go/types, types2: rename structuralType/String to coreType/String

This is a pure rename of the respective Go functions/methods
with corresponding adjustments to error messages and tests.
A couple of comments were manually rephrased.

With this change, the implementation and error messages match
the latest spec.

No functionality change.

Change-Id: Iaa92a08b64756356fb2c5abdaca5c943c9105c96
Reviewed-on: https://go-review.googlesource.com/c/go/+/384618
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/noder/expr.go

@@ -332,13 +332,13 @@ func (g *irgen) exprs(exprs []syntax.Expr) []ir.Node {
 }
 
 func (g *irgen) compLit(typ types2.Type, lit *syntax.CompositeLit) ir.Node {
-	if ptr, ok := types2.StructuralType(typ).(*types2.Pointer); ok {
+	if ptr, ok := types2.CoreType(typ).(*types2.Pointer); ok {
 		n := ir.NewAddrExpr(g.pos(lit), g.compLit(ptr.Elem(), lit))
 		n.SetOp(ir.OPTRLIT)
 		return typed(g.typ(typ), n)
 	}
 
-	_, isStruct := types2.StructuralType(typ).(*types2.Struct)
+	_, isStruct := types2.CoreType(typ).(*types2.Struct)
 
 	exprs := make([]ir.Node, len(lit.ElemList))
 	for i, elem := range lit.ElemList {

src/cmd/compile/internal/noder/writer.go

@@ -1338,10 +1338,10 @@ func (w *writer) compLit(lit *syntax.CompositeLit) {
 	w.typ(tv.Type)
 
 	typ := tv.Type
-	if ptr, ok := types2.StructuralType(typ).(*types2.Pointer); ok {
+	if ptr, ok := types2.CoreType(typ).(*types2.Pointer); ok {
 		typ = ptr.Elem()
 	}
-	str, isStruct := types2.StructuralType(typ).(*types2.Struct)
+	str, isStruct := types2.CoreType(typ).(*types2.Struct)
 
 	w.len(len(lit.ElemList))
 	for i, elem := range lit.ElemList {

src/cmd/compile/internal/types2/builtins.go

@@ -82,7 +82,7 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		// of S and the respective parameter passing rules apply."
 		S := x.typ
 		var T Type
-		if s, _ := structuralType(S).(*Slice); s != nil {
+		if s, _ := coreType(S).(*Slice); s != nil {
 			T = s.elem
 		} else {
 			var cause string
@@ -90,10 +90,10 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 			case x.isNil():
 				cause = "have untyped nil"
 			case isTypeParam(S):
-				if u := structuralType(S); u != nil {
+				if u := coreType(S); u != nil {
-					cause = check.sprintf("%s has structural type %s", x, u)
+					cause = check.sprintf("%s has core type %s", x, u)
 				} else {
-					cause = check.sprintf("%s has no structural type", x)
+					cause = check.sprintf("%s has no core type", x)
 				}
 			default:
 				cause = check.sprintf("have %s", x)
@@ -115,7 +115,7 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 				if x.mode == invalid {
 					return
 				}
-				if t := structuralString(x.typ); t != nil && isString(t) {
+				if t := coreString(x.typ); t != nil && isString(t) {
 					if check.Types != nil {
 						sig := makeSig(S, S, x.typ)
 						sig.variadic = true
@@ -345,14 +345,14 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 
 	case _Copy:
 		// copy(x, y []T) int
-		dst, _ := structuralType(x.typ).(*Slice)
+		dst, _ := coreType(x.typ).(*Slice)
 
 		var y operand
 		arg(&y, 1)
 		if y.mode == invalid {
 			return
 		}
-		src0 := structuralString(y.typ)
+		src0 := coreString(y.typ)
 		if src0 != nil && isString(src0) {
 			src0 = NewSlice(universeByte)
 		}
@@ -486,13 +486,13 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		}
 
 		var min int // minimum number of arguments
-		switch structuralType(T).(type) {
+		switch coreType(T).(type) {
 		case *Slice:
 			min = 2
 		case *Map, *Chan:
 			min = 1
 		case nil:
-			check.errorf(arg0, invalidArg+"cannot make %s: no structural type", arg0)
+			check.errorf(arg0, invalidArg+"cannot make %s: no core type", arg0)
 			return
 		default:
 			check.errorf(arg0, invalidArg+"cannot make %s; type must be slice, map, or channel", arg0)

src/cmd/compile/internal/types2/call.go

@@ -168,7 +168,7 @@ func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
 	cgocall := x.mode == cgofunc
 
