go.tools/ssa: (another) major refactoring of method-set logic.

We now use LookupFieldOrMethod for all SelectorExprs, and
simplify the logic to discriminate the various cases.

We inline static calls to promoted/indirected functions,
dramatically reducing the number of functions created.

More tests are needed, but I'd like to submit this as-is.

In this CL, we:
- rely less on Id strings.  Internally we now use
  *types.Method (and its components) almost everywhere.
- stop thinking of types.Methods as objects. They don't
  have stable identities. (Hopefully they will become
  plain-old structs soon.)
- eliminate receiver indirection wrappers:
  indirection and promotion are handled together by makeWrapper.
- Handle the interactions of promotion, indirection and
  abstract methods much more cleanly.
- support receiver-bound interface method closures.
- break up builder.selectField so we can re-use parts
  (emitFieldSelection).
- add importer.PackageInfo.classifySelector utility.
- delete interfaceMethodIndex()
- delete namedTypeMethodIndex()
- delete isSuperInterface() (replaced by types.IsAssignable)
- call memberFromObject on each declared concrete method's
  *types.Func, not on every Method frem each method set, in the
  CREATE phase for packages loaded by gcimporter.

go/types:
- document Func, Signature.Recv() better.
- use fmt in {Package,Label}.String
- reimplement Func.String to be prettier and to include method
  receivers.

API changes:
- Function.method now holds the types.Method (soon to be
  not-an-object) for synthetic wrappers.
- CallCommon.Method now contains an abstract (interface)
  method object; was an abstract method index.
- CallCommon.MethodId() gone.
- Program.LookupMethod now takes a *Method not an Id string.

R=gri
CC=golang-dev
https://golang.org/cl/11674043

go/types/methodset.go

@@ -23,6 +23,12 @@ type Method struct {
 	selectorPath
 }
 
+// TODO(gri): expose this or something like it (e.g. lookupResult) to
+// make life easier for callers of LookupFieldOrMethod.
+func NewMethod(f *Func, recv Type, index []int, indirect bool) *Method {
+	return &Method{f, selectorPath{recv, index, indirect}}
+}
+
 // Type returns the promoted signature type of m (i.e., the receiver
 // type is Recv()).
 func (m *Method) Type() Type {
@@ -33,6 +39,10 @@ func (m *Method) Type() Type {
 	return &sig
 }
 
+func (m *Method) String() string {
+	return fmt.Sprintf("method (%s).%s %s", m.Recv(), m.Name(), m.Type())
+}
+
 // A selectorPath describes the path from a value x to one of its fields
 // or methods f for a selector expression x.f. A path may include implicit
 // field selections (e.g., x.f may be x.a.b.c.f).

go/types/objects.go

@@ -6,6 +6,7 @@ package types
 
 import (
 	"bytes"
+	"fmt"
 	"go/ast"
 	"go/token"
 
@@ -46,6 +47,10 @@ func Id(pkg *Package, name string) string {
 	}
 	// unexported names need the package path for differentiation
 	path := ""
+	// TODO(gri): shouldn't !ast.IsExported(name) => pkg != nil be an precondition?
+	// if pkg == nil {
+	// 	panic("nil package in lookup of unexported name")
+	// }
 	if pkg != nil {
 		path = pkg.path
 		if path == "" {
@@ -82,8 +87,10 @@ func (obj *object) toString(kind string, typ Type) string {
 		buf.WriteByte('.')
 	}
 	buf.WriteString(obj.name)
+	if typ != nil {
 		buf.WriteByte(' ')
 		writeType(&buf, typ)
+	}
 
 	return buf.String()
 }
@@ -127,7 +134,7 @@ func NewPackage(pos token.Pos, path, name string, scope *Scope, imports map[stri
 	return obj
 }
 
-func (obj *Package) String() string               { return obj.toString("package", nil) }
+func (obj *Package) String() string               { return fmt.Sprintf("package %s", obj.Path()) }
 func (obj *Package) Path() string                 { return obj.path }
 func (obj *Package) Scope() *Scope                { return obj.scope }
 func (obj *Package) Imports() map[string]*Package { return obj.imports }
@@ -178,7 +185,9 @@ func NewFieldVar(pos token.Pos, pkg *Package, name string, typ Type, anonymous b
 func (obj *Var) Anonymous() bool { return obj.anonymous }
 func (obj *Var) String() string  { return obj.toString("var", obj.typ) }
 
