Prefix dereferences as lvalues

forge_core/src/ast.rs

@@ -79,26 +79,20 @@ pub struct Assignment {
 }
 
 #[derive(PartialEq, Clone, Debug)]
-pub struct Lvalue {
-    pub name: String,
-    pub subscripts: Vec<Suffix>,
+pub enum Lvalue {
+    Expr(BoxExpr),
+    Name(String, Vec<Suffix>)
 }
 
 impl From<&str> for Lvalue {
     fn from(name: &str) -> Self {
-        Self {
-            name: String::from(name),
-            subscripts: vec![],
-        }
+        Self::Name(String::from(name), vec![])
     }
 }
 
 impl From<String> for Lvalue {
     fn from(name: String) -> Self {
-        Self {
-            name,
-            subscripts: vec![],
-        }
+        Self::Name(name, vec![])
     }
 }
 

forge_core/src/compiler.rs

@@ -317,35 +317,43 @@ impl Compilable for Lvalue {
         let global_scope = &state.global_scope;
         let mut sig = sig.expect("lvalue outside a function");
 
-        if !self.subscripts.is_empty() {
-            todo!("Arrays and structs aren't implemented yet")
-        }
+        match self {
+            Self::Name(name, subscripts) => {
+                if !subscripts.is_empty() {
+                    todo!("Arrays and structs aren't implemented yet")
+                }
 
-        if let Some(var) = lookup(&self.name, global_scope, &sig.local_scope) {
-            match var {
-                Variable::Literal(_) | Variable::DirectLabel(_) => {
-                    // Direct labels are (probably) functions, the important part is the
-                    // label itself, which we can't alter, so, error:
-                    Err(CompileError(0, 0, format!("Invalid lvalue {}", self.name)))
-                }
-                Variable::IndirectLabel(label) => {
-                    // Indirect labels are variables, the label is where the data is stored,
-                    // so we push that label so we can store stuff there
-                    let label = label.clone();
-                    sig.emit_arg("push", label);
-                    Ok(())
-                }
-                Variable::Local(offset) => {
-                    let offset = *offset;
-                    sig.emit_arg("loadw", "frame");
-                    if offset > 0 {
-                        sig.emit_arg("add", offset);
+                if let Some(var) = lookup(&name, global_scope, &sig.local_scope) {
+                    match var {
+                        Variable::Literal(_) | Variable::DirectLabel(_) => {
+                            // Direct labels are (probably) functions, the important part is the
+                            // label itself, which we can't alter, so, error:
+                            Err(CompileError(0, 0, format!("Invalid lvalue {}", name)))
+                        }
+                        Variable::IndirectLabel(label) => {
+                            // Indirect labels are variables, the label is where the data is stored,
+                            // so we push that label so we can store stuff there
+                            let label = label.clone();
+                            sig.emit_arg("push", label);
+                            Ok(())
+                        }
+                        Variable::Local(offset) => {
+                            let offset = *offset;
+                            sig.emit_arg("loadw", "frame");
+                            if offset > 0 {
+                                sig.emit_arg("add", offset);
+                            }
+                            Ok(())
+                        }
                     }
-                    Ok(())
+                } else {
+                    Err(CompileError(0, 0, format!("Unknown name {}", name)))
                 }
             }
-        } else {
-            Err(CompileError(0, 0, format!("Unknown name {}", self.name)))
+            Self::Expr(BoxExpr(expr)) => {
+                // Just compile the expression and that's the address to write to
+                (*expr).process(state, Some(sig))
+            }
         }
     }
 }
@@ -748,4 +756,28 @@ mod test {
             .join("\n")
         )
     }
+
+    #[test]
+    fn test_derefs() {
+        let mut state = State::default();
+        parse("fn blah() { var x = 3; *1000 = *x; }")
+            .unwrap()
+            .process(&mut state, None)
+            .expect("Failed to compile");
+        let body = body_as_string(state.functions.get("blah").unwrap());
+        assert_eq!(
+            body,
+            vec![
+                "push 3",
+                "loadw frame",
+                "storew",      // the assignment for x
+                "loadw frame", // Now we're compiling *x, so load x's value, which is 3
+                "loadw", // Then load the value at 3
+                "push 1000", // Push the addr 1000, for the lvalue
+                "storew" // Store whatever's at 3 to 1000
+            ]
+                .join("\n")
+        )
+
+    }
 }

forge_core/src/forge_parser.rs

@@ -334,15 +334,20 @@ impl AstNode for Lvalue {
     const RULE: Rule = Rule::lvalue;
     fn from_pair(pair: Pair) -> Self {
         let mut pairs = pair.into_inner();
-        let name = String::from(pairs.next().unwrap().as_str());
-        let subscripts: Vec<_> = pairs
-            .map(|p| match p.as_rule() {
-                Rule::subscript => Suffix::Subscript(Expr::from_pair(p.first()).into()),
-                Rule::member => Suffix::Member(p.first_as_string()),
-                _ => unreachable!(),
-            })
-            .collect();
-        Self { name, subscripts }
+        let first = pairs.next().unwrap();
+        if first.as_rule() == Rule::expr {
+            Self::Expr(Expr::from_pair(first).into())
+        } else {
+            let name = String::from(first.as_str());
+            let subscripts: Vec<_> = pairs
+                .map(|p| match p.as_rule() {
+                    Rule::subscript => Suffix::Subscript(Expr::from_pair(p.first()).into()),
+                    Rule::member => Suffix::Member(p.first_as_string()),
+                    _ => unreachable!(),
+                })
+                .collect();
+            Self::Name(name, subscripts)
+        }
     }
 }
 
@@ -846,10 +851,7 @@ mod test {
         // Addresses
         assert_eq!(
             Expr::from_str("&foo.bar"),
-            Ok(Expr::Address(Lvalue {
-                name: "foo".into(),
-                subscripts: vec![Suffix::Member("bar".into())]
-            }))
+            Ok(Expr::Address(Lvalue::Name("foo".into(), vec![Suffix::Member("bar".into())])))
         );
 
         assert_eq!(
@@ -930,13 +932,18 @@ mod test {
         assert_eq!(
             Assignment::from_str("foo[45] = 7"),
             Ok(Assignment {
-                lvalue: Lvalue {
-                    name: String::from("foo"),
-                    subscripts: vec![Suffix::Subscript(45.into())]
-                },
+                lvalue: Lvalue::Name("foo".into(), vec![Suffix::Subscript(45.into())]),
                 rvalue: Rvalue::Expr(7.into()),
             })
         );
+
+        assert_eq!(
+            Assignment::from_str("*foo = 12"),
+            Ok(Assignment {
+                lvalue: Lvalue::Expr("foo".into()),
+                rvalue: Rvalue::Expr(12.into())
+            })
+        );
     }
 
     #[test]

forge_core/src/new.pest

@@ -20,7 +20,7 @@ string_inner = ${ !("\"" | "\\") ~ ANY | escape }
 string       = ${ "\"" ~ string_inner* ~ "\"" }
 
 assignment = { lvalue ~ "=" ~ rvalue }
-lvalue     = { name ~ (modifier)* }
+lvalue     = { (name ~ (modifier)*) | ("*" ~ expr) }
 rvalue     = { expr | string }
 
 add     = { "+" }