]
-fn main() {
-    panic!("This example does not run under 'no_object'.");
-}
diff --git a/examples/event_handler_js/main.rs b/examples/event_handler_js/main.rs
index 99118feb..db5740f3 100644
--- a/examples/event_handler_js/main.rs
+++ b/examples/event_handler_js/main.rs
@@ -1,43 +1,45 @@
 //! Implementation of the Event Handler With State Pattern - JS Style
-use rhai::{Dynamic, Engine, Scope, AST};
 
-#[cfg(not(feature = "no_object"))]
-use rhai::Map;
-
-use std::io::{stdin, stdout, Write};
-
-const SCRIPT_FILE: &str = "event_handler_js/script.rhai";
-
-#[derive(Debug)]
-struct Handler {
-    pub engine: Engine,
-    pub scope: Scope<'static>,
-    pub states: Dynamic,
-    pub ast: AST,
-}
-
-fn print_scope(scope: &Scope) {
-    for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
-        #[cfg(not(feature = "no_closure"))]
-        let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
-        #[cfg(feature = "no_closure")]
-        let value_is_shared = "";
-
-        println!(
-            "[{}] {}{}{} = {:?}",
-            i + 1,
-            if constant { "const " } else { "" },
-            name,
-            value_is_shared,
-            *value.read_lock::<Dynamic>().unwrap(),
-        )
-    }
-    println!();
+#[cfg(any(feature = "no_function", feature = "no_object"))]
+pub fn main() {
+    panic!("This example does not run under 'no_function' or 'no_object'.")
 }
 
 #[cfg(not(feature = "no_function"))]
 #[cfg(not(feature = "no_object"))]
 pub fn main() {
+    use rhai::{Dynamic, Engine, Map, Scope, AST};
+    use std::io::{stdin, stdout, Write};
+
+    const SCRIPT_FILE: &str = "event_handler_js/script.rhai";
+
+    #[derive(Debug)]
+    struct Handler {
+        pub engine: Engine,
+        pub scope: Scope<'static>,
+        pub states: Dynamic,
+        pub ast: AST,
+    }
+
+    fn print_scope(scope: &Scope) {
+        for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
+            #[cfg(not(feature = "no_closure"))]
+            let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
+            #[cfg(feature = "no_closure")]
+            let value_is_shared = "";
+
+            println!(
+                "[{}] {}{}{} = {:?}",
+                i + 1,
+                if constant { "const " } else { "" },
+                name,
+                value_is_shared,
+                *value.read_lock::<Dynamic>().unwrap(),
+            )
+        }
+        println!();
+    }
+
     println!("Events Handler Example - JS Style");
     println!("==================================");
 
@@ -158,8 +160,3 @@ pub fn main() {
 
     println!("Bye!");
 }
-
-#[cfg(any(feature = "no_function", feature = "no_object"))]
-pub fn main() {
-    panic!("This example does not run under 'no_function' or 'no_object'.")
-}
diff --git a/examples/event_handler_main/main.rs b/examples/event_handler_main/main.rs
index 76348974..bc64a8b6 100644
--- a/examples/event_handler_main/main.rs
+++ b/examples/event_handler_main/main.rs
@@ -1,38 +1,43 @@
 //! Implementation of the Event Handler With State Pattern - Main Style
-use rhai::{Dynamic, Engine, Scope, AST};
 
-use std::io::{stdin, stdout, Write};
-
-const SCRIPT_FILE: &str = "event_handler_main/script.rhai";
-
-#[derive(Debug)]
-struct Handler {
-    pub engine: Engine,
-    pub scope: Scope<'static>,
-    pub ast: AST,
-}
-
-fn print_scope(scope: &Scope) {
-    for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
-        #[cfg(not(feature = "no_closure"))]
-        let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
-        #[cfg(feature = "no_closure")]
-        let value_is_shared = "";
-
-        println!(
-            "[{}] {}{}{} = {:?}",
-            i + 1,
-            if constant { "const " } else { "" },
-            name,
-            value_is_shared,
-            *value.read_lock::<Dynamic>().unwrap(),
-        )
-    }
-    println!();
+#[cfg(feature = "no_function")]
+pub fn main() {
+    panic!("This example does not run under 'no_function'.")
 }
 
