[dev.typeparams] cmd/compile/internal/types2: fix make with type parameter argument

For make with a type parameter argument, the structural type of
the type parameter's constraint determines what make is making.

Change-Id: I3b48f8ce3236b7624e0638b5f5be208c5915c987
Reviewed-on: https://go-review.googlesource.com/c/go/+/339899
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

3 files changed, 80 insertions, 112 deletions

diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index e9df605fd1..184cd027cb 100644
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -472,39 +472,21 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 			return
 		}
 
-		min, max := -1, 10
-		var valid func(t Type) bool
-		valid = func(t Type) bool {
-			var m int
-			switch t := under(t).(type) {
-			case *Slice:
-				m = 2
-			case *Map, *Chan:
-				m = 1
-			case *TypeParam:
-				return t.underIs(valid)
-			default:
-				return false
-			}
-			if m > min {
-				min = m
-			}
-			if m+1 < max {
-				max = m + 1
-			}
-			return true
-		}
-
-		if !valid(T) {
+		var min int // minimum number of arguments
+		switch optype(T).(type) {
+		case *Slice:
+			min = 2
+		case *Map, *Chan:
+			min = 1
+		case *top:
+			check.errorf(arg0, invalidArg+"cannot make %s; type parameter has no structural type", arg0)
+			return
+		default:
 			check.errorf(arg0, invalidArg+"cannot make %s; type must be slice, map, or channel", arg0)
 			return
 		}
-		if nargs < min || max < nargs {
-			if min == max {
-				check.errorf(call, "%v expects %d arguments; found %d", call, min, nargs)
-			} else {
-				check.errorf(call, "%v expects %d or %d arguments; found %d", call, min, max, nargs)
-			}
+		if nargs < min || min+1 < nargs {
+			check.errorf(call, invalidOp+"%v expects %d or %d arguments; found %d", call, min, min+1, nargs)
 			return
 		}
 
diff --git a/src/cmd/compile/internal/types2/testdata/check/builtins.go2 b/src/cmd/compile/internal/types2/testdata/check/builtins.go2
index 3881090603..0cfea93bf6 100644
--- a/src/cmd/compile/internal/types2/testdata/check/builtins.go2
+++ b/src/cmd/compile/internal/types2/testdata/check/builtins.go2
@@ -84,50 +84,41 @@ func _[T M4[K, V], K comparable, V any](m T) {
 
 // make
 
-type Bmc interface {
-	~map[rune]string | ~chan int
-}
-
-type Bms interface {
-	~map[string]int | ~[]int
-}
-
-type Bcs interface {
-	~chan bool | ~[]float64
-}
-
-type Bss interface {
-	~[]int | ~[]string
-}
-
-func _[T any]() {
-	_ = make(T /* ERROR invalid argument */)
-	_ = make(T /* ERROR invalid argument */, 10)
-	_ = make(T /* ERROR invalid argument */, 10, 20)
-}
-
-func _[T Bmc]() {
-	_ = make(T)
-	_ = make(T, 10)
-	_ = make /* ERROR expects 1 or 2 arguments */ (T, 10, 20)
-}
-
-func _[T Bms]() {
-	_ = make /* ERROR expects 2 arguments */ (T)
-	_ = make(T, 10)
-	_ = make /* ERROR expects 2 arguments */ (T, 10, 20)
-}
-
-func _[T Bcs]() {
-	_ = make /* ERROR expects 2 arguments */ (T)
-	_ = make(T, 10)
-	_ = make /* ERROR expects 2 arguments */ (T, 10, 20)
-}
-
-func _[T Bss]() {
-	_ = make /* ERROR expects 2 or 3 arguments */ (T)
-	_ = make(T, 10)
-	_ = make(T, 10, 20)
+func _[
+	S1 interface{ []int },
+	S2 interface{ []int | chan int },
+
+	M1 interface{ map[string]int },
+	M2 interface{ map[string]int | chan int },
+
+	C1 interface{ chan int },
+	C2 interface{ chan int | chan string },
+]() {
+	type S0 []int
+	_ = make([]int, 10)
+	_ = make(S0, 10)
+	_ = make(S1, 10)
+	_ = make /* ERROR not enough arguments */ ()
+	_ = make /* ERROR expects 2 or 3 arguments */ (S1)
+	_ = make(S1, 10, 20)
+	_ = make /* ERROR expects 2 or 3 arguments */ (S1, 10, 20, 30)
+	_ = make(S2 /* ERROR cannot make .* no structural type */ , 10)
+
+	type M0 map[string]int
+	_ = make(map[string]int)
+	_ = make(M0)
+	_ = make(M1)
+	_ = make(M1, 10)
+	_ = make/* ERROR expects 1 or 2 arguments */(M1, 10, 20)
+	_ = make(M2 /* ERROR cannot make .* no structural type */ )
+
+	type C0 chan int
+	_ = make(chan int)
+	_ = make(C0)
+	_ = make(C1)
+	_ = make(C1, 10)
+	_ = make/* ERROR expects 1 or 2 arguments */(C1, 10, 20)
+	_ = make(C2 /* ERROR cannot make .* no structural type */ )
 }
 