 	// a type parameter may be "called" if all types have the same signature
-	sig, _ := structuralType(x.typ).(*Signature)
+	sig, _ := coreType(x.typ).(*Signature)
 	if sig == nil {
 		check.errorf(x, invalidOp+"cannot call non-function %s", x)
 		x.mode = invalid

src/cmd/compile/internal/types2/compilersupport.go

@@ -19,12 +19,12 @@ func AsSignature(t Type) *Signature {
 	return u
 }
 
-// If typ is a type parameter, structuralType returns the single underlying
+// If typ is a type parameter, CoreType returns the single underlying
 // type of all types in the corresponding type constraint if it exists, or
 // nil otherwise. If the type set contains only unrestricted and restricted
 // channel types (with identical element types), the single underlying type
 // is the restricted channel type if the restrictions are always the same.
-// If typ is not a type parameter, structuralType returns the underlying type.
+// If typ is not a type parameter, CoreType returns the underlying type.
-func StructuralType(t Type) Type {
+func CoreType(t Type) Type {
-	return structuralType(t)
+	return coreType(t)
 }

src/cmd/compile/internal/types2/expr.go

@@ -182,9 +182,9 @@ func (check *Checker) unary(x *operand, e *syntax.Operation) {
 		return
 
 	case syntax.Recv:
-		u := structuralType(x.typ)
+		u := coreType(x.typ)
 		if u == nil {
-			check.errorf(x, invalidOp+"cannot receive from %s: no structural type", x)
+			check.errorf(x, invalidOp+"cannot receive from %s: no core type", x)
 			x.mode = invalid
 			return
 		}
@@ -1359,7 +1359,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 		case hint != nil:
 			// no composite literal type present - use hint (element type of enclosing type)
 			typ = hint
-			base, _ = deref(structuralType(typ)) // *T implies &T{}
+			base, _ = deref(coreType(typ)) // *T implies &T{}
 
 		default:
 			// TODO(gri) provide better error messages depending on context
@@ -1367,7 +1367,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 			goto Error
 		}
 
-		switch utyp := structuralType(base).(type) {
+		switch utyp := coreType(base).(type) {
 		case *Struct:
 			// Prevent crash if the struct referred to is not yet set up.
 			// See analogous comment for *Array.

src/cmd/compile/internal/types2/index.go

@@ -213,9 +213,9 @@ func (check *Checker) sliceExpr(x *operand, e *syntax.SliceExpr) {
 
 	valid := false
 	length := int64(-1) // valid if >= 0
-	switch u := structuralString(x.typ).(type) {
+	switch u := coreString(x.typ).(type) {
 	case nil:
-		check.errorf(x, invalidOp+"cannot slice %s: %s has no structural type", x, x.typ)
+		check.errorf(x, invalidOp+"cannot slice %s: %s has no core type", x, x.typ)
 		x.mode = invalid
 		return
 

src/cmd/compile/internal/types2/infer.go

@@ -416,11 +416,11 @@ func (check *Checker) inferB(pos syntax.Pos, tparams []*TypeParam, targs []Type)
 		}
 	}
 
-	// If a constraint has a structural type, unify the corresponding type parameter with it.
+	// If a constraint has a core type, unify the corresponding type parameter with it.
 	for _, tpar := range tparams {
-		sbound := structuralType(tpar)
+		sbound := coreType(tpar)
 		if sbound != nil {
-			// If the structural type is the underlying type of a single
+			// If the core type is the underlying type of a single
 			// defined type in the constraint, use that defined type instead.
 			if named, _ := tpar.singleType().(*Named); named != nil {
 				sbound = named
@@ -435,7 +435,7 @@ func (check *Checker) inferB(pos syntax.Pos, tparams []*TypeParam, targs []Type)
 	}
 
 	// u.x.types() now contains the incoming type arguments plus any additional type
-	// arguments which were inferred from structural types. The newly inferred non-
+	// arguments which were inferred from core types. The newly inferred non-
 	// nil entries may still contain references to other type parameters.
 	// For instance, for [A any, B interface{ []C }, C interface{ *A }], if A == int
 	// was given, unification produced the type list [int, []C, *A]. We eliminate the
@@ -504,8 +504,8 @@ func (check *Checker) inferB(pos syntax.Pos, tparams []*TypeParam, targs []Type)
 	}
 
 	// Once nothing changes anymore, we may still have type parameters left;
-	// e.g., a structural constraint *P may match a type parameter Q but we
+	// e.g., a constraint with core type *P may match a type parameter Q but
-	// don't have any type arguments to fill in for *P or Q (issue #45548).
+	// we don't have any type arguments to fill in for *P or Q (issue #45548).
 	// Don't let such inferences escape, instead nil them out.
 	for i, typ := range types {
 		if typ != nil && isParameterized(tparams, typ) {

src/cmd/compile/internal/types2/lookup.go

@@ -66,12 +66,12 @@ func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
 
 	obj, index, indirect = lookupFieldOrMethod(T, addressable, pkg, name, false)
 
-	// If we didn't find anything and if we have a type parameter with a structural constraint,
+	// If we didn't find anything and if we have a type parameter with a core type,
-	// see if there is a matching field (but not a method, those need to be declared explicitly
+	// see if there is a matching field (but not a method, those need to be declared
-	// in the constraint). If the structural constraint is a named pointer type (see above), we
+	// explicitly in the constraint). If the constraint is a named pointer type (see
-	// are ok here because only fields are accepted as results.
+	// above), we are ok here because only fields are accepted as results.
 	if obj == nil && isTypeParam(T) {
-		if t := structuralType(T); t != nil {
+		if t := coreType(T); t != nil {
 			obj, index, indirect = lookupFieldOrMethod(t, addressable, pkg, name, false)
 			if _, ok := obj.(*Var); !ok {
 				obj, index, indirect = nil, nil, false // accept fields (variables) only

src/cmd/compile/internal/types2/predicates.go

@@ -31,7 +31,7 @@ func isBasic(t Type, info BasicInfo) bool {
 // The allX predicates below report whether t is an X.
 // If t is a type parameter the result is true if isX is true
 // for all specified types of the type parameter's type set.
-// allX is an optimized version of isX(structuralType(t)) (which
+// allX is an optimized version of isX(coreType(t)) (which
 // is the same as underIs(t, isX)).
 