 #[cfg(not(feature = "no_function"))]
 pub fn main() {
+    use rhai::{Dynamic, Engine, Scope, AST};
+    use std::io::{stdin, stdout, Write};
+
+    const SCRIPT_FILE: &str = "event_handler_main/script.rhai";
+
+    #[derive(Debug)]
+    struct Handler {
+        pub engine: Engine,
+        pub scope: Scope<'static>,
+        pub ast: AST,
+    }
+
+    fn print_scope(scope: &Scope) {
+        for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
+            #[cfg(not(feature = "no_closure"))]
+            let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
+            #[cfg(feature = "no_closure")]
+            let value_is_shared = "";
+
+            println!(
+                "[{}] {}{}{} = {:?}",
+                i + 1,
+                if constant { "const " } else { "" },
+                name,
+                value_is_shared,
+                *value.read_lock::<Dynamic>().unwrap(),
+            )
+        }
+        println!();
+    }
+
     println!("Events Handler Example - Main Style");
     println!("===================================");
 
@@ -130,8 +135,3 @@ pub fn main() {
 
     println!("Bye!");
 }
-
-#[cfg(feature = "no_function")]
-pub fn main() {
-    panic!("This example does not run under 'no_function'.")
-}
diff --git a/examples/event_handler_map/main.rs b/examples/event_handler_map/main.rs
index 1e7d1102..ad27e8ea 100644
--- a/examples/event_handler_map/main.rs
+++ b/examples/event_handler_map/main.rs
@@ -1,42 +1,44 @@
 //! Implementation of the Event Handler With State Pattern - Map Style
-use rhai::{Dynamic, Engine, Scope, AST};
 
-#[cfg(not(feature = "no_object"))]
-use rhai::Map;
-
-use std::io::{stdin, stdout, Write};
-
-const SCRIPT_FILE: &str = "event_handler_map/script.rhai";
-
-#[derive(Debug)]
-struct Handler {
-    pub engine: Engine,
-    pub scope: Scope<'static>,
-    pub ast: AST,
-}
-
-fn print_scope(scope: &Scope) {
-    for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
-        #[cfg(not(feature = "no_closure"))]
-        let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
-        #[cfg(feature = "no_closure")]
-        let value_is_shared = "";
-
-        println!(
-            "[{}] {}{}{} = {:?}",
-            i + 1,
-            if constant { "const " } else { "" },
-            name,
-            value_is_shared,
-            *value.read_lock::<Dynamic>().unwrap(),
-        )
-    }
-    println!();
+#[cfg(any(feature = "no_function", feature = "no_object"))]
+pub fn main() {
+    panic!("This example does not run under 'no_function' or 'no_object'.")
 }
 
 #[cfg(not(feature = "no_function"))]
 #[cfg(not(feature = "no_object"))]
 pub fn main() {
+    use rhai::{Dynamic, Engine, Map, Scope, AST};
+    use std::io::{stdin, stdout, Write};
+
+    const SCRIPT_FILE: &str = "event_handler_map/script.rhai";
+
+    #[derive(Debug)]
+    struct Handler {
+        pub engine: Engine,
+        pub scope: Scope<'static>,
+        pub ast: AST,
+    }
+
+    fn print_scope(scope: &Scope) {
+        for (i, (name, constant, value)) in scope.iter_raw().enumerate() {
+            #[cfg(not(feature = "no_closure"))]
+            let value_is_shared = if value.is_shared() { " (shared)" } else { "" };
+            #[cfg(feature = "no_closure")]
+            let value_is_shared = "";
+
+            println!(
+                "[{}] {}{}{} = {:?}",
+                i + 1,
+                if constant { "const " } else { "" },
+                name,
+                value_is_shared,
+                *value.read_lock::<Dynamic>().unwrap(),
+            )
+        }
+        println!();
+    }
+
     println!("Events Handler Example - Map Style");
     println!("==================================");
 
