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[dev.typeparams] cmd/compile: make type conversions by type parameters work
When doing a type conversion using a type param, delay the transformation to OCONV/OCONVNOP until stenciling, since the nodes created depend on the actual type. Re-enable the fact.go test. Change-Id: I3d5861aab3dd0e781d767f67435afaf951dfe451 Reviewed-on: https://go-review.googlesource.com/c/go/+/290752 Trust: Dan Scales <danscales@google.com> Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Dan Scales <danscales@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
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@ -84,6 +84,11 @@ func Call(pos src.XPos, typ *types.Type, fun ir.Node, args []ir.Node, dots bool)
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if fun.Op() == ir.OTYPE {
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// Actually a type conversion, not a function call.
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n := ir.NewCallExpr(pos, ir.OCALL, fun, args)
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if fun.Type().Kind() == types.TTYPEPARAM {
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// For type params, don't typecheck until we actually know
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// the type.
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return typed(typ, n)
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}
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return typecheck.Expr(n)
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}
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@ -174,30 +174,36 @@ func (subst *subster) node(n ir.Node) ir.Node {
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}
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ir.EditChildren(m, edit)
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// A method value/call via a type param will have been left as an
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// OXDOT. When we see this during stenciling, finish the
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// typechecking, now that we have the instantiated receiver type.
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// We need to do this now, since the access/selection to the
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// method for the real type is very different from the selection
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// for the type param.
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if x.Op() == ir.OXDOT {
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// Will transform to an OCALLPART
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// A method value/call via a type param will have been left as an
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// OXDOT. When we see this during stenciling, finish the
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// typechecking, now that we have the instantiated receiver type.
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// We need to do this now, since the access/selection to the
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// method for the real type is very different from the selection
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// for the type param.
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m.SetTypecheck(0)
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// m will transform to an OCALLPART
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typecheck.Expr(m)
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}
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if x.Op() == ir.OCALL {
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call := m.(*ir.CallExpr)
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if call.X.Op() != ir.OCALLPART {
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base.FatalfAt(call.Pos(), "Expecting OXDOT with CALL")
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if call.X.Op() == ir.OTYPE {
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// Do typechecking on a conversion, now that we
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// know the type argument.
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m.SetTypecheck(0)
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m = typecheck.Expr(m)
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} else if call.X.Op() == ir.OCALLPART {
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// Redo the typechecking, now that we know the method
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// value is being called.
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call.X.(*ir.SelectorExpr).SetOp(ir.OXDOT)
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call.X.SetTypecheck(0)
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call.X.SetType(nil)
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typecheck.Callee(call.X)
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m.SetTypecheck(0)
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typecheck.Call(m.(*ir.CallExpr))
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} else {
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base.FatalfAt(call.Pos(), "Expecting OCALLPART or OTYPE with CALL")
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}
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// Redo the typechecking, now that we know the method
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// value is being called
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call.X.(*ir.SelectorExpr).SetOp(ir.OXDOT)
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call.X.SetTypecheck(0)
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call.X.SetType(nil)
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typecheck.Callee(call.X)
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m.SetTypecheck(0)
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typecheck.Call(m.(*ir.CallExpr))
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}
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if x.Op() == ir.OCLOSURE {
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@ -8,20 +8,15 @@ package main
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import "fmt"
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// TODO Stenciling doesn't do the right thing for T(1) at the moment.
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func fact[T interface { type int, int64, float64 }](n T) T {
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// TODO remove this return in favor of the correct computation below
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return n
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// if n == T(1) {
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// return T(1)
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// }
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// return n * fact(n - T(1))
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if n == T(1) {
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return T(1)
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}
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return n * fact(n - T(1))
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}
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func main() {
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// TODO change this to 120 once we can compile the function body above
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const want = 5 // 120
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const want = 120
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if got := fact(5); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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