parser: fix comptime if script mode (fix #6419) (#14578)

vlib/v/parser/parser.v

@@ -667,10 +667,15 @@ pub fn (mut p Parser) top_stmt() ast.Stmt {
 					return p.error('unexpected eof')
 				}
 				if_expr := p.if_expr(true)
-				return ast.ExprStmt{
+				cur_stmt := ast.ExprStmt{
 					expr: if_expr
 					pos: if_expr.pos
 				}
+				if comptime_if_expr_contains_top_stmt(if_expr) {
+					return cur_stmt
+				} else {
+					return p.other_stmts(cur_stmt)
+				}
 			}
 			.hash {
 				return p.hash()
@@ -688,6 +693,40 @@ pub fn (mut p Parser) top_stmt() ast.Stmt {
 				return p.comment_stmt()
 			}
 			else {
+				return p.other_stmts(ast.empty_stmt())
+			}
+		}
+		if p.should_abort {
+			break
+		}
+	}
+	// TODO remove dummy return statement
+	// the compiler complains if it's not there
+	return ast.empty_stmt()
+}
+
+fn comptime_if_expr_contains_top_stmt(if_expr ast.IfExpr) bool {
+	for branch in if_expr.branches {
+		for stmt in branch.stmts {
+			if stmt is ast.ExprStmt {
+				if stmt.expr is ast.IfExpr {
+					if !comptime_if_expr_contains_top_stmt(stmt.expr) {
+						return false
+					}
+				} else if stmt.expr is ast.CallExpr {
+					return false
+				}
+			} else if stmt is ast.AssignStmt {
+				return false
+			} else if stmt is ast.HashStmt {
+				return true
+			}
+		}
+	}
+	return true
+}
+
+fn (mut p Parser) other_stmts(cur_stmt ast.Stmt) ast.Stmt {
 	p.inside_fn = true
 	if p.pref.is_script && !p.pref.is_test {
 		p.script_mode = true
@@ -699,6 +738,9 @@ pub fn (mut p Parser) top_stmt() ast.Stmt {
 
 		p.open_scope()
 		mut stmts := []ast.Stmt{}
+		if cur_stmt != ast.empty_stmt() {
+			stmts << cur_stmt
+		}
 		for p.tok.kind != .eof {
 			stmts << p.stmt(false)
 		}
@@ -722,15 +764,6 @@ pub fn (mut p Parser) top_stmt() ast.Stmt {
 		return p.error('bad top level statement ' + p.tok.str())
 	}
 }
-		}
-		if p.should_abort {
-			break
-		}
-	}
-	// TODO remove dummy return statement
-	// the compiler complains if it's not there
-	return ast.empty_stmt()
-}
 
 // TODO [if vfmt]
 pub fn (mut p Parser) check_comment() ast.Comment {

vlib/v/tests/inout/comptime_if_script_mode.out

@@ -0,0 +1 @@
+others

vlib/v/tests/inout/comptime_if_script_mode.vv

@@ -0,0 +1,5 @@
+$if vinix {
+	println('vinix')
+} $else {
+	println('others')
+}