-// A Func represents a declared function.
+// A Func represents a declared function, concrete method, or abstract
+// (interface) method.  Its Type() is a *Signature.
+// An abstract method may belong to many interfaces due to embedding.
 type Func struct {
 	object
 }
@@ -187,7 +196,33 @@ func NewFunc(pos token.Pos, pkg *Package, name string, typ Type) *Func {
 	return &Func{object{nil, pos, pkg, name, typ}}
 }
 
-func (obj *Func) String() string { return obj.toString("func", obj.typ) }
+func (obj *Func) String() string {
+	var buf bytes.Buffer
+
+	buf.WriteString("func ")
+	sig := obj.typ.(*Signature)
+	if recv := sig.Recv(); recv != nil {
+		buf.WriteByte('(')
+		if _, ok := recv.Type().(*Interface); ok {
+			// gcimporter creates abstract methods of
+			// named interfaces using the interface type
+			// (not the named type) as the receiver.
+			// Don't print it in full.
+			buf.WriteString("interface")
+		} else {
+			writeType(&buf, recv.Type())
+		}
+		buf.WriteByte(')')
+		buf.WriteByte(' ')
+	}
+	if obj.pkg != nil {
+		buf.WriteString(obj.pkg.name)
+		buf.WriteByte('.')
+	}
+	buf.WriteString(obj.name)
+	writeSignature(&buf, sig)
+	return buf.String()
+}
 
 // A Label represents a declared label.
 type Label struct {
@@ -198,4 +233,4 @@ func NewLabel(pos token.Pos, name string) *Label {
 	return &Label{object{nil, pos, nil, name, nil}}
 }
 
-func (obj *Label) String() string { return obj.toString("label", nil) }
+func (obj *Label) String() string { return fmt.Sprintf("label %s", obj.Name()) }

go/types/types.go

@@ -191,7 +191,7 @@ func (t *Tuple) Len() int {
 // At returns the i'th variable of tuple t.
 func (t *Tuple) At(i int) *Var { return t.vars[i] }
 
-// A Signature represents a (non-builtin) function type.
+// A Signature represents a (non-builtin) function or method type.
 type Signature struct {
 	scope      *Scope // function scope, always present
 	labels     *Scope // label scope, or nil (lazily allocated)
@@ -220,7 +220,12 @@ func NewSignature(scope *Scope, recv *Var, params, results *Tuple, isVariadic bo
 	return &Signature{scope, nil, recv, params, results, isVariadic}
 }
 
-// Recv returns the receiver of signature s, or nil.
+// Recv returns the receiver of signature s (if a method), or nil if a
+// function.
+//
+// For an abstract method, Recv returns the enclosing interface either
+// as a *Named or an *Interface.  Due to embedding, an interface may
+// contain methods whose receiver type is a different interface.
 func (s *Signature) Recv() *Var { return s.recv }
 
 // Params returns the parameters of signature s, or nil.

importer/pkginfo.go

@@ -122,6 +122,26 @@ func (info *PackageInfo) IsPackageRef(sel *ast.SelectorExpr) types.Object {
 	return nil
 }
 
+// ClassifySelector returns one of token.{PACKAGE,VAR,TYPE} to
+// indicate whether the base operand of sel is a package, expression
+// or type, respectively.
+//
+// Examples:
+// PACKAGE: fmt.Println (func), math.Pi (const), types.Universe (var)
+// VAR:     info.IsType (*Method), info.Objects (*Field)
+// TYPE:    PackageInfo.IsType (func)
+//
+func (info *PackageInfo) ClassifySelector(sel *ast.SelectorExpr) token.Token {
+	switch {
+	case info.IsPackageRef(sel) != nil:
+		return token.PACKAGE
+	case info.IsType(sel.X):
+		return token.TYPE
+	default:
+		return token.VAR
+	}
+}
+
 // TypeCaseVar returns the implicit variable created by a single-type
 // case clause in a type switch, or nil if not found.
 //

ssa/builder.go

@@ -19,8 +19,8 @@ package ssa
 //
 // The builder's and Program's indices (maps) are populated and
 // mutated during the CREATE phase, but during the BUILD phase they
-// remain constant.  The sole exception is Prog.methodSets, which is
-// protected by a dedicated mutex.
+// remain constant.  The sole exception is Prog.methodSets and its
+// related maps, which are protected by a dedicated mutex.
 
