diff --git a/.github/workflows/wa.yml b/.github/workflows/wa.yml
index 749fa2c908337a0205763a9e6fa2a13c186263e2..e43d03f41d48d4bbe1119ed4ec7bfec764ec6dcb 100644
--- a/.github/workflows/wa.yml
+++ b/.github/workflows/wa.yml
@@ -40,6 +40,7 @@ jobs:
       - run: go install
 
       - run: wa -h
+      - run: wa hello.wa
       - run: wa run _examples/hello
       - run: wa run _examples/prime
 
diff --git a/hello.wa b/hello.wa
index 2059fbb78362b4dfea9d7dfadd2249baf3d7c067..e29361ef715974d6575a56875579537cb6483c12 100644
--- a/hello.wa
+++ b/hello.wa
@@ -1,5 +1,11 @@
 # 版权 @2019 凹语言 作者。保留所有权利。
 
 fn main() {
-	println("老凹，吃了吗")
+	println("凹凹，吃了吗")
+	println(answer())
+}
+
+fn answer() => (x:int) {
+	x = 40 + 2
+	return
 }
diff --git a/internal/parser/parser.go b/internal/parser/parser.go
index 4df41c51b4b0659c0406055fe45b411f3f4e67d5..74bb09f597681a7814958001029d46b4ea44cb97 100644
--- a/internal/parser/parser.go
+++ b/internal/parser/parser.go
@@ -816,6 +816,7 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 	var list []ast.Expr
 	for {
 		list = append(list, p.parseVarType(ellipsisOk))
+		// 开头的 Ident 列表, 遇到非 ',' 时结束
 		if p.tok != token.COMMA {
 			break
 		}
@@ -825,11 +826,18 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 		}
 	}
 
+	// 解析可选的 ':'
+	var colonPos token.Pos
+	if p.tok == token.COLON {
+		colonPos = p.pos
+		p.next()
+	}
+
 	// analyze case
 	if typ := p.tryVarType(ellipsisOk); typ != nil {
 		// IdentifierList Type
 		idents := p.makeIdentList(list)
-		field := &ast.Field{Names: idents, Type: typ}
+		field := &ast.Field{Names: idents, ColonPos: colonPos, Type: typ}
 		params = append(params, field)
 		// Go spec: The scope of an identifier denoting a function
 		// parameter or result variable is the function body.
@@ -841,8 +849,12 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 		p.next()
 		for p.tok != token.RPAREN && p.tok != token.EOF {
 			idents := p.parseIdentList()
+			if p.tok == token.COLON {
+				colonPos = p.pos
+				p.next()
+			}
 			typ := p.parseVarType(ellipsisOk)
-			field := &ast.Field{Names: idents, Type: typ}
+			field := &ast.Field{Names: idents, ColonPos: colonPos, Type: typ}
 			params = append(params, field)
 			// Go spec: The scope of an identifier denoting a function
 			// parameter or result variable is the function body.
@@ -856,6 +868,12 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
 		return
 	}
 
+	// 缺少类型信息
+	if colonPos != token.NoPos {
+		p.errorExpected(p.pos, "type")
+		return
+	}
+
 	// Type { "," Type } (anonymous parameters)
 	params = make([]*ast.Field, len(list))
 	for i, typ := range list {