Fix lookaheadLambdaArg not to use parseExpr (#221)

* Fix lookaheadLambdaArg

* Remove unreachable code

parser.go

@@ -1596,13 +1596,34 @@ func (p *Parser) lookaheadLambdaArg() bool {
 		p.Lexer = lexer
 	}()
 
-	if p.Token.Kind != "(" && p.Token.Kind != token.TokenIdent {
+	switch p.Token.Kind {
+	case "(":
+		p.nextToken()
+		if p.Token.Kind != token.TokenIdent {
+			return false
+		}
+		p.nextToken()
+
+		for p.Token.Kind != ")" {
+			if p.Token.Kind != "," {
+				return false
+			}
+			p.nextToken()
+
+			if p.Token.Kind != token.TokenIdent {
+				return false
+			}
+			p.nextToken()
+		}
+		p.nextToken()
+
+		return p.Token.Kind == "->"
+	case token.TokenIdent:
+		p.nextToken()
+		return p.Token.Kind == "->"
+	default:
 		return false
 	}
-
-	// Note: all lambda patterns can be parsed as expr -> expr.
-	p.parseExpr()
-	return p.Token.Kind == "->"
 }
 
 func (p *Parser) parseLambdaArg() *ast.LambdaArg {

testdata/input/expr/array_functions_array_filter_one_arg_with_paren_lambda.sql

@@ -0,0 +1 @@
+ARRAY_FILTER([1 ,2, 3], (e) -> e > 1)

testdata/result/expr/array_functions_array_filter_one_arg_with_paren_lambda.sql.txt

@@ -0,0 +1,72 @@
+--- array_functions_array_filter_one_arg_with_paren_lambda.sql
+ARRAY_FILTER([1 ,2, 3], (e) -> e > 1)
+--- AST
+&ast.CallExpr{
+  Rparen: 36,
+  Func:   &ast.Ident{
+    NamePos: 0,
+    NameEnd: 12,
+    Name:    "ARRAY_FILTER",
+  },
+  Distinct: false,
+  Args:     []ast.Arg{
+    &ast.ExprArg{
+      Expr: &ast.ArrayLiteral{
+        Array:  -1,
+        Lbrack: 13,
+        Rbrack: 21,
+        Type:   nil,
+        Values: []ast.Expr{
+          &ast.IntLiteral{
+            ValuePos: 14,
+            ValueEnd: 15,
+            Base:     10,
+            Value:    "1",
+          },
+          &ast.IntLiteral{
+            ValuePos: 17,
+            ValueEnd: 18,
+            Base:     10,
+            Value:    "2",
+          },
+          &ast.IntLiteral{
+            ValuePos: 20,
+            ValueEnd: 21,
+            Base:     10,
+            Value:    "3",
+          },
+        },
+      },
+    },
+    &ast.LambdaArg{
+      Lparen: 24,
+      Args:   []*ast.Ident{
+        &ast.Ident{
+          NamePos: 25,
+          NameEnd: 26,
+          Name:    "e",
+        },
+      },
+      Expr: &ast.BinaryExpr{
+        Op:   ">",
+        Left: &ast.Ident{
+          NamePos: 31,
+          NameEnd: 32,
+          Name:    "e",
+        },
+        Right: &ast.IntLiteral{
+          ValuePos: 35,
+          ValueEnd: 36,
+          Base:     10,
+          Value:    "1",
+        },
+      },
+    },
+  },
+  NamedArgs:    []*ast.NamedArg(nil),
+  NullHandling: nil,
+  Having:       nil,
+}
+
+--- SQL
+ARRAY_FILTER([1, 2, 3], (e) -> e > 1)