golang/go
cmd/compile: exponential compile-time with nested generic instantiations
Open
#78,342 opened on Mar 25, 2026
Repository metrics
- Stars
- (133,883 stars)
- PR merge metrics
- (PR metrics pending)
Description
Go version
go 1.26.1 / tip
Output of go env in your module/workspace:
GOARCH=arm64
What did you do?
case 1:
package p
type T[P any] struct { _,_,_,_,_,_,_,_ P }
type U T[T[T[T[T[T[T[T[T[T[int]]]]]]]]]]
case 2:
package p
type T[P any] struct { _,_,_,_,_,_,_,_ P }
type U T[T[T[T[T[T[T[T[T[T[T[int]]]]]]]]]]]
case 3:
package p
type T[P any] struct { _,_,_,_,_,_,_,_ P }
type U T[T[T[T[T[T[T[T[T[T[T[T[int]]]]]]]]]]]]
Run go build on the above and measure the time.
What did you see happen?
Very long compile time.
What did you expect to see?
Fast compilation.