@@ -147,8 +149,3 @@ pub fn main() {
 
     println!("Bye!");
 }
-
-#[cfg(any(feature = "no_function", feature = "no_object"))]
-pub fn main() {
-    panic!("This example does not run under 'no_function' or 'no_object'.")
-}
diff --git a/examples/serde.rs b/examples/serde.rs
index 625bb5f6..b145e247 100644
--- a/examples/serde.rs
+++ b/examples/serde.rs
@@ -1,22 +1,12 @@
 //! An example to serialize and deserialize Rust types.
 
-#[cfg(any(not(feature = "serde"), feature = "no_object"))]
+#[cfg(feature = "no_object")]
 fn main() {
-    println!("This example requires the 'serde' feature to run.");
-    println!("Try: cargo run --features serde --example serde");
+    panic!("This example does not run under 'no_object'.")
 }
 
-#[cfg(feature = "serde")]
 #[cfg(not(feature = "no_object"))]
 fn main() {
-    example::ser();
-    println!();
-    example::de();
-}
-
-#[cfg(feature = "serde")]
-#[cfg(not(feature = "no_object"))]
-mod example {
     use rhai::serde::{from_dynamic, to_dynamic};
     use rhai::{Dynamic, Engine, Map};
     use serde::{Deserialize, Serialize};
@@ -60,13 +50,13 @@ mod example {
         let result: Dynamic = engine
             .eval(
                 r#"
-                    #{
-                        a: 42,
-                        b: [ "hello", "world" ],
-                        c: true,
-                        d: #{ x: 123.456, y: 999.0 }
-                    }
-                "#,
+                        #{
+                            a: 42,
+                            b: [ "hello", "world" ],
+                            c: true,
+                            d: #{ x: 123.456, y: 999.0 }
+                        }
+                    "#,
             )
             .unwrap();
 
@@ -89,4 +79,8 @@ mod example {
         );
         println!("Deserialized to struct: {:#?}", x);
     }
+
+    ser();
+    println!();
+    de();
 }
diff --git a/src/api/compile.rs b/src/api/compile.rs
index b9e95e50..78424402 100644
--- a/src/api/compile.rs
+++ b/src/api/compile.rs
@@ -222,10 +222,10 @@ impl Engine {
             self.token_mapper.as_ref().map(<_>::as_ref),
         );
         let mut state = ParseState::new(self, scope, tokenizer_control);
-        let mut ast = self.parse(&mut stream.peekable(), &mut state, optimization_level)?;
+        let mut _ast = self.parse(&mut stream.peekable(), &mut state, optimization_level)?;
         #[cfg(feature = "metadata")]
-        ast.set_doc(state.tokenizer_control.borrow().global_comments.join("\n"));
-        Ok(ast)
+        _ast.set_doc(state.tokenizer_control.borrow().global_comments.join("\n"));
+        Ok(_ast)
     }
     /// Compile a string containing an expression into an [`AST`],
     /// which can be used later for evaluation.
diff --git a/src/api/optimize.rs b/src/api/optimize.rs
index 726b12f9..f790a803 100644
--- a/src/api/optimize.rs
+++ b/src/api/optimize.rs
@@ -2,7 +2,6 @@
 #![cfg(not(feature = "no_optimize"))]
 
 use crate::{Engine, OptimizationLevel, Scope, AST};
-use std::mem;
 
 impl Engine {
     /// Control whether and how the [`Engine`] will optimize an [`AST`] after compilation.
@@ -60,7 +59,7 @@ impl Engine {
             .map(|f| f.func.get_script_fn_def().unwrap().clone())
             .collect();
 
-        let mut new_ast = crate::optimizer::optimize_into_ast(
+        let mut _new_ast = crate::optimizer::optimize_into_ast(
             self,
             scope,
             ast.take_statements(),
@@ -70,8 +69,8 @@ impl Engine {
         );
 