 func allBoolean(t Type) bool         { return allBasic(t, IsBoolean) }
@@ -45,7 +45,7 @@ func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) }
 // allBasic reports whether under(t) is a basic type with the specified info.
 // If t is a type parameter, the result is true if isBasic(t, info) is true
 // for all specific types of the type parameter's type set.
-// allBasic(t, info) is an optimized version of isBasic(structuralType(t), info).
+// allBasic(t, info) is an optimized version of isBasic(coreType(t), info).
 func allBasic(t Type, info BasicInfo) bool {
 	if tpar, _ := t.(*TypeParam); tpar != nil {
 		return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) })

src/cmd/compile/internal/types2/stmt.go

@@ -409,9 +409,9 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		if ch.mode == invalid || val.mode == invalid {
 			return
 		}
-		u := structuralType(ch.typ)
+		u := coreType(ch.typ)
 		if u == nil {
-			check.errorf(s, invalidOp+"cannot send to %s: no structural type", &ch)
+			check.errorf(s, invalidOp+"cannot send to %s: no core type", &ch)
 			return
 		}
 		uch, _ := u.(*Chan)
@@ -835,9 +835,9 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 	// determine key/value types
 	var key, val Type
 	if x.mode != invalid {
-		// Ranging over a type parameter is permitted if it has a structural type.
+		// Ranging over a type parameter is permitted if it has a core type.
 		var cause string
-		u := structuralType(x.typ)
+		u := coreType(x.typ)
 		if t, _ := u.(*Chan); t != nil {
 			if sValue != nil {
 				check.softErrorf(sValue, "range over %s permits only one iteration variable", &x)
@@ -852,7 +852,7 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 				// ok to continue
 			}
 			if u == nil {
-				cause = check.sprintf("%s has no structural type", x.typ)
+				cause = check.sprintf("%s has no core type", x.typ)
 			}
 		}
 		key, val = rangeKeyVal(u)

src/cmd/compile/internal/types2/testdata/check/builtins.go2

@@ -148,7 +148,7 @@ func _[
 	_ = 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 S2: no structural type */ , 10)
+	_ = make(S2 /* ERROR cannot make S2: no core type */ , 10)
 
 	type M0 map[string]int
 	_ = make(map[string]int)
@@ -156,7 +156,7 @@ func _[
 	_ = make(M1)
 	_ = make(M1, 10)
 	_ = make/* ERROR expects 1 or 2 arguments */(M1, 10, 20)
-	_ = make(M2 /* ERROR cannot make M2: no structural type */ )
+	_ = make(M2 /* ERROR cannot make M2: no core type */ )
 
 	type C0 chan int
 	_ = make(chan int)
@@ -164,7 +164,7 @@ func _[
 	_ = make(C1)
 	_ = make(C1, 10)
 	_ = make/* ERROR expects 1 or 2 arguments */(C1, 10, 20)
-	_ = make(C2 /* ERROR cannot make C2: no structural type */ )
+	_ = make(C2 /* ERROR cannot make C2: no core type */ )
 	_ = make(C3)
 }
 

src/cmd/compile/internal/types2/testdata/check/typeparams.go2

@@ -134,11 +134,11 @@ func _[T interface{ ~string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3
 type myByte1 []byte
 type myByte2 []byte
 func _[T interface{ []byte | myByte1 | myByte2 }] (x T, i, j, k int) { var _ T = x[i:j:k] }
-func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x[ /* ERROR no structural type */ i:j:k] }
+func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x[ /* ERROR no core type */ i:j:k] }
 
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j] }
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3-index slice of string */ ] }
-func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x[ /* ERROR no structural type */ i:j] }
+func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x[ /* ERROR no core type */ i:j] }
 
 // len/cap built-ins
 
@@ -230,7 +230,7 @@ func _[
         for _, _ = range s1 {}
 
         var s2 S2
-        for range s2 /* ERROR cannot range over s2.*no structural type */ {}
+        for range s2 /* ERROR cannot range over s2.*no core type */ {}
 
         var a0 []int
         for range a0 {}
@@ -243,7 +243,7 @@ func _[
         for _, _ = range a1 {}
 
         var a2 A2
-        for range a2 /* ERROR cannot range over a2.*no structural type */ {}
+        for range a2 /* ERROR cannot range over a2.*no core type */ {}
 
         var p0 *[10]int
         for range p0 {}
@@ -256,7 +256,7 @@ func _[
         for _, _ = range p1 {}
 
         var p2 P2
-        for range p2 /* ERROR cannot range over p2.*no structural type */ {}
+        for range p2 /* ERROR cannot range over p2.*no core type */ {}
 
         var m0 map[string]int
         for range m0 {}
@@ -269,7 +269,7 @@ func _[
         for _, _ = range m1 {}
 
         var m2 M2
-        for range m2 /* ERROR cannot range over m2.*no structural type */ {}
+        for range m2 /* ERROR cannot range over m2.*no core type */ {}
 }
 
