gotools/internal/typeparams/common.go

// UnpackIndexExpr extracts data from AST nodes that represent index
// expressions.
//
// For an ast.IndexExpr, the resulting indices slice will contain exactly one
// index expression. For an ast.IndexListExpr (go1.18+), it may have a variable
// number of index expressions.
//
// For nodes that don't represent index expressions, the first return value of
// UnpackIndexExpr will be nil.
func UnpackIndexExpr(n ast.Node) (x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) { … }

// PackIndexExpr returns an *ast.IndexExpr or *ast.IndexListExpr, depending on
// the cardinality of indices. Calling PackIndexExpr with len(indices) == 0
// will panic.
func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr { … }

// IsTypeParam reports whether t is a type parameter (or an alias of one).
func IsTypeParam(t types.Type) bool { … }

// GenericAssignableTo is a generalization of types.AssignableTo that
// implements the following rule for uninstantiated generic types:
//
// If V and T are generic named types, then V is considered assignable to T if,
// for every possible instantiation of V[A_1, ..., A_N], the instantiation
// T[A_1, ..., A_N] is valid and V[A_1, ..., A_N] implements T[A_1, ..., A_N].
//
// If T has structural constraints, they must be satisfied by V.
//
// For example, consider the following type declarations:
//
//	type Interface[T any] interface {
//		Accept(T)
//	}
//
//	type Container[T any] struct {
//		Element T
//	}
//
//	func (c Container[T]) Accept(t T) { c.Element = t }
//
// In this case, GenericAssignableTo reports that instantiations of Container
// are assignable to the corresponding instantiation of Interface.
func GenericAssignableTo(ctxt *types.Context, V, T types.Type) bool { … }