From 8b21acac9e88c4eb3206afe9589c79b623fa949c Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Mon, 21 Nov 2022 09:32:07 +0100
Subject: [PATCH] Add desugar command and desugar programs

---
 src/ast/basic.rs       |  9 ++++++++
 src/desugar.rs         |  1 +
 src/desugar/program.rs | 48 ++++++++++++++++++++++++++++++++++++++++++
 src/main.rs            | 42 +++++++++++++++++++++++++-----------
 src/pretty.rs          | 10 +++++++++
 src/span.rs            |  8 +++++++
 6 files changed, 106 insertions(+), 12 deletions(-)
 create mode 100644 src/desugar.rs
 create mode 100644 src/desugar/program.rs

diff --git a/src/ast/basic.rs b/src/ast/basic.rs
index 33562f2..49d867f 100644
--- a/src/ast/basic.rs
+++ b/src/ast/basic.rs
@@ -30,6 +30,15 @@ impl HasSpan for Space {
     }
 }
 
+impl Space {
+    pub fn empty(span: Span) -> Self {
+        Self {
+            lines: vec![],
+            span,
+        }
+    }
+}
+
 #[derive(Clone)]
 pub struct Ident {
     pub name: String,
diff --git a/src/desugar.rs b/src/desugar.rs
new file mode 100644
index 0000000..3847c62
--- /dev/null
+++ b/src/desugar.rs
@@ -0,0 +1 @@
+mod program;
diff --git a/src/desugar/program.rs b/src/desugar/program.rs
new file mode 100644
index 0000000..d97a6e0
--- /dev/null
+++ b/src/desugar/program.rs
@@ -0,0 +1,48 @@
+use crate::ast::{Expr, Lit, Program, Space, TableLit};
+use crate::span::HasSpan;
+
+impl Program {
+    pub fn desugar(self) -> (Self, bool) {
+        match self {
+            Self::Expr { s0, expr, s1, span } => {
+                let (expr, desugared) = (expr, false); // TODO Implement
+                (Self::Expr { s0, expr, s1, span }, desugared)
+            }
+
+            Self::Module {
+                s0,
+                s1,
+                elems,
+                s2,
+                span,
+            } => {
+                let (elems, desugared) = (elems, false); // TODO Implement
+                if desugared {
+                    let new = Self::Module {
+                        s0,
+                        s1,
+                        elems,
+                        s2,
+                        span,
+                    };
+                    (new, true)
+                } else {
+                    let elems_span = elems.span();
+                    let table = TableLit {
+                        s0: s1,
+                        elems,
+                        s1: Space::empty(elems_span.at_end()),
+                        span: elems_span,
+                    };
+                    let new = Self::Expr {
+                        s0,
+                        expr: Expr::Lit(Lit::Table(table)),
+                        s1: s2,
+                        span,
+                    };
+                    (new, true)
+                }
+            }
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 90cc696..0192a59 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,12 +17,13 @@
 use std::fs;
 use std::path::PathBuf;
 
-use ::pretty::{Pretty, RcAllocator};
+use anyhow::anyhow;
 use chumsky::Parser as _;
 use clap::Parser;
 
 mod ast;
 mod builtin;
+mod desugar;
 mod parser;
 mod pretty;
 mod span;
@@ -33,6 +34,7 @@ mod value;
 enum Command {
     Parse { file: PathBuf },
     Pretty { file: PathBuf },
+    Desugar { file: PathBuf },
 }
 
 #[derive(Parser)]
@@ -59,21 +61,37 @@ fn main() -> anyhow::Result<()> {
                 }
             }
         }
+
         Command::Pretty { file } => {
             let content = fs::read_to_string(&file)?;
             let stream = span::stream_from_str(&content);
-            match parser::parser().parse(stream) {
-                Ok(program) => {
-                    let mut out = vec![];
-                    program.pretty(&RcAllocator).render(100, &mut out)?;
-                    println!("{}", String::from_utf8(out)?);
-                }
-                Err(errs) => {
-                    eprintln!("Parsing failed");
-                    for err in errs {
-                        eprintln!("{err:?}");
-                    }
+            let program = parser::parser()
+                .parse(stream)
+                .map_err(|e| anyhow!("{e:?}"))?;
+
+            println!("{}", pretty::pretty_to_string(program, 100));
+        }
+
+        Command::Desugar { file } => {
+            let content = fs::read_to_string(&file)?;
+            let stream = span::stream_from_str(&content);
+            let mut program = parser::parser()
+                .parse(stream)
+                .map_err(|e| anyhow!("{e:?}"))?;
+
+            println!("{}", pretty::pretty_to_string(program.clone(), 100));
+
+            loop {
+                let (new_program, desugared) = program.desugar();
+                program = new_program;
+                if !desugared {
+                    break;
                 }
+
+                println!();
+                println!("================================================================================");
+                println!();
+                println!("{}", pretty::pretty_to_string(program.clone(), 100));
             }
         }
     }
diff --git a/src/pretty.rs b/src/pretty.rs
index e15aa53..20844f6 100644
--- a/src/pretty.rs
+++ b/src/pretty.rs
@@ -1,3 +1,5 @@
+use pretty::{Pretty, RcAllocator};
+
 mod basic;
 mod call;
 mod expr;
@@ -10,3 +12,11 @@ mod table_destr;
 mod var;
 
 const NEST_DEPTH: isize = 4;
+
+pub fn pretty_to_string<P: Pretty<'static, RcAllocator>>(p: P, width: usize) -> String {
+    let mut out = vec![];
+    p.pretty(&RcAllocator)
+        .render(width, &mut out)
+        .expect("p could not be rendered");
+    String::from_utf8(out).expect("p created non-utf8 string")
+}
diff --git a/src/span.rs b/src/span.rs
index 296f992..42cf32c 100644
--- a/src/span.rs
+++ b/src/span.rs
@@ -24,6 +24,14 @@ impl Span {
         let end = self.end.max(other.end);
         Self::new(start, end)
     }
+
+    pub fn at_start(self) -> Self {
+        Self::new(self.start, self.start)
+    }
+
+    pub fn at_end(self) -> Self {
+        Self::new(self.end, self.end)
+    }
 }
 
 impl fmt::Debug for Span {