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 <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: griesemer

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

@@ -82,18 +82,18 @@ 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
 			switch {
 			case x.isNil():
 				cause = "have untyped nil"
 			case isTypeParam(S):
-				if u := structuralType(S); u != nil {
-					cause = check.sprintf("%s has structural type %s", x, u)
+				if u := coreType(S); u != nil {
+					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.
-func StructuralType(t Type) Type {
-	return structuralType(t)
+// If typ is not a type parameter, CoreType returns the underlying type.
+func CoreType(t Type) Type {
+	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
 		}
@@ -1359,15 +1359,15 @@ 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
 			check.error(e, "missing type in composite literal")
 			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
-	// don't have any type arguments to fill in for *P or Q (issue #45548).
+	// e.g., a constraint with core type *P may match a type parameter Q but
+	// 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,
-	// see if there is a matching field (but not a method, those need to be declared explicitly
-	// in the constraint). If the structural constraint is a named pointer type (see above), we
-	// are ok here because only fields are accepted as results.
+	// 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 in the constraint). If the constraint is a named pointer type (see
+	// 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) })