go/types, types2: remove uses of "type list" and "operational type" (cleanup)

Fixes #49193.

Change-Id: Ief31ea6b3dddf9452efb94763c89b8639aa3ce9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/394656
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/types2/testdata/check/funcinference.go

@@ -85,7 +85,7 @@ type Setter[B any] interface {
 func FromStrings[T interface{}, PT Setter[T]](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
-		// The type of &result[i] is *T which is in the type list
+		// The type of &result[i] is *T which is in the type set
 		// of Setter, so we can convert it to PT.
 		p := PT(&result[i])
 		// PT has a Set method.

src/cmd/compile/internal/types2/testdata/check/issues1.go

@@ -51,9 +51,8 @@ func _() {
 }
 
 // When a type parameter is used as an argument to instantiate a parameterized
-// type with a type list constraint, all of the type argument's types in its
-// bound, but at least one (!), must be in the type list of the bound of the
-// corresponding parameterized type's type parameter.
+// type, the type argument's type set must be a subset of the instantiated type
+// parameter's type set.
 type T1[P interface{~uint}] struct{}
 
 func _[P any]() {
@@ -150,7 +149,7 @@ type inf2[T any] struct{ inf2 /* ERROR illegal cycle */ [T] }
 // The implementation of conversions T(x) between integers and floating-point
 // numbers checks that both T and x have either integer or floating-point
 // type. When the type of T or x is a type parameter, the respective simple
-// predicate disjunction in the implementation was wrong because if a type list
+// predicate disjunction in the implementation was wrong because if a type set
 // contains both an integer and a floating-point type, the type parameter is
 // neither an integer or a floating-point number.
 func convert[T1, T2 interface{~int | ~uint | ~float32}](v T1) T2 {
@@ -183,14 +182,12 @@ func _[T interface{}, PT interface{~*T}] (x T) PT {
     return &x
 }
 
-// Indexing of generic types containing type parameters in their type list:
+// Indexing of type parameters containing type parameters in their constraint terms:
 func at[T interface{ ~[]E }, E interface{}](x T, i int) E {
         return x[i]
 }
 
-// A generic type inside a function acts like a named type. Its underlying
-// type is itself, its "operational type" is defined by the type list in
-// the tybe bound, if any.
+// Conversion of a local type to a type parameter.
 func _[T interface{~int}](x T) {
 	type myint int
 	var _ int = int(x)
@@ -198,19 +195,19 @@ func _[T interface{~int}](x T) {
 	var _ T = T(myint(42))
 }
 
-// Indexing a generic type with an array type bound checks length.
+// Indexing a type parameter with an array type bound checks length.
 // (Example by mdempsky@.)
 func _[T interface { ~[10]int }](x T) {
 	_ = x[9] // ok
 	_ = x[20 /* ERROR out of bounds */ ]
 }
 
-// Pointer indirection of a generic type.
+// Pointer indirection of a type parameter.
 func _[T interface{ ~*int }](p T) int {
 	return *p
 }
 
-// Channel sends and receives on generic types.
+// Channel sends and receives on type parameters.
 func _[T interface{ ~chan int }](ch T) int {
 	ch <- 0
 	return <- ch
@@ -229,11 +226,11 @@ func _[T interface{ func()|F1|F2 }](f T) {
 	go f()
 }
 
-// We must compare against the underlying type of type list entries
-// when checking if a constraint is satisfied by a type. The under-
-// lying type of each type list entry must be computed after the
-// interface has been instantiated as its typelist may contain a
-// type parameter that was substituted with a defined type.
+// We must compare against the (possibly underlying) types of term list
+// elements when checking if a constraint is satisfied by a type.
+// The underlying type of each term must be computed after the
+// interface has been instantiated as its constraint may contain
+// a type parameter that was substituted with a defined type.
 // Test case from an (originally) failing example.
 
 type sliceOf[E any] interface{ ~[]E }

src/cmd/compile/internal/types2/testdata/check/typeinst1.go

@@ -173,7 +173,9 @@ type _ interface {
 }
 
 // Interface term lists can contain any type, incl. *Named types.
-// Verify that we use the underlying type to compute the operational type.
+// Verify that we use the underlying type(s) of the type(s) in the
+// term list when determining if an operation is permitted.
+
 type MyInt int
 func add1[T interface{MyInt}](x T) T {
 	return x + 1
@@ -271,10 +273,10 @@ func gg[T any]() {}
 func hh[T ~int]() {}
 
 func _[T none]() {
-        _ = ff[int /* ERROR cannot implement none \(empty type set\) */ ]
-        _ = ff[T]  // pathological but ok because T's type set is empty, too
-        _ = gg[int]
-        _ = gg[T]
+	_ = ff[int /* ERROR cannot implement none \(empty type set\) */ ]
+	_ = ff[T]  // pathological but ok because T's type set is empty, too
+	_ = gg[int]
+	_ = gg[T]
 	_ = hh[int]
 	_ = hh[T]
 }

src/cmd/compile/internal/types2/testdata/fixedbugs/issue42758.go

@@ -22,7 +22,7 @@ type constraint interface {
 
 func _[T constraint](x interface{}){
 	switch x.(type) {
-	case T: // ok to use a type parameter even if type list contains int
+	case T: // ok to use a type parameter even if type set contains int
 	case int:
 	}
 }

src/go/types/testdata/check/funcinference.go

@@ -85,7 +85,7 @@ type Setter[B any] interface {
 func FromStrings[T interface{}, PT Setter[T]](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
-		// The type of &result[i] is *T which is in the type list
+		// The type of &result[i] is *T which is in the type set
 		// of Setter, so we can convert it to PT.
 		p := PT(&result[i])
 		// PT has a Set method.