 // type inference checks

src/cmd/compile/internal/types2/testdata/examples/inference.go2

@@ -113,7 +113,7 @@ func _() {
 	// from the first one through constraint type inference.
 	related3[int]()
 
-	// The inferred type is the structural type of the Slice
+	// The inferred type is the core type of the Slice
 	// type parameter.
 	var _ []int = related3[int]()
 

src/cmd/compile/internal/types2/testdata/examples/types.go2

@@ -292,7 +292,7 @@ func _[T interface{~int|~float64}]() {
 
 // It is possible to create composite literals of type parameter
 // type as long as it's possible to create a composite literal
-// of the structural type of the type parameter's constraint.
+// of the core type of the type parameter's constraint.
 func _[P interface{ ~[]int }]() P {
 	return P{}
 	return P{1, 2, 3}
@@ -307,7 +307,7 @@ func _[P interface{ ~[]E }, E interface{ map[string]P } ]() P {
 }
 
 // This is a degenerate case with a singleton type set, but we can create
-// composite literals even if the structural type is a defined type.
+// composite literals even if the core type is a defined type.
 type MyInts []int
 
 func _[P MyInts]() P {

src/cmd/compile/internal/types2/testdata/fixedbugs/issue43671.go2

@@ -12,7 +12,7 @@ type C4 interface{ chan int | chan<- int }
 type C5[T any] interface{ ~chan T | <-chan T }
 
 func _[T any](ch T) {
-	<-ch // ERROR cannot receive from ch .* no structural type
+	<-ch // ERROR cannot receive from ch .* no core type
 }
 
 func _[T C0](ch T) {
@@ -28,7 +28,7 @@ func _[T C2](ch T) {
 }
 
 func _[T C3](ch T) {
-	<-ch // ERROR cannot receive from ch .* no structural type
+	<-ch // ERROR cannot receive from ch .* no core type
 }
 
 func _[T C4](ch T) {

src/cmd/compile/internal/types2/testdata/fixedbugs/issue47115.go2

@@ -12,7 +12,7 @@ type C4 interface{ chan int | chan<- int }
 type C5[T any] interface{ ~chan T | chan<- T }
 
 func _[T any](ch T) {
-	ch /* ERROR cannot send to ch .* no structural type */ <- 0
+	ch /* ERROR cannot send to ch .* no core type */ <- 0
 }
 
 func _[T C0](ch T) {
@@ -28,7 +28,7 @@ func _[T C2](ch T) {
 }
 
 func _[T C3](ch T) {
-	ch /* ERROR cannot send to ch .* no structural type */ <- 0
+	ch /* ERROR cannot send to ch .* no core type */ <- 0
 }
 
 func _[T C4](ch T) {

src/cmd/compile/internal/types2/testdata/fixedbugs/issue49735.go2

@@ -6,6 +6,6 @@ package p
 
 func _[P1 any, P2 ~byte](s1 P1, s2 P2) {
         _ = append(nil /* ERROR first argument to append must be a slice; have untyped nil */ , 0)
-        _ = append(s1 /* ERROR s1 .* has no structural type */ , 0)
+        _ = append(s1 /* ERROR s1 .* has no core type */ , 0)
-        _ = append(s2 /* ERROR s2 .* has structural type byte */ , 0)
+        _ = append(s2 /* ERROR s2 .* has core type byte */ , 0)
 }

src/cmd/compile/internal/types2/testdata/fixedbugs/issue50417.go2

@@ -51,7 +51,7 @@ func f2[P interface{ Sfm; m() }](p P) {
 
 var _ = f2[Sfm]
 
-// special case: structural type is a named pointer type
+// special case: core type is a named pointer type
 
 type PSfm *Sfm
 

src/cmd/compile/internal/types2/type.go

@@ -27,13 +27,13 @@ func under(t Type) Type {
 	return t.Underlying()
 }
 
-// If t is not a type parameter, structuralType returns the underlying type.
+// If t is not a type parameter, coreType returns the underlying type.
-// If t is a type parameter, structuralType returns the single underlying
+// If t is a type parameter, coreType returns the single underlying
 // type of all types in its type set if it exists, or nil otherwise. If the
 // type set contains only unrestricted and restricted channel types (with
 // identical element types), the single underlying type is the restricted
 // channel type if the restrictions are always the same, or nil otherwise.
-func structuralType(t Type) Type {
+func coreType(t Type) Type {
 	tpar, _ := t.(*TypeParam)
 	if tpar == nil {
 		return under(t)
@@ -59,10 +59,10 @@ func structuralType(t Type) Type {
 	return nil
 }
 
