Merge pull request 'try-catch' (#3) from try-catch into vm-bytecode

Reviewed-on: #3

aster-core/src/analysis.rs

@@ -102,6 +102,19 @@ fn collect_stmt(stmt: &Stmt, symbols: &mut Vec<Symbol>) {
             collect_expr(expr, symbols);
         }
         Stmt::Return(None) | Stmt::Break | Stmt::Continue => {}
+        Stmt::Try { body, catch_var, catch_body, finally_body } => {
+            collect_stmts(body, symbols);
+            if let Some(var) = catch_var {
+                symbols.push(Symbol { name: var.clone(), kind: SymbolKind::Variable });
+            }
+            if let Some(cb) = catch_body {
+                collect_stmts(cb, symbols);
+            }
+            if let Some(fb) = finally_body {
+                collect_stmts(fb, symbols);
+            }
+        }
+        Stmt::Throw(expr) => collect_expr(expr, symbols),
     }
 }
 

aster-core/src/ast/stmt.rs

@@ -58,4 +58,15 @@ pub enum Stmt {
 
     /// continue
     Continue,
+
+    /// try { body } catch (e) { catch_body } finally { finally_body }
+    Try {
+        body: Vec<Stmt>,
+        catch_var: Option<String>,
+        catch_body: Option<Vec<Stmt>>,
+        finally_body: Option<Vec<Stmt>>,
+    },
+
+    /// throw expr;
+    Throw(Expr),
 }

aster-core/src/lexer/lexer.rs

@@ -360,6 +360,10 @@ impl Lexer {
             "true" => TokenKind::True,
             "false" => TokenKind::False,
             "nil" => TokenKind::Nil,
+            "try" => TokenKind::Try,
+            "catch" => TokenKind::Catch,
+            "finally" => TokenKind::Finally,
+            "throw" => TokenKind::Throw,
             _ => TokenKind::Identifier(s),
         };
 

aster-core/src/lexer/token.rs

@@ -39,6 +39,10 @@ pub enum TokenKind {
     True,
     False,
     Nil,
+    Try,
+    Catch,
+    Finally,
+    Throw,
 
     EOF,
 }

aster-core/src/parser/parser.rs

@@ -54,6 +54,10 @@ impl Parser {
             self.continue_statement()
         } else if self.match_kind(&[TokenKind::Return]) {
             self.return_statement()
+        } else if self.match_kind(&[TokenKind::Try]) {
+            self.try_statement()
+        } else if self.match_kind(&[TokenKind::Throw]) {
+            self.throw_statement()
         } else if self.match_kind(&[TokenKind::LeftBrace]) {
             Ok(Stmt::Block(self.block()?))
         } else {
@@ -201,6 +205,39 @@ impl Parser {
         Ok(Stmt::Return(value))
     }
 
+    fn try_statement(&mut self) -> Result<Stmt, RuntimeError> {
+        self.consume(TokenKind::LeftBrace, "Expected '{' after 'try'.")?;
+        let body = self.block()?;
+
+        let mut catch_var = None;
+        let mut catch_body = None;
+        if self.match_kind(&[TokenKind::Catch]) {
+            self.consume(TokenKind::LeftParen, "Expected '(' after 'catch'.")?;
+            catch_var = Some(self.consume_ident("Expected exception variable.")?);
+            self.consume(TokenKind::RightParen, "Expected ')' after catch variable.")?;
+            self.consume(TokenKind::LeftBrace, "Expected '{' before catch body.")?;
+            catch_body = Some(self.block()?);
+        }
+
+        let mut finally_body = None;
+        if self.match_kind(&[TokenKind::Finally]) {
+            self.consume(TokenKind::LeftBrace, "Expected '{' after 'finally'.")?;
+            finally_body = Some(self.block()?);
+        }
+
+        if catch_var.is_none() && finally_body.is_none() {
+            return Err(RuntimeError::parse("Expected 'catch' or 'finally' after 'try'.", self.peek().clone()));
+        }
+
+        Ok(Stmt::Try { body, catch_var, catch_body, finally_body })
+    }
+
+    fn throw_statement(&mut self) -> Result<Stmt, RuntimeError> {
+        let expr = self.expression()?;
+        self.match_kind(&[TokenKind::Semicolon]); // 分号可选
+        Ok(Stmt::Throw(expr))
+    }
+
     fn block(&mut self) -> Result<Vec<Stmt>, RuntimeError> {
         let mut statements = Vec::new();
 