 import (
 	"fmt"
@@ -328,64 +328,6 @@ func (b *builder) builtin(fn *Function, name string, args []ast.Expr, typ types.
 	return nil // treat all others as a regular function call
 }
 
-// selectField evaluates the field selector expression e and returns its value,
-// or if wantAddr is true, its address, in which case escaping
-// indicates whether the caller intends to use the resulting pointer
-// in a potentially escaping way.
-//
-func (b *builder) selectField(fn *Function, e *ast.SelectorExpr, wantAddr, escaping bool) Value {
-	tx := fn.Pkg.typeOf(e.X)
-	obj, indices, isIndirect := types.LookupFieldOrMethod(tx, fn.Pkg.Object, e.Sel.Name)
-	if obj == nil {
-		panic("field not found: " + e.Sel.Name)
-	}
-
-	// Be careful!  This code has proven very tricky.
-
-	// NB: The type of the final field is irrelevant to the logic.
-
-	// Emit code for the base expression.
-	var v Value
-	if wantAddr && !isIndirect && !isPointer(tx) {
-		// TODO(adonovan): opt: also use this codepath
-		// for !wantAddr, when safe (i.e. e.X is addressible),
-		// since (FieldAddr;Load) is cheaper than (Load;Field).
-		// Requires go/types to expose addressibility.
-		v = b.addr(fn, e.X, escaping).address(fn)
-	} else {
-		v = b.expr(fn, e.X)
-	}
-
-	v = emitImplicitSelections(fn, v, indices[:len(indices)-1])
-
-	// Final explicit field selection.
-	// Invariant: v.Type() is a possibly named struct or *struct.
-	index := indices[len(indices)-1]
-	fld := deref(v.Type()).Underlying().(*types.Struct).Field(index)
-	if isPointer(v.Type()) {
-		instr := &FieldAddr{
-			X:     v,
-			Field: index,
-		}
-		instr.setPos(e.Sel.Pos())
-		instr.setType(types.NewPointer(fld.Type()))
-		v = fn.emit(instr)
-		// Load the field's value iff we don't want its address.
-		if !wantAddr {
-			v = emitLoad(fn, v)
-		}
-	} else {
-		instr := &Field{
-			X:     v,
-			Field: index,
-		}
-		instr.setPos(e.Sel.Pos())
-		instr.setType(fld.Type())
-		v = fn.emit(instr)
-	}
-	return v
-}
-
 // addr lowers a single-result addressable expression e to SSA form,
 // emitting code to fn and returning the location (an lvalue) defined
 // by the expression.
@@ -445,8 +387,15 @@ func (b *builder) addr(fn *Function, e ast.Expr, escaping bool) lvalue {
 			panic("undefined package-qualified name: " + obj.Name())
 		}
 
-		// e.f where e is an expression.
-		return &address{addr: b.selectField(fn, e, true, escaping)}
+		// e.f where e is an expression and f is a field.
+		typ := fn.Pkg.typeOf(e.X)
+		obj, indices, isIndirect := types.LookupFieldOrMethod(typ, fn.Pkg.Object, e.Sel.Name)
+		_ = obj.(*types.Var) // assertion
+
+		wantAddr := true
+		v := b.receiver(fn, e.X, wantAddr, escaping, indices, isIndirect)
+		last := len(indices) - 1
+		return &address{addr: emitFieldSelection(fn, v, indices[last], true, e.Sel.Pos())}
 
 	case *ast.IndexExpr:
 		var x Value
@@ -676,37 +625,66 @@ func (b *builder) expr(fn *Function, e ast.Expr) Value {
 		return v
 
 	case *ast.SelectorExpr:
+		selKind := fn.Pkg.info.ClassifySelector(e)
+
 		// p.M where p is a package.
-		if obj := fn.Pkg.info.IsPackageRef(e); obj != nil {
+		if selKind == token.PACKAGE {
 			return b.expr(fn, e.Sel)
 		}
 
