Statements

src/parser/ast.rs

@@ -1,5 +1,11 @@
 use serde::Serialize;
 
+#[derive(Debug, Clone, Serialize)]
+pub struct ParamList(pub Vec<(String, TypeExpr)>);
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Block(pub Vec<Statement>);
+
 #[derive(Debug, Clone, Serialize)]
 #[serde(tag = "type", content = "value")]
 pub enum TypeExpr {
@@ -24,10 +30,55 @@ pub enum TopLevel {
     },
 }
 
+#[derive(Debug, Clone, Serialize)]
+#[serde(tag = "type", content = "value")]
+pub enum Postfix {
+    FieldAccess(String),
+    FunctionCall(Vec<Expression>),
+}
+
 #[derive(Debug, Clone, Serialize)]
 #[serde(tag = "type", content = "value")]
 pub enum Statement {
+    // expr;
     Expression(Expression),
+
+    // { ... }
+    Block(Block),
+
+    // let/const/var x = ...
+    VarDecl {
+        kind: VarKind,
+        name: String,
+        init: Option<Expression>,
+    },
+
+    // if (...) stmt else stmt
+    If {
+        condition: Expression,
+        then_branch: Box<Statement>,
+        else_branch: Option<Box<Statement>>,
+    },
+
+    // while (...) stmt
+    While {
+        condition: Expression,
+        body: Box<Statement>,
+    },
+
+    // for (...) stmt
+    For {
+        init: Option<ForInit>,
+        condition: Option<Expression>,
+        update: Option<Expression>,
+        body: Box<Statement>,
+    },
+
+    // return expr?;
+    Return(Option<Expression>),
+
+    Break,
+    Continue,
 }
 
 #[derive(Debug, Clone, Serialize)]
@@ -45,14 +96,18 @@ pub enum Expression {
 }
 
 #[derive(Debug, Clone, Serialize)]
-#[serde(tag = "type", content = "value")]
-pub enum Postfix {
-    FieldAccess(String),
-    FunctionCall(Vec<Expression>),
+pub enum VarKind {
+    Let,
+    Const,
+    Var,
 }
 
 #[derive(Debug, Clone, Serialize)]
-pub struct ParamList(pub Vec<(String, TypeExpr)>);
-
-#[derive(Debug, Clone, Serialize)]
-pub struct Block(pub Vec<Statement>);
+pub enum ForInit {
+    VarDecl {
+        kind: VarKind,
+        name: String,
+        init: Option<Expression>,
+    },
+    Expr(Expression),
+}

src/parser/grammar.pest

@@ -36,10 +36,56 @@ block = { "{" ~ statement_list ~ "}" }
 
 statement_list = { statement* }
 
-statement = _{ expr_stmt }
+statement = _{
+      expr_stmt
+    | var_decl
+    | if_stmt
+    | while_stmt
+    | for_stmt
+    | return_stmt
+    | break_stmt
+    | continue_stmt
+    | block
+}
+
+// --- basic statements ---
 
 expr_stmt = { expr ~ ";" }
 
+return_stmt = { "return" ~ expr? ~ ";" }
+
+break_stmt = { "break" ~ ";" }
+
+continue_stmt = { "continue" ~ ";" }
+
+// --- variable declarations ---
+
+var_decl = {
+    ("let" | "const" | "var") ~ identifier ~ ("=" ~ expr)? ~ ";"
+}
+
+// --- control flow ---
+
+if_stmt = {
+    "if" ~ "(" ~ expr ~ ")" ~ statement ~ ("else" ~ statement)?
+}
+
+while_stmt = {
+    "while" ~ "(" ~ expr ~ ")" ~ statement
+}
+
+for_stmt = {
+    "for" ~ "(" ~ (var_decl_no_semicolon | expr_stmt | ";")
+           ~ expr? ~ ";"
+           ~ expr? ~ ")"
+           ~ statement
+}
+
+// helper (same as var_decl but no trailing ;)
+var_decl_no_semicolon = {
+    ("let" | "const" | "var") ~ identifier ~ ("=" ~ expr)?
+}
+
 // ================= EXPRESSIONS =================
 type_expr = { identifier }
 