@@ -616,7 +653,9 @@ impl Parser {
                 | TokenKind::For
                 | TokenKind::Return
                 | TokenKind::Break
-                | TokenKind::Continue => return,
+                | TokenKind::Continue
+                | TokenKind::Try
+                | TokenKind::Throw => return,
                 _ => {
                     self.advance();
                 }

aster-core/src/runtime/mod.rs

@@ -26,6 +26,17 @@ pub struct FunctionProto {
     pub upvalue_count: u8,
     pub upvalues: Vec<(bool, u8)>,         // (is_local, index)
     pub lines: Vec<(usize, usize)>,         // (bytecode_offset, source_line)
+    pub exception_handlers: Vec<ExceptionHandler>,
+}
+
+/// Exception handler entry: defines a try-catch-finally region.
+#[derive(Debug, Clone)]
+pub struct ExceptionHandler {
+    pub try_start: usize,    // inclusive
+    pub try_end: usize,      // exclusive
+    pub catch_ip: usize,     // catch handler IP (0 if no catch clause)
+    pub catch_slot: u8,      // local slot for catch variable (0 if no catch)
+    pub finally_ip: usize,   // finally rethrow entry (0 if no finally)
 }
 
 impl FunctionProto {
@@ -39,6 +50,7 @@ impl FunctionProto {
             upvalue_count: 0,
             upvalues: Vec::new(),
             lines: Vec::new(),
+            exception_handlers: Vec::new(),
         }
     }
 

aster-core/src/vm/compiler.rs

@@ -7,7 +7,7 @@
 use crate::ast::*;
 use crate::ast::expr::{Literal, UnaryOp, BinaryOp, LogicalOp, AssignOp};
 use crate::error::RuntimeError;
-use crate::runtime::{Value, FunctionProto};
+use crate::runtime::{Value, FunctionProto, ExceptionHandler};
 use super::opcode::*;
 
 use std::rc::Rc;
@@ -139,6 +139,12 @@ impl Compiler {
             Stmt::Continue => {
                 self.compile_continue()?;
             }
+            Stmt::Try { body, catch_var, catch_body, finally_body } => {
+                self.compile_try(body, catch_var.as_deref(), catch_body.as_ref(), finally_body.as_ref())?;
+            }
+            Stmt::Throw(expr) => {
+                self.compile_throw(expr)?;
+            }
         }
         Ok(())
     }
@@ -375,6 +381,87 @@ impl Compiler {
         Ok(())
     }
 
+    fn compile_throw(&mut self, expr: &Expr) -> Result<(), RuntimeError> {
+        self.compile_expr(expr)?;
+        self.emit_op(OpCode::Throw);
+        Ok(())
+    }
+
+    fn compile_try(
+        &mut self,
+        body: &[Stmt],
+        catch_var: Option<&str>,
+        catch_body: Option<&Vec<Stmt>>,
+        finally_body: Option<&Vec<Stmt>>,
+    ) -> Result<(), RuntimeError> {
+        let try_start = self.function.code.len();
+
+        // Compile try body
+        self.begin_scope();
+        self.compile_stmts(body)?;
+        self.end_scope();
+        let try_end = self.function.code.len();
+
+        // ── Normal path: jump past catch to finally (or end) ──
+        let skip_catch = self.emit_jump(OpCode::Jump);
+
+        // ── Catch handler (entry via unwind) ──
+        let (catch_ip, catch_slot) = if let (Some(var), Some(cb)) = (catch_var, catch_body) {
+            let ip = self.function.code.len();
+            self.begin_scope();
+            let slot = self.locals.len() as u8;
+            self.locals.push(Local {
+                name: var.to_string(),
+                depth: self.scope_depth,
+                is_captured: false,
+                is_const: false,
+            });
+            // VM pushes exception value before jumping here; StoreLocal peeks it
+            emit_u8(&mut self.function.code, OpCode::StoreLocal, slot);
+            self.compile_stmts(cb)?;
+            self.end_scope();
+            (ip, slot)
+        } else {
+            (0, 0)
+        };
+        self.patch_jump(skip_catch);
+
+        // ── Finally: inline for success paths (try/catch fall through here) ──
+        let finally_block_ip = if let Some(fb) = finally_body {
+            let ip = self.function.code.len();
+            self.begin_scope();
+            self.compile_stmts(fb)?;
+            self.end_scope();
+            let done_jump = self.emit_jump(OpCode::Jump);
+
+            // ── Finally rethrow entry (for exception path) ──
+            let rethrow_ip = self.function.code.len();
+            // Duplicate finally body for exception path
+            self.begin_scope();
+            self.compile_stmts(fb)?;
+            self.end_scope();
+            self.emit_op(OpCode::Throw); // re-throw after finally
+
+            self.patch_jump(done_jump);
+            (ip, rethrow_ip)
+        } else {
+            (0, 0)
+        };
+
+        let (_, rethrow_ip) = finally_block_ip;
+
+        // Register exception handler
+        self.function.exception_handlers.push(ExceptionHandler {
+            try_start,
+            try_end,
+            catch_ip,
+            catch_slot,
+            finally_ip: rethrow_ip,
+        });
+
+        Ok(())
+    }
+
     // ========================================================================
     // Expression compilation
     // ========================================================================