-		id := types.Id(fn.Pkg.Object, e.Sel.Name)
+		typ := fn.Pkg.typeOf(e.X)
+		obj, indices, isIndirect := types.LookupFieldOrMethod(typ, fn.Pkg.Object, e.Sel.Name)
 
 		// (*T).f or T.f, the method f from the method-set of type T.
-		if fn.Pkg.info.IsType(e.X) {
-			typ := fn.Pkg.typeOf(e.X)
-			if m := fn.Prog.LookupMethod(typ, id); m != nil {
-				return emitConv(fn, m, fn.Pkg.typeOf(e))
+		// We return a standalone function that calls the method.
+		if selKind == token.TYPE {
+			obj := obj.(*types.Func)
+			if _, ok := typ.Underlying().(*types.Interface); ok {
+				// T is an interface; return wrapper.
+				fn.Prog.methodsMu.Lock()
+				defer fn.Prog.methodsMu.Unlock()
+				return interfaceMethodWrapper(fn.Prog, typ, obj)
 			}
 
-			// T must be an interface; return wrapper.
-			return interfaceMethodWrapper(fn.Prog, typ, id)
+			// TODO(gri): make LookupFieldOrMethod return one of these
+			// so we don't have to construct it.
+			meth := types.NewMethod(obj, typ, indices, isIndirect)
+			// For declared methods, a simple conversion will suffice.
+			return emitConv(fn, fn.Prog.LookupMethod(meth), fn.Pkg.typeOf(e))
 		}
 
-		// Bound method closure?  (e.m where m is a method)
-		if m, recv := b.findMethod(fn, e.X, id); m != nil {
+		// selKind == token.VAR
+
+		switch obj := obj.(type) {
+		case *types.Func:
+			// e.f where e is an expression and f is a method.
+			// The result is a bound method closure.
+			wantAddr := isPointer(recvType(obj))
+			escaping := true
+			v := b.receiver(fn, e.X, wantAddr, escaping, indices, isIndirect)
+			// TODO(adonovan): test the case where
+			// *struct{I} inherits a method from interface I.
 			c := &MakeClosure{
-				Fn:       boundMethodWrapper(m),
-				Bindings: []Value{recv},
+				Fn:       boundMethodWrapper(fn.Prog, obj),
+				Bindings: []Value{v},
 			}
 			c.setPos(e.Sel.Pos())
 			c.setType(fn.Pkg.typeOf(e))
 			return fn.emit(c)
+
+			// TODO(adonovan): add more tests for
+			// interaction of bound interface method
+			// closures and promotion.
+
+		case *types.Var:
+			// e.f where e is an expression and f is a field.
+			last := len(indices) - 1
+			v := b.expr(fn, e.X)
+			v = emitImplicitSelections(fn, v, indices[:last])
+			return emitFieldSelection(fn, v, indices[last], false, e.Sel.Pos())
 		}
 
-		// e.f where e is an expression.  f may be a method.
-		return b.selectField(fn, e, false, false)
+		panic("unexpected expression-relative selector")
 
 	case *ast.IndexExpr:
 		switch t := fn.Pkg.typeOf(e.X).Underlying().(type) {
@@ -763,39 +741,27 @@ func (b *builder) stmtList(fn *Function, list []ast.Stmt) {
 	}
 }
 