         #[cfg(feature = "metadata")]
-        new_ast.set_doc(mem::take(ast.doc_mut()));
+        _new_ast.set_doc(std::mem::take(ast.doc_mut()));
 
-        new_ast
+        _new_ast
     }
 }
diff --git a/src/ast/ast.rs b/src/ast/ast.rs
index 0c201593..854ce431 100644
--- a/src/ast/ast.rs
+++ b/src/ast/ast.rs
@@ -1,7 +1,7 @@
 //! Module defining the AST (abstract syntax tree).
 
 use super::{ASTFlags, Expr, FnAccess, Stmt, StmtBlock, StmtBlockContainer};
-use crate::{Dynamic, FnNamespace, Identifier, Position, SmartString};
+use crate::{Dynamic, FnNamespace, Identifier, Position};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 use std::{
@@ -23,7 +23,7 @@ pub struct AST {
     source: Identifier,
     /// [`AST`] documentation.
     #[cfg(feature = "metadata")]
-    doc: SmartString,
+    doc: crate::SmartString,
     /// Global statements.
     body: StmtBlock,
     /// Script-defined functions.
@@ -76,7 +76,7 @@ impl AST {
         Self {
             source: Identifier::new_const(),
             #[cfg(feature = "metadata")]
-            doc: SmartString::new_const(),
+            doc: crate::SmartString::new_const(),
             body: StmtBlock::new(statements, Position::NONE, Position::NONE),
             #[cfg(not(feature = "no_function"))]
             lib: functions.into(),
@@ -96,7 +96,7 @@ impl AST {
         Self {
             source: Identifier::new_const(),
             #[cfg(feature = "metadata")]
-            doc: SmartString::new_const(),
+            doc: crate::SmartString::new_const(),
             body: StmtBlock::new(statements, Position::NONE, Position::NONE),
             #[cfg(not(feature = "no_function"))]
             lib: functions.into(),
@@ -146,7 +146,7 @@ impl AST {
         Self {
             source: Identifier::new_const(),
             #[cfg(feature = "metadata")]
-            doc: SmartString::new_const(),
+            doc: crate::SmartString::new_const(),
             body: StmtBlock::NONE,
             #[cfg(not(feature = "no_function"))]
             lib: crate::Module::new().into(),
@@ -195,6 +195,7 @@ impl AST {
     /// Leading white-spaces are stripped, and each line always starts with `//!`.
     #[cfg(feature = "metadata")]
     #[inline(always)]
+    #[must_use]
     pub fn doc(&self) -> &str {
         &self.doc
     }
@@ -211,7 +212,8 @@ impl AST {
     /// Only available under `metadata`.
     #[cfg(feature = "metadata")]
     #[inline(always)]
-    pub(crate) fn doc_mut(&mut self) -> &mut SmartString {
+    #[must_use]
+    pub(crate) fn doc_mut(&mut self) -> &mut crate::SmartString {
         &mut self.doc
     }
     /// Set the documentation.
@@ -219,7 +221,7 @@ impl AST {
     /// Only available under `metadata`.
     #[cfg(feature = "metadata")]
     #[inline(always)]
-    pub(crate) fn set_doc(&mut self, doc: impl Into<SmartString>) {
+    pub(crate) fn set_doc(&mut self, doc: impl Into<crate::SmartString>) {
         self.doc = doc.into();
     }
     /// Get the statements.
diff --git a/src/ast/stmt.rs b/src/ast/stmt.rs
index c2cad9da..ae9b064a 100644
--- a/src/ast/stmt.rs
+++ b/src/ast/stmt.rs
@@ -260,7 +260,7 @@ impl RangeCase {
             Self::InclusiveInt(..) => true,
         }
     }
-    /// Get the index to the [`ConditionalStmtBlock`].
+    /// Get the index to the [`ConditionalExpr`].
     #[inline(always)]
     #[must_use]
     pub fn index(&self) -> usize {
@@ -268,7 +268,7 @@ impl RangeCase {
             Self::ExclusiveInt(.., n) | Self::InclusiveInt(.., n) => *n,
         }
     }
-    /// Set the index to the [`ConditionalStmtBlock`].
+    /// Set the index to the [`ConditionalExpr`].
     #[inline(always)]
     pub fn set_index(&mut self, index: usize) {
         match self {
diff --git a/src/lib.rs b/src/lib.rs
index e476fb15..7b8c9cff 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -272,8 +272,8 @@ pub use tokenizer::{get_next_token, parse_string_literal};
 