aster-core/src/vm/opcode.rs

@@ -80,12 +80,13 @@ pub enum OpCode {
     CompoundAssignIndex = 41,   // operand: u8 compound-op tag
     CompoundAssignUpvalue = 44, // operand: u8 upvalue idx + u8 compound-op tag
     CompoundAssignGlobal = 45,  // operand: u16 name idx + u8 compound-op tag
+    Throw = 46,                 // pops exception value, begins stack unwind
 }
 
 impl OpCode {
     pub fn from_u8(byte: u8) -> Option<Self> {
         match byte {
-            0..=41 | 44..=45 => Some(unsafe { std::mem::transmute::<u8, OpCode>(byte) }),
+            0..=41 | 44..=46 => Some(unsafe { std::mem::transmute::<u8, OpCode>(byte) }),
             42 => Some(OpCode::LoadUpvalue),
             43 => Some(OpCode::StoreUpvalue),
             _ => None,
@@ -93,7 +94,7 @@ impl OpCode {
     }
 
     /// Total number of distinct opcodes
-    pub const COUNT: usize = 46;
+    pub const COUNT: usize = 47;
 }
 
 /// Compound assignment operator tags (used as operand byte after

aster-core/src/vm/tests.rs

@@ -1737,3 +1737,305 @@ fn eval_require_empty_module() {
         v => panic!("Expected Object, got {:?}", v),
     }
 }
+
+// =========================================================================
+// Exception handling: throw
+// =========================================================================
+
+#[test]
+fn eval_throw_caught() {
+    let vm = run("
+        let result = 'none';
+        try {
+            throw 'caught!';
+        } catch (e) {
+            result = e;
+        }
+    ");
+    match get_var(&vm, "result") {
+        Value::String(s) => assert_eq!(s, "caught!"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_throw_preserves_value_type() {
+    let vm = run("
+        let msg = '';
+        let code = 0;
+        try { throw 'error'; } catch (e) { msg = e; }
+        try { throw 42; } catch (e) { code = e; }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert_eq!(s, "error"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    assert_num(&get_var(&vm, "code"), 42.0);
+}
+
+#[test]
+fn eval_throw_caught_correct_handler() {
+    let vm = run("
+        let outer = 'none';
+        let inner = 'none';
+        try {
+            try {
+                throw 'inner';
+            } catch (e) {
+                inner = e;
+            }
+        } catch (e) {
+            outer = e;
+        }
+    ");
+    match get_var(&vm, "inner") {
+        Value::String(s) => assert_eq!(s, "inner"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    match get_var(&vm, "outer") {
+        Value::String(s) => assert_eq!(s, "none"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+// =========================================================================
+// Exception handling: runtime errors caught
+// =========================================================================
+
+#[test]
+fn eval_catch_division_by_zero() {
+    let vm = run("
+        let msg = 'none';
+        try {
+            let x = 1 / 0;
+        } catch (e) {
+            msg = e;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert!(s.contains("Division by zero") || s.contains("division"), "got: {}", s),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_catch_undefined_variable() {
+    let vm = run("
+        let msg = 'none';
+        try {
+            let x = no_such_var;
+        } catch (e) {
+            msg = e;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert!(s.contains("Undefined"), "got: {}", s),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_catch_index_out_of_bounds() {
+    let vm = run("
+        let msg = 'none';
+        try {
+            let x = [1, 2][99];
+        } catch (e) {
+            msg = e;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert!(s.contains("out of bounds"), "got: {}", s),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_catch_call_non_function() {
+    let vm = run("
+        let msg = 'none';
+        try {
+            42();
+        } catch (e) {
+            msg = e;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert!(s.contains("non-function"), "got: {}", s),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_no_error_runs_normally() {