-// findMethod returns the method and receiver for a call base.id().
-// It locates the method using the method-set for base's type,
-// and emits code for the receiver, handling the cases where
-// the formal and actual parameter's pointerness are unequal.
+// receiver emits to fn code for expression e in the "receiver"
+// position of selection e.f (where f may be a field or a method) and
+// returns the effective receiver after applying the implicit field
+// selections of indices (the last element of which is ignored).
 //
-// findMethod returns (nil, nil) if no such method was found.
+// wantAddr requests that the result is an an address.  If
+// !isIndirect, this may require that e be build in addr() mode; it
+// must thus be addressable.
 //
-func (b *builder) findMethod(fn *Function, base ast.Expr, id string) (*Function, Value) {
-	typ := fn.Pkg.typeOf(base)
+// escaping is defined as per builder.addr().
+//
+func (b *builder) receiver(fn *Function, e ast.Expr, wantAddr, escaping bool, indices []int, isIndirect bool) Value {
+	var v Value
+	if wantAddr && !isIndirect && !isPointer(fn.Pkg.typeOf(e)) {
+		v = b.addr(fn, e, escaping).address(fn)
+	} else {
+		v = b.expr(fn, e)
+	}
 
-	// Consult method-set of X.
-	if m := fn.Prog.LookupMethod(typ, id); m != nil {
-		aptr := isPointer(typ)
-		fptr := isPointer(m.Signature.Recv().Type())
-		if aptr == fptr {
-			// Actual's and formal's "pointerness" match.
-			return m, b.expr(fn, base)
-		}
-		// Actual is a pointer, formal is not.
-		// Load a copy.
-		return m, emitLoad(fn, b.expr(fn, base))
-	}
-	if !isPointer(typ) {
-		// Consult method-set of *X.
-		if m := fn.Prog.LookupMethod(types.NewPointer(typ), id); m != nil {
-			// A method found only in MS(*X) must have a
-			// pointer formal receiver; but the actual
-			// value is not a pointer.
-			// Implicit & -- possibly escaping.
-			return m, b.addr(fn, base, true).address(fn)
-		}
-	}
-	return nil, nil
+	last := len(indices) - 1
+	return emitImplicitSelections(fn, v, indices[:last])
 }
 
 // setCallFunc populates the function parts of a CallCommon structure
@@ -809,53 +775,90 @@ func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) {
 	// Is the call of the form x.f()?
 	sel, ok := unparen(e.Fun).(*ast.SelectorExpr)
 
-	// Case 0: e.Fun evaluates normally to a function.
-	if !ok || fn.Pkg.info.IsPackageRef(sel) != nil {
+	// e.Fun is not a selector.
+	// Evaluate it in the usual way.
+	if !ok {
 		c.Func = b.expr(fn, e.Fun)
 		return
 	}
 
-	// Case 1: X.f() or (*X).f(): a statically dipatched call to
-	// the method f in the method-set of X or *X.  X may be
-	// an interface.  Treat like case 0.
-	// TODO(adonovan): opt: inline expr() here, to make the call static
-	// and to avoid generation of a stub for an interface method.
-	if fn.Pkg.info.IsType(sel.X) {
+	selKind := fn.Pkg.info.ClassifySelector(sel)
+
+	// e.Fun refers to a package-level func or var.
+	// Evaluate it in the usual way.
+	if selKind == token.PACKAGE {
 		c.Func = b.expr(fn, e.Fun)
 		return
 	}
 
-	id := types.Id(fn.Pkg.Object, sel.Sel.Name)
+	typ := fn.Pkg.typeOf(sel.X)
+	obj, indices, isIndirect := types.LookupFieldOrMethod(typ, fn.Pkg.Object, sel.Sel.Name)
 
-	// Let X be the type of x.
+	// T.f() or (*T).f(): a statically dispatched call to the
+	// method f in the method-set of T or *T.
+	// T may be an interface.
+	if selKind == token.TYPE {
+		// e.Fun would evaluate to a concrete method,
+		// interface wrapper function, or promotion wrapper.
+		//
+		// For now, we evaluate it in the usual way.
+		c.Func = b.expr(fn, e.Fun)
 