 #[cfg(feature = "internals")]
 pub use tokenizer::{
-    InputStream, MultiInputsStream, Span, Token, TokenIterator, TokenizeState, TokenizerControl,
-    TokenizerControlBlock,
+    is_valid_function_name, is_valid_identifier, InputStream, MultiInputsStream, Span, Token,
+    TokenIterator, TokenizeState, TokenizerControl, TokenizerControlBlock,
 };
 
 #[cfg(feature = "internals")]
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 38bb887a..01ac556d 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -250,6 +250,9 @@ pub struct Module {
     /// ID identifying the module.
     /// No ID if string is empty.
     id: Identifier,
+    /// Module documentation.
+    #[cfg(feature = "metadata")]
+    doc: crate::SmartString,
     /// Is this module internal?
     pub(crate) internal: bool,
     /// Is this module part of a standard library?
@@ -290,31 +293,27 @@ impl fmt::Debug for Module {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut d = f.debug_struct("Module");
 
-        if !self.id.is_empty() {
-            d.field("id", &self.id);
-        }
-        if !self.modules.is_empty() {
-            d.field(
+        d.field("id", &self.id)
+            .field(
                 "modules",
                 &self
                     .modules
                     .keys()
                     .map(|m| m.as_str())
                     .collect::<BTreeSet<_>>(),
-            );
-        }
-        if !self.variables.is_empty() {
-            d.field("vars", &self.variables);
-        }
-        if !self.functions.is_empty() {
-            d.field(
+            )
+            .field("vars", &self.variables)
+            .field(
                 "functions",
                 &self
                     .iter_fn()
                     .map(|f| f.func.to_string())
                     .collect::<BTreeSet<_>>(),
             );
-        }
+
+        #[cfg(feature = "metadata")]
+        d.field("doc", &self.doc);
+
         d.finish()
     }
 }
@@ -363,6 +362,8 @@ impl Module {
     pub fn new() -> Self {
         Self {
             id: Identifier::new_const(),
+            #[cfg(feature = "metadata")]
+            doc: crate::SmartString::new_const(),
             internal: false,
             standard: false,
             custom_types: CustomTypesCollection::new(),
@@ -423,6 +424,7 @@ impl Module {
         self.id = id.into();
         self
     }
+
     /// Clear the ID of the [`Module`].
     ///
     /// # Example
@@ -441,10 +443,69 @@ impl Module {
         self
     }
 
