From 5748185fb7a9b13266a69e8f15420cf839cd70ca Mon Sep 17 00:00:00 2001
From: elkowar <5300871+elkowar@users.noreply.github.com>
Date: Tue, 20 Jul 2021 18:51:29 +0200
Subject: [PATCH] FromDynVal-trait

---
 src/dynval.rs | 54 ++++++++++++++++++++++++++++++++++-----------------
 src/eval.rs   | 21 +++++++++++++++-----
 2 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/src/dynval.rs b/src/dynval.rs
index b3b5b2b..463eae7 100644
--- a/src/dynval.rs
+++ b/src/dynval.rs
@@ -1,7 +1,7 @@
 use crate::ast::Span;
 use itertools::Itertools;
 use serde::{Deserialize, Serialize};
-use std::{convert::TryFrom, fmt, iter::FromIterator};
+use std::{fmt, iter::FromIterator, str::FromStr};
 
 pub type Result<T> = std::result::Result<T, ConversionError>;
 
@@ -34,7 +34,7 @@ impl From<String> for DynVal {
 
 impl fmt::Display for DynVal {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "\"{}\"", self.0)
+        write!(f, "{}", self.0)
     }
 }
 impl fmt::Debug for DynVal {
@@ -70,32 +70,46 @@ impl std::str::FromStr for DynVal {
     }
 }
 
-macro_rules! impl_try_from {
-    (impl From<$typ:ty> {
-        $(for $for:ty => |$arg:ident| $code:expr);*;
-    }) => {
-        $(impl TryFrom<$typ> for $for {
-            type Error = ConversionError;
-            fn try_from($arg: $typ) -> std::result::Result<Self, Self::Error> { $code }
+pub trait FromDynVal: Sized {
+    type Err;
+    fn from_dynval(x: &DynVal) -> std::result::Result<Self, Self::Err>;
+}
+
+impl<E, T: FromStr<Err = E>> FromDynVal for T {
+    type Err = E;
+
+    fn from_dynval(x: &DynVal) -> std::result::Result<Self, Self::Err> {
+        x.0.parse()
+    }
+}
+
+macro_rules! impl_from_dynval {
+    (
+        $(for $for:ty => |$name:ident| $code:expr);*;
+    ) => {
+        $(impl FromDynVal for $for {
+            type Err = ConversionError;
+            fn from_dynval($name: DynVal) -> std::result::Result<Self, Self::Err> { $code }
         })*
     };
 }
-macro_rules! impl_primval_from {
+macro_rules! impl_dynval_from {
     ($($t:ty),*) => {
         $(impl From<$t> for DynVal {
             fn from(x: $t) -> Self { DynVal(x.to_string(), None) }
         })*
     };
 }
-impl_try_from!(impl From<DynVal> {
-    for String => |x| x.as_string();
-    for f64 => |x| x.as_f64();
-    for i32 => |x| x.as_i32();
-    for bool => |x| x.as_bool();
-    //for Vec<String> => |x| x.as_vec();
-});
 
-impl_primval_from!(bool, i32, u32, f32, u8, f64, &str);
+// impl_from_dynval! {
+// for String => |x| x.as_string();
+// for f64 => |x| x.as_f64();
+// for i32 => |x| x.as_i32();
+// for bool => |x| x.as_bool();
+////for Vec<String> => |x| x.as_vec();
+//}
+
+impl_dynval_from!(bool, i32, u32, f32, u8, f64, &str);
 
 impl From<&serde_json::Value> for DynVal {
     fn from(v: &serde_json::Value) -> Self {
@@ -118,6 +132,10 @@ impl DynVal {
         DynVal(s, None)
     }
 
+    pub fn read_as<E, T: FromDynVal<Err = E>>(&self) -> std::result::Result<T, E> {
+        T::from_dynval(self)
+    }
+
     pub fn into_inner(self) -> String {
         self.0
     }
diff --git a/src/eval.rs b/src/eval.rs
index 01d58bd..3c70583 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -8,6 +8,9 @@ use std::collections::HashMap;
 
 #[derive(Debug, thiserror::Error)]
 pub enum EvalError {
+    #[error("Tried to reference variable `{0}`, but we cannot access variables here")]
+    NoVariablesAllowed(String),
+
     #[error("Invalid regex: {0}")]
     InvalidRegex(#[from] regex::Error),
 
@@ -114,12 +117,20 @@ impl SimplExpr {
         }
     }
 
-    pub fn eval(self, values: &HashMap<VarName, DynVal>) -> Result<DynVal, EvalError> {
+    pub fn eval_no_vars(&self) -> Result<DynVal, EvalError> {
+        match self.eval(&HashMap::new()) {
+            Ok(x) => Ok(x),
+            Err(EvalError::UnknownVariable(name)) => Err(EvalError::NoVariablesAllowed(name)),
+            Err(x) => Err(x),
+        }
+    }
+
+    pub fn eval(&self, values: &HashMap<VarName, DynVal>) -> Result<DynVal, EvalError> {
         let span = self.span();
         let value = match self {
-            SimplExpr::Literal(_, x) => Ok(x),
+            SimplExpr::Literal(_, x) => Ok(x.clone()),
             SimplExpr::VarRef(span, ref name) => {
-                Ok(values.get(name).cloned().ok_or_else(|| EvalError::UnresolvedVariable(name.to_string()).at(span))?.at(span))
+                Ok(values.get(name).cloned().ok_or_else(|| EvalError::UnresolvedVariable(name.to_string()).at(*span))?.at(*span))
             }
             SimplExpr::BinOp(_, a, op, b) => {
                 let a = a.eval(values)?;
@@ -176,12 +187,12 @@ impl SimplExpr {
                             .unwrap_or(&serde_json::Value::Null);
                         Ok(DynVal::from(indexed_value))
                     }
-                    _ => Err(EvalError::CannotIndex(format!("{}", val)).at(span)),
+                    _ => Err(EvalError::CannotIndex(format!("{}", val)).at(*span)),
                 }
             }
             SimplExpr::FunctionCall(span, function_name, args) => {
                 let args = args.into_iter().map(|a| a.eval(values)).collect::<Result<_, EvalError>>()?;
-                call_expr_function(&function_name, args).map_err(|e| e.at(span))
+                call_expr_function(&function_name, args).map_err(|e| e.at(*span))
             }
         };
         Ok(value?.at(span))