 // unsafe.Alignof
diff --git a/test/typeparam/builtins.go b/test/typeparam/builtins.go
index 819588b07d..844cdae8ab 100644
--- a/test/typeparam/builtins.go
+++ b/test/typeparam/builtins.go
@@ -19,19 +19,19 @@ type C3 interface{ chan int | chan float32 }
 type C4 interface{ chan int | chan<- int }
 type C5[T any] interface{ ~chan T | chan<- T }
 
-func _[T C1](ch T) {
+func f1[T C1](ch T) {
 	close(ch)
 }
 
-func _[T C3](ch T) {
+func f2[T C3](ch T) {
 	close(ch)
 }
 
-func _[T C4](ch T) {
+func f3[T C4](ch T) {
 	close(ch)
 }
 
-func _[T C5[X], X any](ch T) {
+func f4[T C5[X], X any](ch T) {
 	close(ch)
 }
 
@@ -45,61 +45,56 @@ type M2 interface {
 type M3 interface{ map[string]int | map[rune]int }
 type M4[K comparable, V any] interface{ map[K]V | map[rune]V }
 
-func _[T M1](m T) {
+func g1[T M1](m T) {
 	delete(m, "foo")
 }
 
-func _[T M2](m T) {
+func g2[T M2](m T) {
 	delete(m, "foo")
 }
 
-func _[T M4[rune, V], V any](m T) {
+func g3[T M4[rune, V], V any](m T) {
 	delete(m, 'k')
 }
 
 // make
 
-type Bmc interface {
-	~map[rune]string | ~chan int
-}
-
-type Bms interface {
-	~map[string]int | ~[]int
-}
-
-type Bcs interface {
-	~chan bool | ~[]float64
-}
+func m1[
+	S1 interface{ []int },
+	S2 interface{ []int | chan int },
 
-type Bss interface {
-	~[]int | ~[]string
-}
+	M1 interface{ map[string]int },
+	M2 interface{ map[string]int | chan int },
 
-func _[T Bmc]() {
-	_ = make(T)
-	_ = make(T, 10)
-}
+	C1 interface{ chan int },
+	C2 interface{ chan int | chan string },
+]() {
+	type S0 []int
+	_ = make([]int, 10)
+	_ = make(S0, 10)
+	_ = make(S1, 10)
+	_ = make(S1, 10, 20)
 
-func _[T Bms]() {
-	_ = make(T, 10)
-}
-
-func _[T Bcs]() {
-	_ = make(T, 10)
-}
+	type M0 map[string]int
+	_ = make(map[string]int)
+	_ = make(M0)
+	_ = make(M1)
+	_ = make(M1, 10)
 
-func _[T Bss]() {
-	_ = make(T, 10)
-	_ = make(T, 10, 20)
+	type C0 chan int
+	_ = make(chan int)
+	_ = make(C0)
+	_ = make(C1)
+	_ = make(C1, 10)
 }
 
 // len/cap
 
 type Slice[T any] interface {
-	type []T
+	[]T
 }
 
-func _[T any, S Slice[T]]() {
+func c1[T any, S Slice[T]]() {
 	x := make(S, 5, 10)
 	_ = len(x)
 	_ = cap(x)
@@ -107,7 +102,7 @@ func _[T any, S Slice[T]]() {
 
 // append
 
-func _[T any, S Slice[T]]() {
+func a1[T any, S Slice[T]]() {
 	x := make(S, 5)
 	y := make(S, 2)
 	var z T