+    /// Get the documentation of the [`Module`], if any.
+    /// Exported under the `metadata` feature only.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rhai::Module;
+    /// let mut module = Module::new();
+    /// module.set_doc("//! This is my special module.");
+    /// assert_eq!(module.doc(), "//! This is my special module.");
+    /// ```
+    #[cfg(feature = "metadata")]
+    #[inline]
+    #[must_use]
+    pub fn doc(&self) -> &str {
+        &self.doc
+    }
+
+    /// Set the documentation of the [`Module`].
+    /// Exported under the `metadata` feature only.
+    ///
+    /// If the string is empty, it is equivalent to clearing the documentation.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rhai::Module;
+    /// let mut module = Module::new();
+    /// module.set_doc("//! This is my special module.");
+    /// assert_eq!(module.doc(), "//! This is my special module.");
+    /// ```
+    #[cfg(feature = "metadata")]
+    #[inline(always)]
+    pub fn set_doc(&mut self, doc: impl Into<crate::SmartString>) -> &mut Self {
+        self.doc = doc.into();
+        self
+    }
+
+    /// Clear the documentation of the [`Module`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rhai::Module;
+    /// let mut module = Module::new();
+    /// module.set_doc("//! This is my special module.");
+    /// assert_eq!(module.doc(), "//! This is my special module.");
+    /// module.clear_doc();
+    /// assert_eq!(module.doc(), "");
+    /// ```
+    #[cfg(feature = "metadata")]
+    #[inline(always)]
+    pub fn clear_doc(&mut self) -> &mut Self {
+        self.doc.clear();
+        self
+    }
+
     /// Clear the [`Module`].
     #[inline(always)]
     pub fn clear(&mut self) {
         self.id.clear();
+        #[cfg(feature = "metadata")]
+        self.doc.clear();
         self.internal = false;
         self.standard = false;
         self.custom_types.clear();
@@ -1563,6 +1624,15 @@ impl Module {
         self.all_type_iterators.clear();
         self.indexed = false;
         self.contains_indexed_global_functions = false;
+
+        #[cfg(feature = "metadata")]
+        if !other.doc.is_empty() {
+            if !self.doc.is_empty() {
+                self.doc.push('\n');
+            }
+            self.doc.push_str(&other.doc);
+        }
+
         self
     }
 
@@ -1584,6 +1654,15 @@ impl Module {
         self.all_type_iterators.clear();
         self.indexed = false;
         self.contains_indexed_global_functions = false;
+
+        #[cfg(feature = "metadata")]
+        if !other.doc.is_empty() {
+            if !self.doc.is_empty() {
+                self.doc.push('\n');
+            }
+            self.doc.push_str(&other.doc);
+        }
+
         self
     }
 
@@ -1614,6 +1693,15 @@ impl Module {
         self.all_type_iterators.clear();
         self.indexed = false;
         self.contains_indexed_global_functions = false;
+
+        #[cfg(feature = "metadata")]
+        if !other.doc.is_empty() {
+            if !self.doc.is_empty() {
+                self.doc.push('\n');
+            }
+            self.doc.push_str(&other.doc);
+        }
+
         self
     }
 
@@ -1667,6 +1755,15 @@ impl Module {
         self.all_type_iterators.clear();
         self.indexed = false;
         self.contains_indexed_global_functions = false;
+
+        #[cfg(feature = "metadata")]
+        if !other.doc.is_empty() {
+            if !self.doc.is_empty() {
+                self.doc.push('\n');
+            }
+            self.doc.push_str(&other.doc);
+        }
+
         self
     }
 
@@ -1978,6 +2075,9 @@ impl Module {
 
         module.set_id(ast.source_raw().clone());
 
+        #[cfg(feature = "metadata")]
+        module.set_doc(ast.doc());
+
         module.build_index();
 