-// structuralString is like structuralType but also considers []byte
+// coreString is like coreType but also considers []byte
 // and strings as identical. In this case, if successful and we saw
 // a string, the result is of type (possibly untyped) string.
-func structuralString(t Type) Type {
+func coreString(t Type) Type {
 	tpar, _ := t.(*TypeParam)
 	if tpar == nil {
 		return under(t) // string or untyped string

src/go/types/builtins.go

@@ -83,7 +83,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// of S and the respective parameter passing rules apply."
 		S := x.typ
 		var T Type
-		if s, _ := structuralType(S).(*Slice); s != nil {
+		if s, _ := coreType(S).(*Slice); s != nil {
 			T = s.elem
 		} else {
 			var cause string
@@ -91,10 +91,10 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			case x.isNil():
 				cause = "have untyped nil"
 			case isTypeParam(S):
-				if u := structuralType(S); u != nil {
+				if u := coreType(S); u != nil {
-					cause = check.sprintf("%s has structural type %s", x, u)
+					cause = check.sprintf("%s has core type %s", x, u)
 				} else {
-					cause = check.sprintf("%s has no structural type", x)
+					cause = check.sprintf("%s has no core type", x)
 				}
 			default:
 				cause = check.sprintf("have %s", x)
@@ -116,7 +116,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 				if x.mode == invalid {
 					return
 				}
-				if t := structuralString(x.typ); t != nil && isString(t) {
+				if t := coreString(x.typ); t != nil && isString(t) {
 					if check.Types != nil {
 						sig := makeSig(S, S, x.typ)
 						sig.variadic = true
@@ -350,14 +350,14 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 
 	case _Copy:
 		// copy(x, y []T) int
-		dst, _ := structuralType(x.typ).(*Slice)
+		dst, _ := coreType(x.typ).(*Slice)
 
 		var y operand
 		arg(&y, 1)
 		if y.mode == invalid {
 			return
 		}
-		src0 := structuralString(y.typ)
+		src0 := coreString(y.typ)
 		if src0 != nil && isString(src0) {
 			src0 = NewSlice(universeByte)
 		}
@@ -495,13 +495,13 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		}
 
 		var min int // minimum number of arguments
-		switch structuralType(T).(type) {
+		switch coreType(T).(type) {
 		case *Slice:
 			min = 2
 		case *Map, *Chan:
 			min = 1
 		case nil:
-			check.errorf(arg0, _InvalidMake, "cannot make %s: no structural type", arg0)
+			check.errorf(arg0, _InvalidMake, "cannot make %s: no core type", arg0)
 			return
 		default:
 			check.invalidArg(arg0, _InvalidMake, "cannot make %s; type must be slice, map, or channel", arg0)

src/go/types/call.go

@@ -171,7 +171,7 @@ func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
 	cgocall := x.mode == cgofunc
 
 	// a type parameter may be "called" if all types have the same signature
-	sig, _ := structuralType(x.typ).(*Signature)
+	sig, _ := coreType(x.typ).(*Signature)
 	if sig == nil {
 		check.invalidOp(x, _InvalidCall, "cannot call non-function %s", x)
 		x.mode = invalid

src/go/types/expr.go

@@ -173,9 +173,9 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
 		return
 
 	case token.ARROW:
-		u := structuralType(x.typ)
+		u := coreType(x.typ)
 		if u == nil {
-			check.invalidOp(x, _InvalidReceive, "cannot receive from %s: no structural type", x)
+			check.invalidOp(x, _InvalidReceive, "cannot receive from %s: no core type", x)
 			x.mode = invalid
 			return
 		}
@@ -1338,7 +1338,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		case hint != nil:
 			// no composite literal type present - use hint (element type of enclosing type)
 			typ = hint
-			base, _ = deref(structuralType(typ)) // *T implies &T{}
+			base, _ = deref(coreType(typ)) // *T implies &T{}
 
 		default:
 			// TODO(gri) provide better error messages depending on context
@@ -1346,7 +1346,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 			goto Error
 		}
 
-		switch utyp := structuralType(base).(type) {
+		switch utyp := coreType(base).(type) {
 		case *Struct:
 			// Prevent crash if the struct referred to is not yet set up.
 			// See analogous comment for *Array.

src/go/types/index.go

@@ -214,9 +214,9 @@ func (check *Checker) sliceExpr(x *operand, e *ast.SliceExpr) {
 
 	valid := false
 	length := int64(-1) // valid if >= 0
-	switch u := structuralString(x.typ).(type) {
+	switch u := coreString(x.typ).(type) {
 	case nil:
-		check.invalidOp(x, _NonSliceableOperand, "cannot slice %s: %s has no structural type", x, x.typ)
+		check.invalidOp(x, _NonSliceableOperand, "cannot slice %s: %s has no core type", x, x.typ)
 		x.mode = invalid
 		return
 

src/go/types/infer.go

@@ -415,11 +415,11 @@ func (check *Checker) inferB(posn positioner, tparams []*TypeParam, targs []Type
 		}
 	}
 
