cmd/compile/internal/types2: minor cleanups in predicates.go

- reordered some functions for better organization
- renamed single arguments typ to t for consistency
- updated some comments

No functional changes.

Change-Id: I4362ac48044595cdf5c3d9eb7b2f7b94e776d65b
Reviewed-on: https://go-review.googlesource.com/c/go/+/360956
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

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

@@ -6,25 +6,6 @@
 
 package types2
 
-// hasName reports whether typ has a name. This includes
-// predeclared types, defined types, and type parameters.
-// hasName may be called with types that are not fully set up.
-func hasName(typ Type) bool {
-	switch typ.(type) {
-	case *Basic, *Named, *TypeParam:
-		return true
-	}
-	return false
-}
-
-// isGeneric reports whether a type is a generic, uninstantiated type (generic
-// signatures are not included).
-func isGeneric(typ Type) bool {
-	// A parameterized type is only instantiated if it doesn't have an instantiation already.
-	named, _ := typ.(*Named)
-	return named != nil && named.obj != nil && named.targs == nil && named.TypeParams() != nil
-}
-
 // The isX predicates below report whether t is an X.
 // If t is a type parameter the result is false; i.e.,
 // these predicates don't look inside a type parameter.
@@ -37,6 +18,7 @@ func isComplex(t Type) bool        { return isBasic(t, IsComplex) }
 func isNumeric(t Type) bool        { return isBasic(t, IsNumeric) }
 func isString(t Type) bool         { return isBasic(t, IsString) }
 func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) }
+func isConstType(t Type) bool      { return isBasic(t, IsConstType) }
 
 // isBasic reports whether under(t) is a basic type with the specified info.
 // If t is a type parameter the result is false; i.e.,
@@ -74,38 +56,52 @@ func allBasic(t Type, info BasicInfo) bool {
 	return false
 }
 
-// isTyped reports whether typ is typed; i.e., not an untyped
+// hasName reports whether t has a name. This includes
+// predeclared types, defined types, and type parameters.
+// hasName may be called with types that are not fully set up.
+func hasName(t Type) bool {
+	switch t.(type) {
+	case *Basic, *Named, *TypeParam:
+		return true
+	}
+	return false
+}
+
+// isTyped reports whether t is typed; i.e., not an untyped
 // constant or boolean. isTyped may be called with types that
 // are not fully set up.
-func isTyped(typ Type) bool {
+func isTyped(t Type) bool {
 	// isTyped is called with types that are not fully
 	// set up. Must not call asBasic()!
-	t, _ := typ.(*Basic)
-	return t == nil || t.info&IsUntyped == 0
+	b, _ := t.(*Basic)
+	return b == nil || b.info&IsUntyped == 0
 }
 
-// isUntyped(typ) is the same as !isTyped(typ).
-func isUntyped(typ Type) bool {
-	return !isTyped(typ)
+// isUntyped(t) is the same as !isTyped(t).
+func isUntyped(t Type) bool {
+	return !isTyped(t)
 }
 
-func isConstType(typ Type) bool {
-	// Type parameters are never const types.
-	t := asBasic(typ)
-	return t != nil && t.info&IsConstType != 0
+// IsInterface reports whether t is an interface type.
+func IsInterface(t Type) bool {
+	return asInterface(t) != nil
 }
 
-// IsInterface reports whether typ is an interface type.
-func IsInterface(typ Type) bool {
-	return asInterface(typ) != nil
-}
-
-// isTypeParam reports whether typ is a type parameter.
-func isTypeParam(typ Type) bool {
-	_, ok := under(typ).(*TypeParam)
+// isTypeParam reports whether t is a type parameter.
+func isTypeParam(t Type) bool {
+	_, ok := under(t).(*TypeParam)
 	return ok
 }
 
+// isGeneric reports whether a type is a generic, uninstantiated type
+// (generic signatures are not included).
+// TODO(gri) should we include signatures or assert that they are not present?
+func isGeneric(t Type) bool {
+	// A parameterized type is only generic if it doesn't have an instantiation already.
+	named, _ := t.(*Named)
+	return named != nil && named.obj != nil && named.targs == nil && named.TypeParams() != nil
+}
+
 // Comparable reports whether values of type T are comparable.
 func Comparable(T Type) bool {
 	return comparable(T, nil)
@@ -142,15 +138,15 @@ func comparable(T Type, seen map[Type]bool) bool {
 	return false
 }
 
-// hasNil reports whether a type includes the nil value.
-func hasNil(typ Type) bool {
-	switch t := under(typ).(type) {
+// hasNil reports whether type t includes the nil value.
+func hasNil(t Type) bool {
+	switch u := under(t).(type) {
 	case *Basic:
-		return t.kind == UnsafePointer
+		return u.kind == UnsafePointer
 	case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan:
 		return true
 	case *TypeParam:
-		return t.underIs(hasNil)
+		return u.underIs(hasNil)
 	}
 	return false
 }
@@ -392,9 +388,8 @@ func identicalTParams(x, y []*TypeParam, cmpTags bool, p *ifacePair) bool {
 // Default returns the default "typed" type for an "untyped" type;
 // it returns the incoming type for all other types. The default type
 // for untyped nil is untyped nil.
-//
-func Default(typ Type) Type {
-	if t, ok := typ.(*Basic); ok {
+func Default(t Type) Type {
+	if t, ok := t.(*Basic); ok {
 		switch t.kind {
 		case UntypedBool:
 			return Typ[Bool]
@@ -410,5 +405,5 @@ func Default(typ Type) Type {
 			return Typ[String]
 		}
 	}
-	return typ
+	return t
 }