         Ok(module)
diff --git a/src/packages/iter_basic.rs b/src/packages/iter_basic.rs
index 4f6d4317..28304579 100644
--- a/src/packages/iter_basic.rs
+++ b/src/packages/iter_basic.rs
@@ -248,7 +248,7 @@ macro_rules! reg_range {
             $lib.update_fn_metadata_with_comments(_hash, [
                     concat!("from: ", stringify!($y)),
                     concat!("to: ", stringify!($y)),
-                    concat!("Iterator<Item=", stringify!($y), ">"),
+                    concat!("Iterator<", stringify!($y), ">"),
             ], [
                 "/// Return an iterator over the exclusive range of `from..to`.",
                 "/// The value `to` is never included.",
@@ -282,7 +282,7 @@ macro_rules! reg_range {
                     concat!("from: ", stringify!($y)),
                     concat!("to: ", stringify!($y)),
                     concat!("step: ", stringify!($y)),
-                    concat!("Iterator<Item=", stringify!($y), ">")
+                    concat!("Iterator<", stringify!($y), ">")
             ], [
                 "/// Return an iterator over the exclusive range of `from..to`, each iteration increasing by `step`.",
                 "/// The value `to` is never included.",
@@ -312,7 +312,7 @@ macro_rules! reg_range {
             $lib.update_fn_metadata_with_comments(_hash, [
                     concat!("range: Range<", stringify!($y), ">"),
                     concat!("step: ", stringify!($y)),
-                    concat!("Iterator<Item=", stringify!($y), ">")
+                    concat!("Iterator<", stringify!($y), ">")
             ], [
                 "/// Return an iterator over an exclusive range, each iteration increasing by `step`.",
                 "///",
@@ -388,7 +388,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["string: &str", &range_type, "Iterator<Item=char>"],
+            ["string: &str", &range_type, "Iterator<char>"],
             [
                 "/// Return an iterator over an exclusive range of characters in the string.",
                 "///",
@@ -410,7 +410,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["string: &str", &range_inclusive_type, "Iterator<Item=char>"],
+            ["string: &str", &range_inclusive_type, "Iterator<char>"],
             [
                 "/// Return an iterator over an inclusive range of characters in the string.",
                 "///",
@@ -428,7 +428,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["string: &str", "start: INT", "len: INT", "Iterator<Item=char>"],
+            ["string: &str", "start: INT", "len: INT", "Iterator<char>"],
             [
                 "/// Return an iterator over a portion of characters in the string.",
                 "///",
@@ -452,7 +452,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["string: &str", "from: INT", "Iterator<Item=char>"],
+            ["string: &str", "from: INT", "Iterator<char>"],
             [
                 "/// Return an iterator over the characters in the string starting from the `start` position.",
                 "///",
@@ -474,7 +474,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["string: &str", "Iterator<Item=char>"],
+            ["string: &str", "Iterator<char>"],
             [
                 "/// Return an iterator over the characters in the string.",
                 "///",
@@ -494,7 +494,7 @@ def_package! {
             #[cfg(feature = "metadata")]
             lib.update_fn_metadata_with_comments(
                 _hash,
-                ["string: &mut ImmutableString", "Iterator<Item=char>"],
+                ["string: &mut ImmutableString", "Iterator<char>"],
                 [
                     "/// Return an iterator over all the characters in the string.",
                     "///",
@@ -520,7 +520,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["value: INT", &range_type, "Iterator<Item=bool>"],
+            ["value: INT", &range_type, "Iterator<bool>"],
             [
                 "/// Return an iterator over an exclusive range of bits in the number.",
                 "///",
@@ -544,7 +544,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["value: INT", &range_inclusive_type, "Iterator<Item=bool>"],
+            ["value: INT", &range_inclusive_type, "Iterator<bool>"],
             [
                 "/// Return an iterator over an inclusive range of bits in the number.",
                 "///",
@@ -564,7 +564,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["value: INT", "from: INT", "len: INT", "Iterator<Item=bool>"],
+            ["value: INT", "from: INT", "len: INT", "Iterator<bool>"],
             [
                 "/// Return an iterator over a portion of bits in the number.",
                 "///",
@@ -588,7 +588,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["value: INT", "from: INT", "Iterator<Item=bool>"],
+            ["value: INT", "from: INT", "Iterator<bool>"],
             [
                 "/// Return an iterator over the bits in the number starting from the specified `start` position.",
                 "///",
@@ -610,7 +610,7 @@ def_package! {
         #[cfg(feature = "metadata")]
         lib.update_fn_metadata_with_comments(
             _hash,
-            ["value: INT", "Iterator<Item=bool>"],
+            ["value: INT", "Iterator<bool>"],
             [
                 "/// Return an iterator over all the bits in the number.",
                 "///",
@@ -632,7 +632,7 @@ def_package! {
             #[cfg(feature = "metadata")]
             lib.update_fn_metadata_with_comments(
                 _hash,
-                ["value: &mut INT", "Iterator<Item=bool>"],
+                ["value: &mut INT", "Iterator<bool>"],
                 [
                     "/// Return an iterator over all the bits in the number.",
                     "///",
diff --git a/src/packages/lang_core.rs b/src/packages/lang_core.rs
index a82a5fa4..2390487d 100644
--- a/src/packages/lang_core.rs
+++ b/src/packages/lang_core.rs
@@ -174,6 +174,17 @@ fn collect_fn_metadata(
                 .collect::<Array>()
                 .into(),
         );
+        #[cfg(feature = "metadata")]
+        if !func.comments.is_empty() {
+            map.insert(
+                dict.get("comments").expect(DICT).clone(),
+                func.comments
+                    .iter()
+                    .map(|s| Into::into(&**s))
+                    .collect::<Array>()
+                    .into(),
+            );
+        }
 
