From d0711394f000d5254d9a0ec215f73c95961884ff Mon Sep 17 00:00:00 2001
From: Stephen Chung <Stephen.Chung@intexact.com>
Date: Mon, 6 Jul 2020 21:30:35 +0800
Subject: [PATCH] Expose FnPtr and move name checking into

---
 .gitignore       |  4 +++-
 src/engine.rs    | 18 ++++++------------
 src/fn_native.rs | 40 ++++++++++++++++++++++++++++++++++++----
 src/lib.rs       |  2 +-
 4 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/.gitignore b/.gitignore
index 140811c2..e884ce0f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,6 @@ target/
 Cargo.lock
 .vscode/
 .cargo/
-doc/book/
\ No newline at end of file
+doc/book/
+before
+after
diff --git a/src/engine.rs b/src/engine.rs
index e8a47960..f999235b 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -11,7 +11,7 @@ use crate::parser::{Expr, FnAccess, ImmutableString, ReturnType, ScriptFnDef, St
 use crate::r#unsafe::unsafe_cast_var_name_to_lifetime;
 use crate::result::EvalAltResult;
 use crate::scope::{EntryType as ScopeEntryType, Scope};
-use crate::token::{is_valid_identifier, Position};
+use crate::token::Position;
 use crate::utils::StaticVec;
 
 #[cfg(not(feature = "no_float"))]
@@ -22,6 +22,7 @@ use crate::stdlib::{
     borrow::Cow,
     boxed::Box,
     collections::{HashMap, HashSet},
+    convert::TryFrom,
     format,
     iter::{empty, once},
     mem,
@@ -1735,6 +1736,7 @@ impl Engine {
                         let expr = args_expr.get(0);
                         let arg_value =
                             self.eval_expr(scope, mods, state, lib, this_ptr, expr, level)?;
+
                         return arg_value
                             .take_immutable_string()
                             .map_err(|typ| {
@@ -1744,17 +1746,9 @@ impl Engine {
                                     expr.position(),
                                 ))
                             })
-                            .and_then(|s| {
-                                if is_valid_identifier(s.chars()) {
-                                    Ok(s)
-                                } else {
-                                    Err(Box::new(EvalAltResult::ErrorFunctionNotFound(
-                                        s.to_string(),
-                                        expr.position(),
-                                    )))
-                                }
-                            })
-                            .map(|s| FnPtr::from(s).into());
+                            .and_then(|s| FnPtr::try_from(s))
+                            .map(Into::<Dynamic>::into)
+                            .map_err(|err| err.new_position(*pos));
                     }
                 }
 
diff --git a/src/fn_native.rs b/src/fn_native.rs
index 49cb4570..be4d6593 100644
--- a/src/fn_native.rs
+++ b/src/fn_native.rs
@@ -3,9 +3,10 @@ use crate::engine::Engine;
 use crate::module::Module;
 use crate::parser::ScriptFnDef;
 use crate::result::EvalAltResult;
+use crate::token::{is_valid_identifier, Position};
 use crate::utils::ImmutableString;
 
-use crate::stdlib::{boxed::Box, fmt, rc::Rc, sync::Arc};
+use crate::stdlib::{boxed::Box, convert::TryFrom, fmt, rc::Rc, sync::Arc};
 
 /// Trait that maps to `Send + Sync` only under the `sync` feature.
 #[cfg(feature = "sync")]
@@ -52,6 +53,10 @@ pub type FnCallArgs<'a> = [&'a mut Dynamic];
 pub struct FnPtr(ImmutableString);
 
 impl FnPtr {
+    /// Create a new function pointer.
+    pub(crate) fn new<S: Into<ImmutableString>>(name: S) -> Self {
+        Self(name.into())
+    }
     /// Get the name of the function.
     pub fn fn_name(&self) -> &str {
         self.get_fn_name().as_ref()
@@ -72,9 +77,36 @@ impl fmt::Display for FnPtr {
     }
 }
 
-impl<S: Into<ImmutableString>> From<S> for FnPtr {
-    fn from(value: S) -> Self {
-        Self(value.into())
+impl TryFrom<ImmutableString> for FnPtr {
+    type Error = Box<EvalAltResult>;
+
+    fn try_from(value: ImmutableString) -> Result<Self, Self::Error> {
+        if is_valid_identifier(value.chars()) {
+            Ok(Self(value))
+        } else {
+            Err(Box::new(EvalAltResult::ErrorFunctionNotFound(
+                value.to_string(),
+                Position::none(),
+            )))
+        }
+    }
+}
+
+impl TryFrom<String> for FnPtr {
+    type Error = Box<EvalAltResult>;
+
+    fn try_from(value: String) -> Result<Self, Self::Error> {
+        let s: ImmutableString = value.into();
+        Self::try_from(s)
+    }
+}
+
+impl TryFrom<&str> for FnPtr {
+    type Error = Box<EvalAltResult>;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        let s: ImmutableString = value.into();
+        Self::try_from(s)
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 13221e2c..768ad25a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -98,7 +98,7 @@ mod utils;
 pub use any::Dynamic;
 pub use engine::Engine;
 pub use error::{ParseError, ParseErrorType};
-pub use fn_native::IteratorFn;
+pub use fn_native::{FnPtr, IteratorFn};
 pub use fn_register::{RegisterFn, RegisterResultFn};
 pub use module::Module;
 pub use parser::{ImmutableString, AST, INT};