-	// If a constraint has a structural type, unify the corresponding type parameter with it.
+	// If a constraint has a core type, unify the corresponding type parameter with it.
 	for _, tpar := range tparams {
-		sbound := structuralType(tpar)
+		sbound := coreType(tpar)
 		if sbound != nil {
-			// If the structural type is the underlying type of a single
+			// If the core type is the underlying type of a single
 			// defined type in the constraint, use that defined type instead.
 			if named, _ := tpar.singleType().(*Named); named != nil {
 				sbound = named
@@ -434,7 +434,7 @@ func (check *Checker) inferB(posn positioner, tparams []*TypeParam, targs []Type
 	}
 
 	// u.x.types() now contains the incoming type arguments plus any additional type
-	// arguments which were inferred from structural types. The newly inferred non-
+	// arguments which were inferred from core types. The newly inferred non-
 	// nil entries may still contain references to other type parameters.
 	// For instance, for [A any, B interface{ []C }, C interface{ *A }], if A == int
 	// was given, unification produced the type list [int, []C, *A]. We eliminate the
@@ -503,8 +503,8 @@ func (check *Checker) inferB(posn positioner, tparams []*TypeParam, targs []Type
 	}
 
 	// Once nothing changes anymore, we may still have type parameters left;
-	// e.g., a structural constraint *P may match a type parameter Q but we
+	// e.g., a constraint with core type *P may match a type parameter Q but
-	// don't have any type arguments to fill in for *P or Q (issue #45548).
+	// we don't have any type arguments to fill in for *P or Q (issue #45548).
 	// Don't let such inferences escape, instead nil them out.
 	for i, typ := range types {
 		if typ != nil && isParameterized(tparams, typ) {

src/go/types/lookup.go

@@ -66,12 +66,12 @@ func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
 
 	obj, index, indirect = lookupFieldOrMethod(T, addressable, pkg, name, false)
 
-	// If we didn't find anything and if we have a type parameter with a structural constraint,
+	// If we didn't find anything and if we have a type parameter with a core type,
-	// see if there is a matching field (but not a method, those need to be declared explicitly
+	// see if there is a matching field (but not a method, those need to be declared
-	// in the constraint). If the structural constraint is a named pointer type (see above), we
+	// explicitly in the constraint). If the constraint is a named pointer type (see
-	// are ok here because only fields are accepted as results.
+	// above), we are ok here because only fields are accepted as results.
 	if obj == nil && isTypeParam(T) {
-		if t := structuralType(T); t != nil {
+		if t := coreType(T); t != nil {
 			obj, index, indirect = lookupFieldOrMethod(t, addressable, pkg, name, false)
 			if _, ok := obj.(*Var); !ok {
 				obj, index, indirect = nil, nil, false // accept fields (variables) only

src/go/types/predicates.go

@@ -33,7 +33,7 @@ func isBasic(t Type, info BasicInfo) bool {
 // The allX predicates below report whether t is an X.
 // If t is a type parameter the result is true if isX is true
 // for all specified types of the type parameter's type set.
-// allX is an optimized version of isX(structuralType(t)) (which
+// allX is an optimized version of isX(coreType(t)) (which
 // is the same as underIs(t, isX)).
 
 func allBoolean(typ Type) bool         { return allBasic(typ, IsBoolean) }
@@ -47,7 +47,7 @@ func allNumericOrString(typ Type) bool { return allBasic(typ, IsNumeric|IsString
 // allBasic reports whether under(t) is a basic type with the specified info.
 // If t is a type parameter, the result is true if isBasic(t, info) is true
 // for all specific types of the type parameter's type set.
-// allBasic(t, info) is an optimized version of isBasic(structuralType(t), info).
+// allBasic(t, info) is an optimized version of isBasic(coreType(t), info).
 func allBasic(t Type, info BasicInfo) bool {
 	if tpar, _ := t.(*TypeParam); tpar != nil {
 		return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) })

src/go/types/stmt.go

@@ -418,9 +418,9 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		if ch.mode == invalid || val.mode == invalid {
 			return
 		}
-		u := structuralType(ch.typ)
+		u := coreType(ch.typ)
 		if u == nil {
-			check.invalidOp(inNode(s, s.Arrow), _InvalidSend, "cannot send to %s: no structural type", &ch)
+			check.invalidOp(inNode(s, s.Arrow), _InvalidSend, "cannot send to %s: no core type", &ch)
 			return
 		}
 		uch, _ := u.(*Chan)
@@ -831,12 +831,12 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		// determine key/value types
 		var key, val Type
 		if x.mode != invalid {
-			// Ranging over a type parameter is permitted if it has a structural type.
+			// Ranging over a type parameter is permitted if it has a core type.
 			var cause string
-			u := structuralType(x.typ)
+			u := coreType(x.typ)
 			switch t := u.(type) {
 			case nil:
-				cause = check.sprintf("%s has no structural type", x.typ)
+				cause = check.sprintf("%s has no core type", x.typ)
 			case *Chan:
 				if s.Value != nil {
 					check.softErrorf(s.Value, _InvalidIterVar, "range over %s permits only one iteration variable", &x)

src/go/types/testdata/check/builtins.go2

@@ -148,7 +148,7 @@ func _[
 	_ = 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 S2: no structural type */ , 10)
+	_ = make(S2 /* ERROR cannot make S2: no core type */ , 10)
 