src/go/types/testdata/check/issues1.go

@@ -31,12 +31,12 @@ type C[T any] interface {
 
 // using type bound C
 func _[T C[T]](x *T) {
-	x.m  /* ERROR x\.m undefined */ ()
+	x.m /* ERROR x\.m undefined */ ()
 }
 
 // using an interface literal as bound
 func _[T interface{ m() }](x *T) {
-	x.m  /* ERROR x\.m undefined */ ()
+	x.m /* ERROR x\.m undefined */ ()
 }
 
 func f2[_ interface{ m1(); m2() }]() {}
@@ -51,9 +51,8 @@ func _() {
 }
 
 // When a type parameter is used as an argument to instantiate a parameterized
-// type with a type set constraint, all of the type argument's types in its
-// bound, but at least one (!), must be in the type set of the bound of the
-// corresponding parameterized type's type parameter.
+// type, the type argument's type set must be a subset of the instantiated type
+// parameter's type set.
 type T1[P interface{~uint}] struct{}
 
 func _[P any]() {
@@ -150,7 +149,7 @@ type inf2[T any] struct{ inf2 /* ERROR illegal cycle */ [T] }
 // The implementation of conversions T(x) between integers and floating-point
 // numbers checks that both T and x have either integer or floating-point
 // type. When the type of T or x is a type parameter, the respective simple
-// predicate disjunction in the implementation was wrong because if a term list
+// predicate disjunction in the implementation was wrong because if a type set
 // contains both an integer and a floating-point type, the type parameter is
 // neither an integer or a floating-point number.
 func convert[T1, T2 interface{~int | ~uint | ~float32}](v T1) T2 {
@@ -183,14 +182,12 @@ func _[T interface{}, PT interface{~*T}] (x T) PT {
     return &x
 }
 
-// Indexing of generic types containing type parameters in their term list:
+// Indexing of type parameters containing type parameters in their constraint terms:
 func at[T interface{ ~[]E }, E interface{}](x T, i int) E {
         return x[i]
 }
 
-// A generic type inside a function acts like a named type. Its underlying
-// type is itself, its "operational type" is defined by the term list in
-// the tybe bound, if any.
+// Conversion of a local type to a type parameter.
 func _[T interface{~int}](x T) {
 	type myint int
 	var _ int = int(x)
@@ -198,19 +195,19 @@ func _[T interface{~int}](x T) {
 	var _ T = T(myint(42))
 }
 
-// Indexing a generic type with an array type bound checks length.
+// Indexing a type parameter with an array type bound checks length.
 // (Example by mdempsky@.)
 func _[T interface { ~[10]int }](x T) {
 	_ = x[9] // ok
 	_ = x[20 /* ERROR out of bounds */ ]
 }
 
-// Pointer indirection of a generic type.
+// Pointer indirection of a type parameter.
 func _[T interface{ ~*int }](p T) int {
 	return *p
 }
 
-// Channel sends and receives on generic types.
+// Channel sends and receives on type parameters.
 func _[T interface{ ~chan int }](ch T) int {
 	ch <- 0
 	return <- ch
@@ -229,11 +226,11 @@ func _[T interface{ func()|F1|F2 }](f T) {
 	go f()
 }
 
-// We must compare against the underlying type of term list entries
-// when checking if a constraint is satisfied by a type. The under-
-// lying type of each term list entry must be computed after the
-// interface has been instantiated as its typelist may contain a
-// type parameter that was substituted with a defined type.
+// We must compare against the (possibly underlying) types of term list
+// elements when checking if a constraint is satisfied by a type.
+// The underlying type of each term must be computed after the
+// interface has been instantiated as its constraint may contain
+// a type parameter that was substituted with a defined type.
 // Test case from an (originally) failing example.
 
 type sliceOf[E any] interface{ ~[]E }

src/go/types/testdata/check/typeinst1.go

@@ -169,11 +169,13 @@ type _ interface {
 }
 
 type _ interface {
-	~struct{f int} | ~struct{g int} | ~ /* ERROR overlapping terms */ struct {f int}
+	~struct{f int} | ~struct{g int} | ~ /* ERROR overlapping terms */ struct{f int}
 }
 
 // Interface term lists can contain any type, incl. *Named types.
-// Verify that we use the underlying type to compute the operational type.
+// Verify that we use the underlying type(s) of the type(s) in the
+// term list when determining if an operation is permitted.
+
 type MyInt int
 func add1[T interface{MyInt}](x T) T {
 	return x + 1
@@ -271,10 +273,10 @@ func gg[T any]() {}
 func hh[T ~int]() {}
 
 func _[T none]() {
-        _ = ff[int /* ERROR cannot implement none \(empty type set\) */ ]
-        _ = ff[T]  // pathological but ok because T's type set is empty, too
-        _ = gg[int]
-        _ = gg[T]
+	_ = ff[int /* ERROR cannot implement none \(empty type set\) */ ]
+	_ = ff[T]  // pathological but ok because T's type set is empty, too
+	_ = gg[int]
+	_ = gg[T]
 	_ = hh[int]
 	_ = hh[T]
 }

src/go/types/testdata/fixedbugs/issue42758.go

@@ -22,7 +22,7 @@ type constraint interface {
 
 func _[T constraint](x interface{}){
 	switch x.(type) {
-	case T: // ok to use a type parameter even if type list contains int
+	case T: // ok to use a type parameter even if type set contains int
 	case int:
 	}
 }