cmd/compile: get rid of Fields in types.Interface, use allMethods in types.Type instead

Confusingly, the set of all methods of an interface is currently set in
Fields field of types.Interface. This is true, even though there is
already an allMethods field (and AllMethods method) of types.Type.
Change so the set of all methods of an interface are stored in
Type.allMethods, and Interface.Fields is removed. Update the comments
for Methods and AllMethods.

Change-Id: Ibc32bafae86831cba62606b079a855690612c759
Reviewed-on: https://go-review.googlesource.com/c/go/+/307209
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 29 insertions, 20 deletions

diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index 762cdd3258..969195b850 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -368,8 +368,7 @@ func (t *Type) StructType() *Struct {
 
 // Interface contains Type fields specific to interface types.
 type Interface struct {
-	Fields Fields
-	pkg    *Pkg
+	pkg *Pkg
 }
 
 // Ptr contains Type fields specific to pointer types.
@@ -922,40 +921,49 @@ func (t *Type) IsFuncArgStruct() bool {
 	return t.kind == TSTRUCT && t.Extra.(*Struct).Funarg != FunargNone
 }
 
+// Methods returns a pointer to the base methods (excluding embedding) for type t.
+// These can either be concrete methods (for non-interface types) or interface
+// methods (for interface types).
 func (t *Type) Methods() *Fields {
-	// TODO(mdempsky): Validate t?
 	return &t.methods
 }
 
+// AllMethods returns a pointer to all the methods (including embedding) for type t.
+// For an interface type, this is the set of methods that are typically iterated over.
 func (t *Type) AllMethods() *Fields {
-	// TODO(mdempsky): Validate t?
+	if t.kind == TINTER {
+		// Calculate the full method set of an interface type on the fly
+		// now, if not done yet.
+		CalcSize(t)
+	}
 	return &t.allMethods
 }
 
+// SetAllMethods sets the set of all methods (including embedding) for type t.
+// Use this method instead of t.AllMethods().Set(), which might call CalcSize() on
+// an uninitialized interface type.
+func (t *Type) SetAllMethods(fs []*Field) {
+	t.allMethods.Set(fs)
+}
+
+// Fields returns the fields of struct type t.
 func (t *Type) Fields() *Fields {
-	switch t.kind {
-	case TSTRUCT:
-		return &t.Extra.(*Struct).fields
-	case TINTER:
-		CalcSize(t)
-		return &t.Extra.(*Interface).Fields
-	}
-	base.Fatalf("Fields: type %v does not have fields", t)
-	return nil
+	t.wantEtype(TSTRUCT)
+	return &t.Extra.(*Struct).fields
 }
 
-// Field returns the i'th field/method of struct/interface type t.
+// Field returns the i'th field of struct type t.
 func (t *Type) Field(i int) *Field {
 	return t.Fields().Slice()[i]
 }
 
-// FieldSlice returns a slice of containing all fields/methods of
-// struct/interface type t.
+// FieldSlice returns a slice of containing all fields of
+// a struct type t.
 func (t *Type) FieldSlice() []*Field {
 	return t.Fields().Slice()
 }
 
-// SetFields sets struct/interface type t's fields/methods to fields.
+// SetFields sets struct type t's fields to fields.
 func (t *Type) SetFields(fields []*Field) {
 	// If we've calculated the width of t before,
 	// then some other type such as a function signature
@@ -981,6 +989,7 @@ func (t *Type) SetFields(fields []*Field) {
 	t.Fields().Set(fields)
 }
 
+// SetInterface sets the base methods of an interface type t.
 func (t *Type) SetInterface(methods []*Field) {
 	t.wantEtype(TINTER)
 	t.Methods().Set(methods)
@@ -1231,8 +1240,8 @@ func (t *Type) cmp(x *Type) Cmp {
 		return CMPeq
 
 	case TINTER:
-		tfs := t.FieldSlice()
-		xfs := x.FieldSlice()
+		tfs := t.AllMethods().Slice()
+		xfs := x.AllMethods().Slice()
 		for i := 0; i < len(tfs) && i < len(xfs); i++ {
 			t1, x1 := tfs[i], xfs[i]
 			if c := t1.Sym.cmpsym(x1.Sym); c != CMPeq {
@@ -1420,7 +1429,7 @@ func (t *Type) IsInterface() bool {
 
 // IsEmptyInterface reports whether t is an empty interface type.
 func (t *Type) IsEmptyInterface() bool {
-	return t.IsInterface() && t.NumFields() == 0
+	return t.IsInterface() && t.AllMethods().Len() == 0
 }
 
 // IsScalar reports whether 't' is a scalar Go type, e.g.