 	type M0 map[string]int
 	_ = make(map[string]int)
@@ -156,7 +156,7 @@ func _[
 	_ = make(M1)
 	_ = make(M1, 10)
 	_ = make/* ERROR expects 1 or 2 arguments */(M1, 10, 20)
-	_ = make(M2 /* ERROR cannot make M2: no structural type */ )
+	_ = make(M2 /* ERROR cannot make M2: no core type */ )
 
 	type C0 chan int
 	_ = make(chan int)
@@ -164,7 +164,7 @@ func _[
 	_ = make(C1)
 	_ = make(C1, 10)
 	_ = make/* ERROR expects 1 or 2 arguments */(C1, 10, 20)
-	_ = make(C2 /* ERROR cannot make C2: no structural type */ )
+	_ = make(C2 /* ERROR cannot make C2: no core type */ )
 	_ = make(C3)
 }
 

src/go/types/testdata/check/typeparams.go2

@@ -134,11 +134,11 @@ func _[T interface{ ~string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3
 type myByte1 []byte
 type myByte2 []byte
 func _[T interface{ []byte | myByte1 | myByte2 }] (x T, i, j, k int) { var _ T = x[i:j:k] }
-func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x /* ERROR no structural type */ [i:j:k] }
+func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x /* ERROR no core type */ [i:j:k] }
 
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j] }
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3-index slice of string */ ] }
-func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x /* ERROR no structural type */ [i:j] }
+func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x /* ERROR no core type */ [i:j] }
 
 // len/cap built-ins
 
@@ -230,7 +230,7 @@ func _[
         for _, _ = range s1 {}
 
         var s2 S2
-        for range s2 /* ERROR cannot range over s2.*no structural type */ {}
+        for range s2 /* ERROR cannot range over s2.*no core type */ {}
 
         var a0 []int
         for range a0 {}
@@ -243,7 +243,7 @@ func _[
         for _, _ = range a1 {}
 
         var a2 A2
-        for range a2 /* ERROR cannot range over a2.*no structural type */ {}
+        for range a2 /* ERROR cannot range over a2.*no core type */ {}
 
         var p0 *[10]int
         for range p0 {}
@@ -256,7 +256,7 @@ func _[
         for _, _ = range p1 {}
 
         var p2 P2
-        for range p2 /* ERROR cannot range over p2.*no structural type */ {}
+        for range p2 /* ERROR cannot range over p2.*no core type */ {}
 
         var m0 map[string]int
         for range m0 {}
@@ -269,7 +269,7 @@ func _[
         for _, _ = range m1 {}
 
         var m2 M2
-        for range m2 /* ERROR cannot range over m2.*no structural type */ {}
+        for range m2 /* ERROR cannot range over m2.*no core type */ {}
 }
 
 // type inference checks

src/go/types/testdata/examples/inference.go2

@@ -113,7 +113,7 @@ func _() {
 	// from the first one through constraint type inference.
 	related3[int]()
 
-	// The inferred type is the structural type of the Slice
+	// The inferred type is the core type of the Slice
 	// type parameter.
 	var _ []int = related3[int]()
 

src/go/types/testdata/examples/types.go2

@@ -298,7 +298,7 @@ func _[T interface {~int|~float64}]() {
 
 // It is possible to create composite literals of type parameter
 // type as long as it's possible to create a composite literal
-// of the structural type of the type parameter's constraint.
+// of the core type of the type parameter's constraint.
 func _[P interface{ ~[]int }]() P {
 	return P{}
 	return P{1, 2, 3}
@@ -313,7 +313,7 @@ func _[P interface{ ~[]E }, E interface{ map[string]P } ]() P {
 }
 
 // This is a degenerate case with a singleton type set, but we can create
-// composite literals even if the structural type is a defined type.
+// composite literals even if the core type is a defined type.
 type MyInts []int
 
 func _[P MyInts]() P {

src/go/types/testdata/fixedbugs/issue43671.go2

@@ -12,7 +12,7 @@ type C4 interface{ chan int | chan<- int }
 type C5[T any] interface{ ~chan T | <-chan T }
 
 func _[T any](ch T) {
-	<-ch // ERROR cannot receive from ch .* no structural type
+	<-ch // ERROR cannot receive from ch .* no core type
 }
 
 func _[T C0](ch T) {
@@ -28,7 +28,7 @@ func _[T C2](ch T) {
 }
 
 func _[T C3](ch T) {
-	<-ch // ERROR cannot receive from ch .* no structural type
+	<-ch // ERROR cannot receive from ch .* no core type
 }
 
 func _[T C4](ch T) {

src/go/types/testdata/fixedbugs/issue47115.go2

@@ -12,7 +12,7 @@ type C4 interface{ chan int | chan<- int }
 type C5[T any] interface{ ~chan T | chan<- T }
 
 func _[T any](ch T) {
-	ch <- /* ERROR cannot send to ch .* no structural type */ 0
+	ch <- /* ERROR cannot send to ch .* no core type */ 0
 }
 
