v2: Type aliases cause nil dereference on --v3.1 flag

[rasibn]

Describe the bug

type RequestParam struct {
	Price PriceType `form:"price" json:"price"`
}

type PriceType string

// @Param request  query    RequestParam false "Query Params"

Screenshots

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x2b8 pc=0x1013d9fe8]

goroutine 1 [running]:
github.com/swaggo/swag/v2.(*Parser).parseStructFieldV3(0x140002ba000, 0x140011de6e0, 0x14001244b80)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:938 +0x3e8
github.com/swaggo/swag/v2.(*Parser).parseStructV3(0x140002ba000, 0x140011de6e0, 0x1400123e510)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:817 +0xac
github.com/swaggo/swag/v2.(*Parser).parseTypeExprV3(0x140002ba000, 0x101492f09?, {0x1016b6a08?, 0x1400122b398?}, 0x80?)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:740 +0x8bc
github.com/swaggo/swag/v2.(*Parser).ParseDefinitionV3(0x140002ba000, 0x14001ce9d10)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:660 +0x3a4
github.com/swaggo/swag/v2.(*Parser).getTypeSchemaV3(0x140002ba000, {0x140001eb04d, 0x12}, 0x140011dedc0, 0x0)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:611 +0xa7c
github.com/swaggo/swag/v2.(*OperationV3).ParseParamComment(0x14001e10c00, {0x140001eb030, 0x44}, 0x140011dedc0)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/operationv3.go:338 +0x92c
github.com/swaggo/swag/v2.(*OperationV3).ParseComment(0x14001e10c00, {0x140001eb020?, 0x1?}, 0x140011dedc0)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/operationv3.go:86 +0x180
github.com/swaggo/swag/v2.(*Parser).ParseRouterAPIInfoV3(0x140002ba000, 0x140012aacc0)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parserv3.go:456 +0x188
github.com/swaggo/swag/v2.(*PackagesDefinitions).RangeFiles(0x14000296cf0, 0x14001c9f598)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/packages.go:107 +0x27c
github.com/swaggo/swag/v2.(*Parser).ParseAPIMultiSearchDir(0x140002ba000, {0x140002abf50, 0x1, 0x0?}, {0x16eedb4bd, 0x13}, 0x64)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/parser.go:422 +0x328
github.com/swaggo/swag/v2/gen.(*Gen).Build(0x140002969f0, 0x1400028ac80)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/gen/gen.go:219 +0x5c8
main.initAction(0x140002a2000)
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/cmd/swag/main.go:207 +0x74c
github.com/urfave/cli/v2.(*Command).Run(0x14000294160, 0x140002a2000, {0x140001bc720, 0x6, 0x6})
        /Users/rasib.nadeem/go/pkg/mod/github.com/urfave/cli/[email protected]/command.go:274 +0x5e0
github.com/urfave/cli/v2.(*Command).Run(0x14000294580, 0x140001bfe40, {0x140001c4000, 0x7, 0x7})
        /Users/rasib.nadeem/go/pkg/mod/github.com/urfave/cli/[email protected]/command.go:267 +0x81c
github.com/urfave/cli/v2.(*App).RunContext(0x14000298000, {0x1016b7b98, 0x101ad3060}, {0x140001c4000, 0x7, 0x7})
        /Users/rasib.nadeem/go/pkg/mod/github.com/urfave/cli/[email protected]/app.go:332 +0x4f8
github.com/urfave/cli/v2.(*App).Run(...)
        /Users/rasib.nadeem/go/pkg/mod/github.com/urfave/cli/[email protected]/app.go:309
main.main()
        /Users/rasib.nadeem/go/pkg/mod/github.com/swaggo/swag/[email protected]/cmd/swag/main.go:285 +0x4e0

Your swag version
2.0.0

Your go version
go version go1.23.2 darwin/arm64

Desktop:

• OS: MacOS