From ca979edd7ca3f79ef844f6f0efc90a6d8dbc3773 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Mon, 21 Nov 2022 15:14:18 +0100
Subject: [PATCH] Desugar variable access and assignment

---
 src/desugar.rs      |   1 +
 src/desugar/expr.rs |   6 +-
 src/desugar/var.rs  | 161 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 165 insertions(+), 3 deletions(-)
 create mode 100644 src/desugar/var.rs

diff --git a/src/desugar.rs b/src/desugar.rs
index c1037be..7402709 100644
--- a/src/desugar.rs
+++ b/src/desugar.rs
@@ -4,3 +4,4 @@ mod expr;
 mod field;
 mod lit;
 mod program;
+mod var;
diff --git a/src/desugar/expr.rs b/src/desugar/expr.rs
index 022592a..0c8e569 100644
--- a/src/desugar/expr.rs
+++ b/src/desugar/expr.rs
@@ -10,11 +10,11 @@ impl Expr {
 
             Self::Call(call) => call.desugar(),
             Self::Field(field) => field.desugar(),
+            Self::Var(var) => var.desugar(),
 
-            Self::Var(var) => (Self::Var(var), false), // TODO Implement
             Self::TableConstr(constr) => (Self::TableConstr(constr), false), // TODO Implement
-            Self::TableDestr(destr) => (Self::TableDestr(destr), false), // TODO Implement
-            Self::FuncDef(def) => (Self::FuncDef(def), false), // TODO Implement
+            Self::TableDestr(destr) => (Self::TableDestr(destr), false),     // TODO Implement
+            Self::FuncDef(def) => (Self::FuncDef(def), false),               // TODO Implement
 
             Self::Paren {
                 s0,
diff --git a/src/desugar/var.rs b/src/desugar/var.rs
new file mode 100644
index 0000000..887d115
--- /dev/null
+++ b/src/desugar/var.rs
@@ -0,0 +1,161 @@
+use crate::ast::{
+    Call, Expr, Field, Line, Lit, Separated, Space, StringLit, StringLitElem, TableConstr,
+    TableConstrElem, TableLitElem, Var,
+};
+use crate::builtin::Builtin;
+use crate::span::HasSpan;
+
+impl Var {
+    pub fn desugar(self) -> (Expr, bool) {
+        match self {
+            Self::Access {
+                s0,
+                index,
+                s1,
+                span,
+            } => {
+                // `[ s0 index s1 ]`
+                // -> `'scope()[ s0 index s1 ]`
+                let scope = Expr::Call(Call::NoArg {
+                    expr: Box::new(Expr::Lit(Lit::Builtin(Builtin::Scope, span))),
+                    s0: Space::empty(span),
+                    s1: Space::empty(span),
+                    span,
+                });
+                let new = Expr::Field(Field::Access {
+                    expr: Box::new(scope),
+                    s0: Space::empty(span),
+                    s1: s0,
+                    index,
+                    s2: s1,
+                    span,
+                });
+                (new, true)
+            }
+
+            Self::Assign {
+                local: None,
+                s0,
+                index,
+                s1,
+                s2,
+                s3,
+                value,
+                span,
+            } => {
+                // `[ s0 index s1 ] s2 = s3 value`
+                // -> `'scope()[ s0 index s1 ] s2 = s3 value`
+                let scope = Expr::Call(Call::NoArg {
+                    expr: Box::new(Expr::Lit(Lit::Builtin(Builtin::Scope, span))),
+                    s0: Space::empty(span),
+                    s1: Space::empty(span),
+                    span,
+                });
+                let new = Expr::Field(Field::Assign {
+                    expr: Box::new(scope),
+                    s0: Space::empty(span),
+                    s1: s0,
+                    index,
+                    s2: s1,
+                    s3: s2,
+                    s4: s3,
+                    value,
+                    span,
+                });
+                (new, true)
+            }
+
+            Self::Assign {
+                local: Some(local),
+                s0,
+                index,
+                s1,
+                s2,
+                s3,
+                value,
+                span,
+            } => {
+                // `local [ s0 index s1 ] s2 = s3 value`
+                // --> `'setraw { 'scope(), local s0 index s1, s2 s3 value }`
+                let scope = Expr::Call(Call::NoArg {
+                    expr: Box::new(Expr::Lit(Lit::Builtin(Builtin::Scope, span))),
+                    s0: Space::empty(span),
+                    s1: Space::empty(span),
+                    span,
+                });
+                let elems = Separated::NonEmpty {
+                    first_elem: TableConstrElem::Lit(TableLitElem::Positional(Box::new(scope))),
+                    last_elems: vec![
+                        (
+                            (Space::empty(span), local.then_line(Line::Empty).then(s0)),
+                            TableConstrElem::Lit(TableLitElem::Positional(index)),
+                        ),
+                        (
+                            (s1, s2.then_line(Line::Empty).then(s3)),
+                            TableConstrElem::Lit(TableLitElem::Positional(value)),
+                        ),
+                    ],
+                    trailing: None,
+                    span,
+                };
+                let constr = TableConstr {
+                    s0: Space::empty(span),
+                    elems,
+                    s1: Space::empty(span),
+                    span,
+                };
+                let new = Expr::Call(Call::Constr {
+                    expr: Box::new(Expr::Lit(Lit::Builtin(Builtin::SetRaw, span))),
+                    s0: Space::empty(span),
+                    constr,
+                    span,
+                });
+                (new, true)
+            }
+
+            Self::AccessIdent(name) => {
+                // `name`
+                // -> `[ name_str ]`
+                let span = name.span();
+                let name_str = Expr::Lit(Lit::String(StringLit {
+                    elems: vec![StringLitElem::Plain(name.name)],
+                    span,
+                }));
+                let new = Expr::Var(Self::Access {
+                    s0: Space::empty(span),
+                    index: Box::new(name_str),
+                    s1: Space::empty(span),
+                    span,
+                });
+                (new, true)
+            }
+
+            Self::AssignIdent {
+                local,
+                name,
+                s0,
+                s1,
+                value,
+                span,
+            } => {
+                // `local name s0 = s1 value`
+                // -> `local [ name_str ] s0 = s1 value`
+                let name_str = Expr::Lit(Lit::String(StringLit {
+                    elems: vec![StringLitElem::Plain(name.name)],
+                    span: name.span,
+                }));
+                let new = Expr::Var(Self::Assign {
+                    local,
+                    s0: Space::empty(span),
+                    index: Box::new(name_str),
+                    s1: Space::empty(span),
+                    s2: s0,
+                    s3: s1,
+                    value,
+                    span,
+                });
+                (new, true)
+            }
+        }
+    }
+}