src/parser/mod.rs

@@ -154,10 +154,118 @@ impl Statement {
                 let inner = pair.into_inner().next().unwrap();
                 Statement::from_pair(inner)
             }
+
             Rule::expr_stmt => {
                 let expr_pair = pair.into_inner().next().unwrap();
                 Statement::Expression(Expression::from_pair(expr_pair))
             }
+
+            Rule::block => Statement::Block(Block::from_pair(pair.into_inner().next().unwrap())),
+
+            Rule::var_decl => {
+                let mut inner = pair.into_inner();
+
+                let kind_pair = inner.next().unwrap(); // let/const/var
+                let name_pair = inner.next().unwrap(); // identifier
+
+                let init = inner.next().map(|expr_pair| {
+                    // expects "=" expr
+                    Expression::from_pair(expr_pair.into_inner().next().unwrap())
+                });
+
+                let kind = match kind_pair.as_str() {
+                    "let" => VarKind::Let,
+                    "const" => VarKind::Const,
+                    "var" => VarKind::Var,
+                    _ => unreachable!(),
+                };
+
+                Statement::VarDecl {
+                    kind,
+                    name: name_pair.as_str().to_string(),
+                    init,
+                }
+            }
+
+            Rule::return_stmt => {
+                let mut inner = pair.into_inner();
+
+                let expr = inner.next().map(Expression::from_pair);
+
+                Statement::Return(expr)
+            }
+
+            Rule::break_stmt => Statement::Break,
+
+            Rule::continue_stmt => Statement::Continue,
+
+            Rule::if_stmt => {
+                let mut inner = pair.into_inner();
+
+                let condition = Expression::from_pair(inner.next().unwrap());
+                let then_branch = Statement::from_pair(inner.next().unwrap());
+
+                let else_branch = inner.next().map(Statement::from_pair);
+
+                Statement::If {
+                    condition,
+                    then_branch: Box::new(then_branch),
+                    else_branch: else_branch.map(Box::new),
+                }
+            }
+
+            Rule::while_stmt => {
+                let mut inner = pair.into_inner();
+
+                let condition = Expression::from_pair(inner.next().unwrap());
+                let body = Statement::from_pair(inner.next().unwrap());
+
+                Statement::While {
+                    condition,
+                    body: Box::new(body),
+                }
+            }
+
+            Rule::for_stmt => {
+                let mut inner = pair.into_inner();
+
+                let init = inner.next().map(|p| match p.as_rule() {
+                    Rule::var_decl_no_semicolon => {
+                        let mut it = p.into_inner();
+
+                        let kind = match it.next().unwrap().as_str() {
+                            "let" => VarKind::Let,
+                            "const" => VarKind::Const,
+                            "var" => VarKind::Var,
+                            _ => unreachable!(),
+                        };
+
+                        let name = it.next().unwrap().as_str().to_string();
+                        let init_expr = it
+                            .next()
+                            .map(|e| Expression::from_pair(e.into_inner().next().unwrap()));
+
+                        ForInit::VarDecl {
+                            kind,
+                            name,
+                            init: init_expr,
+                        }
+                    }
+                    _ => ForInit::Expr(Expression::from_pair(p)),
+                });
+
+                let condition = inner.next().map(Expression::from_pair);
+                let update = inner.next().map(Expression::from_pair);
+                let body = Statement::from_pair(inner.next().unwrap());
+
+                Statement::For {
+                    init,
+                    condition,
+                    update,
+                    body: Box::new(body),
+                }
+            }
+
             _ => unimplemented!(
                 "Statement parsing not implemented yet: {:?}",
                 pair.as_rule()