From 193a10938660b65a96ddc010d34bba3040154590 Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Tue, 22 Sep 2020 00:03:45 +0200
Subject: [PATCH] move to new syntax, wip9

---
 examples/wip.rs     |  6 +++++-
 src/ast.rs          |  6 +++---
 src/check.rs        | 12 +++++++-----
 src/grammar.lalrpop | 15 ++++++++-------
 src/vm.rs           |  6 +++---
 5 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/examples/wip.rs b/examples/wip.rs
index 7756966..b744af2 100644
--- a/examples/wip.rs
+++ b/examples/wip.rs
@@ -1,5 +1,9 @@
 fn main() {
-    {}
+    {};
+
+    while true {}
+
+    if a {}
 
     let mut a = 5;
     a = 5;
diff --git a/src/ast.rs b/src/ast.rs
index a95542c..a0ca146 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -23,7 +23,7 @@ pub struct Path(pub Vec<Id>);
 #[derive(Debug, PartialEq, Clone)]
 pub struct Stmts {
     pub stmts: Vec<Stmt>,
-    pub ret: bool,
+    pub trailing_semi: bool,
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -221,11 +221,11 @@ impl Stmts {
 
             if i < len - 1 {
                 match s {
-                    Stmt::Block(_) | Stmt::If(_, _, _) => (),
+                    Stmt::Block(_) | Stmt::If(_, _, _) | Stmt::While(_, _) => (),
                     _ => write!(fmt, ";")?,
                 }
             } else {
-                if self.ret {
+                if self.trailing_semi {
                     write!(fmt, ";")?;
                 }
             }
diff --git a/src/check.rs b/src/check.rs
index 5baafbd..ddb772f 100644
--- a/src/check.rs
+++ b/src/check.rs
@@ -229,6 +229,7 @@ fn lexpr_type<'a>(
     }
 }
 
+// strip a "mut T" to a T
 fn strip_mut(t: Type) -> Type {
     match t {
         Type::Mut(t) => *t,
@@ -236,6 +237,7 @@ fn strip_mut(t: Type) -> Type {
     }
 }
 
+// determine if a type is declared recursively
 fn is_known(t: &Type) -> bool {
     use Type::*;
     match t {
@@ -371,8 +373,6 @@ pub fn check_stmts(
     type_env: &TypeEnv,
     var_env: &mut VarEnv,
 ) -> Result<Type, Error> {
-    use Stmt::*;
-
     var_env.push_empty_scope();
 
     let t = stmts
@@ -381,10 +381,10 @@ pub fn check_stmts(
         .try_fold(Type::Unit, |_, s| check_stmt(s, fn_env, type_env, var_env))?;
 
     var_env.pop_scope();
-    if !stmts.ret {
-        Ok(t.clone())
-    } else {
+    if stmts.trailing_semi {
         Ok(Type::Unit)
+    } else {
+        Ok(t.clone())
     }
 }
 
@@ -436,6 +436,8 @@ pub fn check(p: &Program) -> Result<(), Error> {
 
     for fd in p.fn_decls.iter() {
         trace!("check function\n{}", fd);
+        trace!("ast\n{:?}", fd);
+
         let mut var_env = VarEnv::new();
 
         // build a scope for the arguments
diff --git a/src/grammar.lalrpop b/src/grammar.lalrpop
index b978e1f..a6ce8a2 100644
--- a/src/grammar.lalrpop
+++ b/src/grammar.lalrpop
@@ -128,7 +128,7 @@ pub Block: Stmts = {
         };
         Stmts { 
             stmts, 
-            ret: match st { 
+            trailing_semi: match st { 
                 Some(_) => false, 
                 _ => true,
             } 
@@ -137,18 +137,19 @@ pub Block: Stmts = {
 }
 
 StmtSeq: Stmt = {
+    ";" => Stmt::Semi,
     <Stmt> ";" => <>,
-    StmtBlock => Stmt::Block(<>),
+    StmtBlock => <>,
 }
 
-StmtBlock: Stmts = {
-    "while" Expr Block => panic!(),
-    "if" Expr Block ("else" Block)? => panic!(),
-    Block,
+StmtBlock: Stmt = {
+    "while" <Expr> <Block> => Stmt::While(<>),
+    "if" <Expr> <Block> <("else" <Block>)?> => Stmt::If(<>),
+    Block => Stmt::Block(<>),
 }
 
 Stmt: Stmt = {
-    ";" => Stmt::Semi,
+    // ";" => Stmt::Semi,
     "let" <m: "mut"?> <id: Id> <t: (":" <Type>)?> <e: ("=" <Expr>)?>  => Stmt::Let(id, m.is_some(), t, e),
     <Expr> "=" <Expr> => Stmt::Assign(<>),
     <ExprNoBlock> => Stmt::Expr(<>),
diff --git a/src/vm.rs b/src/vm.rs
index 6c53c48..8e0aa62 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -290,11 +290,11 @@ fn eval_stmts(stmts: &Stmts, m: &mut Mem, fn_env: &FnEnv) -> Val {
         }
     }
     m.pop_scope();
-    if !stmts.ret {
+    if stmts.trailing_semi {
+        Val::Unit
+    } else {
         println!("statements with return value {:?}", stmt_val);
         stmt_val
-    } else {
-        Val::Unit
     }
 }
 
-- 
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