+    let vm = run("
+        let result = 0;
+        try {
+            result = 42;
+        } catch (e) {
+            result = -1;
+        }
+    ");
+    assert_num(&get_var(&vm, "result"), 42.0);
+}
+
+// =========================================================================
+// Exception handling: finally
+// =========================================================================
+
+#[test]
+fn eval_finally_runs_on_success() {
+    let vm = run("
+        let flag = 0;
+        try {
+            flag = 1;
+        } finally {
+            flag = flag + 10;
+        }
+    ");
+    assert_num(&get_var(&vm, "flag"), 11.0);
+}
+
+#[test]
+fn eval_finally_runs_on_throw() {
+    let vm = run("
+        let flag = 0;
+        let msg = 'none';
+        try {
+            throw 'oops';
+        } catch (e) {
+            msg = e;
+        } finally {
+            flag = flag + 10;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert_eq!(s, "oops"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    assert_num(&get_var(&vm, "flag"), 10.0);
+}
+
+#[test]
+fn eval_finally_runs_on_runtime_error() {
+    let vm = run("
+        let flag = 0;
+        let msg = 'none';
+        try {
+            let x = 1 / 0;
+        } catch (e) {
+            msg = 'caught';
+        } finally {
+            flag = 1;
+        }
+    ");
+    match get_var(&vm, "msg") {
+        Value::String(s) => assert_eq!(s, "caught"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    assert_num(&get_var(&vm, "flag"), 1.0);
+}
+
+#[test]
+fn eval_finally_without_catch() {
+    // try-finally without catch: finally runs, then rethrows
+    let result = std::panic::catch_unwind(|| {
+        run("
+            let flag = 0;
+            try {
+                throw 'boom';
+            } finally {
+                flag = 1;
+            }
+        ");
+    });
+    assert!(result.is_err(), "Expected uncaught exception");
+}
+
+#[test]
+fn eval_nested_try_catch() {
+    let vm = run("
+        let outer = 'none';
+        let inner = 'none';
+        try {
+            try {
+                throw 'inner_error';
+            } catch (e) {
+                inner = e;
+            }
+        } catch (e) {
+            outer = e;
+        }
+    ");
+    match get_var(&vm, "inner") {
+        Value::String(s) => assert_eq!(s, "inner_error"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    match get_var(&vm, "outer") {
+        Value::String(s) => assert_eq!(s, "none"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_throw_in_catch_propagates() {
+    let vm = run("
+        let outer = 'none';
+        let inner = 'none';
+        try {
+            try {
+                throw 'first';
+            } catch (e) {
+                inner = e;
+                throw 'second';
+            }
+        } catch (e) {
+            outer = e;
+        }
+    ");
+    match get_var(&vm, "inner") {
+        Value::String(s) => assert_eq!(s, "first"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+    match get_var(&vm, "outer") {
+        Value::String(s) => assert_eq!(s, "second"),
+        v => panic!("Expected String, got {:?}", v),
+    }
+}
+
+#[test]
+fn eval_try_catch_in_function() {
+    let vm = run("
+        fn safe_div(a, b) {
+            try {
+                return a / b;
+            } catch (e) {
+                return -1;
+            }
+        }
+        let r1 = safe_div(10, 2);
+        let r2 = safe_div(10, 0);
+    ");
+    assert_num(&get_var(&vm, "r1"), 5.0);
+    assert_num(&get_var(&vm, "r2"), -1.0);
+}
+
+#[test]
+fn eval_finally_known_limitation_return() {
+    // Note: return/break/continue inside try-finally do NOT yet run finally
+    // (this is a known limitation). This test documents current behavior.
+    let vm = run("
+        let flag = 0;
+        fn test() {
+            try {
+                return 42;
+            } finally {
+                flag = 1;
+            }
+        }
+        let r = test();
+    ");
+    assert_num(&get_var(&vm, "r"), 42.0);
+    // flag stays 0 because finally doesn't run before return (known limitation)
+    assert_num(&get_var(&vm, "flag"), 0.0);
+}