 func _[T C0](ch T) {
@@ -28,7 +28,7 @@ func _[T C2](ch T) {
 }
 
 func _[T C3](ch T) {
-	ch <- /* ERROR cannot send to ch .* no structural type */ 0
+	ch <- /* ERROR cannot send to ch .* no core type */ 0
 }
 
 func _[T C4](ch T) {

src/go/types/testdata/fixedbugs/issue49735.go2

@@ -6,6 +6,6 @@ package p
 
 func _[P1 any, P2 ~byte](s1 P1, s2 P2) {
         _ = append(nil /* ERROR first argument to append must be a slice; have untyped nil */ , 0)
-        _ = append(s1 /* ERROR s1 .* has no structural type */ , 0)
+        _ = append(s1 /* ERROR s1 .* has no core type */ , 0)
-        _ = append(s2 /* ERROR s2 .* has structural type byte */ , 0)
+        _ = append(s2 /* ERROR s2 .* has core type byte */ , 0)
 }

src/go/types/testdata/fixedbugs/issue50417.go2

@@ -51,7 +51,7 @@ func f2[P interface{ Sfm; m() }](p P) {
 
 var _ = f2[Sfm]
 
-// special case: structural type is a named pointer type
+// special case: core type is a named pointer type
 
 type PSfm *Sfm
 

src/go/types/type.go

@@ -27,13 +27,13 @@ func under(t Type) Type {
 	return t.Underlying()
 }
 
-// If t is not a type parameter, structuralType returns the underlying type.
+// If t is not a type parameter, coreType returns the underlying type.
-// If t is a type parameter, structuralType returns the single underlying
+// If t is a type parameter, coreType returns the single underlying
 // type of all types in its type set if it exists, or nil otherwise. If the
 // type set contains only unrestricted and restricted channel types (with
 // identical element types), the single underlying type is the restricted
 // channel type if the restrictions are always the same, or nil otherwise.
-func structuralType(t Type) Type {
+func coreType(t Type) Type {
 	tpar, _ := t.(*TypeParam)
 	if tpar == nil {
 		return under(t)
@@ -59,10 +59,10 @@ func structuralType(t Type) Type {
 	return nil
 }
 
-// structuralString is like structuralType but also considers []byte
+// coreString is like coreType but also considers []byte
 // and strings as identical. In this case, if successful and we saw
 // a string, the result is of type (possibly untyped) string.
-func structuralString(t Type) Type {
+func coreString(t Type) Type {
 	tpar, _ := t.(*TypeParam)
 	if tpar == nil {
 		return under(t) // string or untyped string

test/typeparam/issue50417.go

@@ -57,7 +57,7 @@ func f2[P interface {
 
 var _ = f2[Sfm]
 
-// special case: structural type is a named pointer type
+// special case: core type is a named pointer type
 
 type PSfm *Sfm
 
@@ -68,7 +68,7 @@ func f3[P interface{ PSfm }](p P) {
 
 var _ = f3[PSfm]
 
-// special case: structural type is an unnamed pointer type
+// special case: core type is an unnamed pointer type
 
 func f4[P interface{ *Sfm }](p P) {
 	_ = p.f

test/typeparam/typelist.go

@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This file tests type lists & structural constraints.
+// This file tests type lists & constraints with core types.
 
 // Note: This test has been adjusted to use the new
 //       type set notation rather than type lists.
@@ -30,28 +30,28 @@ func _[T interface{ ~int }](x T) {
 	var _ T = 42
 	var _ T = T(myint(42))
 }
+
 // TODO: put this type declaration back inside the above function when issue 47631 is fixed.
 type myint int
 
-// Indexing a generic type which has a structural contraints to be an array.
+// Indexing a generic type which has a an array as core type.
 func _[T interface{ ~[10]int }](x T) {
 	_ = x[9] // ok
 }
 
-// Dereference of a generic type which has a structural contraint to be a pointer.
+// Dereference of a generic type which has a pointer as core type.
 func _[T interface{ ~*int }](p T) int {
 	return *p
 }
 
-// Channel send and receive on a generic type which has a structural constraint to
+// Channel send and receive on a generic type which has a channel as core type.
-// be a channel.
 func _[T interface{ ~chan int }](ch T) int {
 	// This would deadlock if executed (but ok for a compile test)
 	ch <- 0
 	return <-ch
 }
 
-// Calling of a generic type which has a structural constraint to be a function.
+// Calling of a generic type which has a function as core type.
 func _[T interface{ ~func() }](f T) {
 	f()
 	go f()
@@ -62,7 +62,7 @@ func _[T interface{ ~func(string) int }](f T) int {
 	return f("hello")
 }
 
-// Map access of a generic type which has a structural constraint to be a map.
+// Map access of a generic type which has a map as core type.
 func _[V any, T interface{ ~map[string]V }](p T) V {
 	return p["test"]
 }
@@ -122,7 +122,9 @@ func f5[A interface {
 		b B
 		c C
 	}
-}, B any, C interface{ ~*B }](x B) A { panic(0) }
+}, B any, C interface{ ~*B }](x B) A {
+	panic(0)
+}
 func f5x() {
 	x := f5(1.2)
 	var _ float64 = x.b