         map
     }
@@ -188,6 +199,8 @@ fn collect_fn_metadata(
         "private",
         "is_anonymous",
         "params",
+        #[cfg(feature = "metadata")]
+        "comments",
     ]
     .iter()
     .map(|&s| s.into())
diff --git a/src/serde/metadata.rs b/src/serde/metadata.rs
index f430e484..4c8cc501 100644
--- a/src/serde/metadata.rs
+++ b/src/serde/metadata.rs
@@ -3,7 +3,7 @@
 #![cfg(feature = "metadata")]
 
 use crate::module::{calc_native_fn_hash, FuncInfo};
-use crate::{calc_fn_hash, Engine, AST};
+use crate::{calc_fn_hash, Engine, SmartString, AST};
 use serde::{Deserialize, Serialize};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -158,6 +158,9 @@ impl<'a> From<&'a FuncInfo> for FnMetadata<'a> {
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
 struct ModuleMetadata<'a> {
+    #[cfg(feature = "metadata")]
+    #[serde(skip_serializing_if = "SmartString::is_empty")]
+    pub doc: SmartString,
     #[serde(skip_serializing_if = "BTreeMap::is_empty")]
     pub modules: BTreeMap<&'a str, Self>,
     #[serde(skip_serializing_if = "Vec::is_empty")]
@@ -168,6 +171,8 @@ impl ModuleMetadata<'_> {
     #[inline(always)]
     pub fn new() -> Self {
         Self {
+            #[cfg(feature = "metadata")]
+            doc: SmartString::new_const(),
             modules: BTreeMap::new(),
             functions: Vec::new(),
         }
@@ -180,6 +185,7 @@ impl<'a> From<&'a crate::Module> for ModuleMetadata<'a> {
         functions.sort();
 
         Self {
+            doc: module.doc().into(),
             modules: module
                 .iter_sub_modules()
                 .map(|(name, m)| (name, m.as_ref().into()))
@@ -240,6 +246,11 @@ impl Engine {
 
         global.functions.sort();
 
+        #[cfg(feature = "metadata")]
+        {
+            global.doc = ast.doc().into();
+        }
+
         serde_json::to_string_pretty(&global)
     }
 
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 5b827c38..5cccd741 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -2179,7 +2179,7 @@ fn get_identifier(
     Some((Token::Identifier(identifier.into()), start_pos))
 }
 
-/// Is this keyword allowed as a function?
+/// Is a keyword allowed as a function?
 #[inline]
 #[must_use]
 pub fn is_keyword_function(name: &str) -> bool {
@@ -2194,7 +2194,8 @@ pub fn is_keyword_function(name: &str) -> bool {
     }
 }
 
-/// Is a text string a valid identifier?
+/// _(internals)_ Is a text string a valid identifier?
+/// Exported under the `internals` feature only.
 #[must_use]
 pub fn is_valid_identifier(name: impl Iterator<Item = char>) -> bool {
     let mut first_alphabetic = false;
@@ -2212,7 +2213,8 @@ pub fn is_valid_identifier(name: impl Iterator<Item = char>) -> bool {
     first_alphabetic
 }
 
-/// Is a text string a valid script-defined function name?
+/// _(internals)_ Is a text string a valid script-defined function name?
+/// Exported under the `internals` feature only.
 #[inline(always)]
 #[must_use]
 pub fn is_valid_function_name(name: &str) -> bool {