aster-core/src/vm/vm.rs

@@ -4,7 +4,7 @@
 //! call frames. Implements the `Runtime` trait for native function support.
 
 use crate::error::RuntimeError;
-use crate::runtime::{Value, Runtime, FunctionProto, Closure, UpvalueObj};
+use crate::runtime::{Value, Runtime, FunctionProto, Closure, UpvalueObj, ExceptionHandler};
 use crate::lexer::Lexer;
 use crate::parser::Parser;
 use super::opcode::*;
@@ -109,8 +109,26 @@ impl Vm {
 
     fn execute_loop(&mut self) -> Result<(), RuntimeError> {
         loop {
+            match self.execute_one_step() {
+                Ok(true) => continue,  // more instructions to execute
+                Ok(false) => return Ok(()),  // VM finished
+                Err(runtime_err) => {
+                    // Try to handle as exception
+                    let exc = Value::String(runtime_err.to_string());
+                    self.unwind(exc)?; // Err if no handler found
+                    continue; // Handler found, continue executing
+                }
+            }
+        }
+    }
+
+    /// Execute a single bytecode instruction. Returns:
+    /// - Ok(true): continue the loop
+    /// - Ok(false): VM is done (frames empty)
+    /// - Err(...): runtime error to potentially catch
+    fn execute_one_step(&mut self) -> Result<bool, RuntimeError> {
         if self.frames.is_empty() {
-                return Ok(());
+            return Ok(false);
         }
 
         // Snapshot frame state (must drop borrow before mutating self)
@@ -122,12 +140,12 @@ impl Vm {
             let frame = self.frames.pop().unwrap();
             self.close_upvalues(frame.stack_base);
             if self.frames.is_empty() {
-                    return Ok(());
+                return Ok(false);
             }
             // Remove callee + args + function locals, push nil result
             self.stack.truncate(frame.stack_base.saturating_sub(1));
             self.stack.push(Value::Nil);
-                continue;
+            return Ok(true);
         }
 
         // Clone Rc<FunctionProto> to access code without holding self.frames borrow
@@ -445,7 +463,7 @@ impl Vm {
                     self.stack.truncate(frame.stack_base.saturating_sub(1));
                     self.stack.push(result);
                     if self.frames.is_empty() {
-                        return Ok(());
+                        return Ok(false);
                     }
                 }
                 OpCode::Closure => {
@@ -645,8 +663,16 @@ impl Vm {
                     self.stack.push(result);
                     self.advance_ip(SIZE_U16_PLUS1);
                 }
+                OpCode::Throw => {
+                    let exc = self.stack.pop().unwrap();
+                    self.unwind(exc)?;
+                    // unwind() returns Ok only if it found a handler and jumped there
+                    return Ok(true);
                 }
         }
+
+        // All ops (except Throw) fall through to here
+        Ok(true)
     }
 
     // ========================================================================
@@ -665,6 +691,63 @@ impl Vm {
         self.frame_mut().ip = target;
     }
 
+    // ========================================================================
+    // Exception handling (stack unwind)
+    // ========================================================================
+
+    /// Search for an exception handler covering the current IP.
+    /// Returns the handler and true if a handler was found.
+    fn find_handler(proto: &FunctionProto, ip: usize) -> Option<&ExceptionHandler> {
+        // Search in insertion order: innermost try is compiled (and registered) first,
+        // so forward iteration finds the innermost matching handler first.
+        proto.exception_handlers.iter().find(|h| ip >= h.try_start && ip < h.try_end)
+    }
+
+    /// Unwind the call stack to find an exception handler. On success,
+    /// the VM's IP is set to the handler and execution continues.
+    /// Returns Err if no handler is found (uncaught exception).
+    fn unwind(&mut self, exception: Value) -> Result<(), RuntimeError> {
+        loop {
+            if self.frames.is_empty() {
+                return Err(RuntimeError::RuntimeError {
+                    message: format!("Uncaught exception: {}", exception),
+                    token: None,
+                });
+            }
+
+            let ip = self.frames.last().unwrap().ip;
+            let proto = Rc::clone(&self.frames.last().unwrap().closure.proto);
+
+            if let Some(h) = Self::find_handler(&proto, ip) {
+                if h.finally_ip != 0 {
+                    if h.catch_ip != 0 {
+                        // Has catch: push exception, jump to catch.
+                        // Catch body falls through to inline finally.
+                        self.stack.push(exception);
+                        self.frame_mut().ip = h.catch_ip;
+                        return Ok(());
+                    } else {
+                        // No catch, only finally: push exception, jump to finally
+                        // rethrow entry. The finally body runs, then Throw.
+                        self.stack.push(exception);
+                        self.frame_mut().ip = h.finally_ip;
+                        return Ok(());
+                    }
+                } else if h.catch_ip != 0 {
+                    // Only catch, no finally
+                    self.stack.push(exception);
+                    self.frame_mut().ip = h.catch_ip;
+                    return Ok(());
+                }
+            }
+
+            // No handler — pop frame and continue in caller
+            let frame = self.frames.pop().unwrap();
+            self.close_upvalues(frame.stack_base);
+            self.stack.truncate(frame.stack_base.saturating_sub(1));
+        }
+    }
+
     // ========================================================================
     // Function calls
     // ========================================================================

aster-lsp/src/completion.rs

@@ -9,6 +9,7 @@ use lsp_types::{
 const KEYWORDS: &[&str] = &[
     "let", "const", "fn", "if", "else", "while", "for", "in",
     "break", "continue", "return", "true", "false", "nil",
+    "try", "catch", "finally", "throw",
 ];
 
 const BUILTINS: &[&str] = &[

aster-lsp/src/goto_def.rs

@@ -41,14 +41,8 @@ pub fn handle_goto_definition(
         let location = Location {
             uri: uri.clone(),
             range: Range {
-                start: Position {
+                start: Position { line: l, character: c },
-                    line: l,
+                end: Position { line: l, character: c + word.len() as u32 },
-                    character: c,
-                },
-                end: Position {
-                    line: l,
-                    character: c + word.len() as u32,
-                },
             },
         };
         let response: GotoDefinitionResponse = GotoDefinitionResponse::Scalar(location);

aster-lsp/src/server.rs

@@ -28,7 +28,17 @@ pub fn run() {
         text_document_sync: Some(TextDocumentSyncCapability::Kind(
             TextDocumentSyncKind::FULL,
         )),
-        completion_provider: Some(lsp_types::CompletionOptions::default()),
+        completion_provider: Some(lsp_types::CompletionOptions {
+            trigger_characters: Some(
+                (b'a'..=b'z').chain(b'A'..=b'Z')
+                    .map(|c| (c as char).to_string())
+                    .chain(std::iter::once(".".to_string()))
+                    .chain(std::iter::once("_".to_string()))
+                    .collect()
+            ),
+            resolve_provider: Some(false),
+            ..Default::default()
+        }),
         hover_provider: Some(lsp_types::HoverProviderCapability::Simple(true)),
         signature_help_provider: Some(lsp_types::SignatureHelpOptions::default()),
         definition_provider: Some(lsp_types::OneOf::Left(true)),

vscode-ext/syntaxes/aster.tmLanguage.json

@@ -84,7 +84,7 @@
             "patterns": [
                 {
                     "name": "keyword.control.aster",
-                    "match": "\\b(let|const|fn|if|else|while|for|in|break|continue|return)\\b"
+                    "match": "\\b(let|const|fn|if|else|while|for|in|break|continue|return|try|catch|finally|throw)\\b"
                 }
             ]
         },