-	// Case 2: x.f(): a statically dispatched call to a method
-	// from the method-set of X or perhaps *X (if x is addressable
-	// but not a pointer).
-	if m, recv := b.findMethod(fn, sel.X, id); m != nil {
-		c.Func = m
-		c.Args = append(c.Args, recv)
+		// TODO(adonovan): opt: inline expr() here, to make
+		// the call static and to avoid generation of
+		// wrappers.  It's somewhat tricky as it may consume
+		// the first actual parameter if the call is "invoke"
+		// mode.
+		//
+		// Examples:
+		//  type T struct{}; func (T) f() {}   // "call" mode
+		//  type T interface { f() }           // "invoke" mode
+		//
+		//  type S struct{ T }
+		//
+		//  var s S
+		//  S.f(s)
+		//  (*S).f(&s)
+		//
+		// Suggested approach:
+		// - consume the first actual parameter expression
+		//   and build it with b.expr().
+		// - apply implicit field selections.
+		// - use same code as selKind == VAR case to populate fields of c.
 		return
 	}
 
-	switch t := fn.Pkg.typeOf(sel.X).Underlying().(type) {
-	case *types.Struct, *types.Pointer:
-		// Case 3: x.f() where x.f is a function value in a
-		// struct field f; not a method call.  f is a 'var'
-		// (of function type) in the Fields of types.Struct X.
-		// Treat like case 0.
-		c.Func = b.expr(fn, e.Fun)
+	// selKind == token.VAR
 
-	case *types.Interface:
-		// Case 4: x.f() where a dynamically dispatched call
-		// to an interface method f.  f is a 'func' object in
-		// the Methods of types.Interface X
-		c.Method, _ = interfaceMethodIndex(t, id)
-		c.Recv = b.expr(fn, sel.X)
-
-	default:
-		panic(fmt.Sprintf("illegal (%s).%s() call; X:%T", t, sel.Sel.Name, sel.X))
+	switch obj := obj.(type) {
+	case *types.Func:
+		wantAddr := isPointer(recvType(obj))
+		escaping := true
+		v := b.receiver(fn, sel.X, wantAddr, escaping, indices, isIndirect)
+		if _, ok := deref(v.Type()).Underlying().(*types.Interface); ok {
+			if isPointer(v.Type()) {
+				// *struct{I} inherits methods from I.
+				v = emitLoad(fn, v)
 			}
+			// Invoke-mode call.
+			c.Recv = v
+			c.Method = obj
+		} else {
+			// "Call"-mode call.
+			c.Func = fn.Prog.concreteMethod(obj)
+			c.Args = append(c.Args, v)
+		}
+		return
+
+	case *types.Var:
+		// Field access: x.f() where x.f is a function value
+		// in a struct field f; not a method call.
+		// Evaluate it in the usual way.
+		c.Func = b.expr(fn, e.Fun)
+		return
+	}
+
+	panic(fmt.Sprintf("illegal (%s).%s() call; X:%T", typ, sel.Sel.Name, sel.X))
 }
 
 // emitCallArgs emits to f code for the actual parameters of call e to
@@ -910,7 +913,7 @@ func (b *builder) emitCallArgs(fn *Function, sig *types.Signature, e *ast.CallEx
 		} else {
 			// Replace a suffix of args with a slice containing it.
 			at := types.NewArray(vt, int64(len(varargs)))
-			// Don't set pos (e.g. to e.Lparen) for implicit Allocs.
+			// Don't set pos for implicit Allocs.
 			a := emitNew(fn, at, token.NoPos)
 			for i, arg := range varargs {
 				iaddr := &IndexAddr{
@@ -2235,7 +2238,7 @@ func (b *builder) buildDecl(pkg *Package, decl ast.Decl) {
 				}
 				nt := pkg.objectOf(id).Type().(*types.Named)
 				for i, n := 0, nt.NumMethods(); i < n; i++ {
-					b.buildFunction(pkg.Prog.concreteMethods[nt.Method(i)])
+					b.buildFunction(pkg.Prog.concreteMethod(nt.Method(i)))
 				}
 			}
 		}
@@ -2331,9 +2334,9 @@ func (p *Package) Build() {
 	emitStore(init, initguard, vTrue)
 
 	// Call the init() function of each package we import.
-	for _, typkg := range p.info.Imports() {
+	for _, obj := range p.info.Imports() {
 		var v Call
-		v.Call.Func = p.Prog.packages[typkg].init
+		v.Call.Func = p.Prog.packages[obj].init
 		v.Call.pos = init.pos
 		v.setType(types.NewTuple())
 		init.emit(&v)

ssa/builder_test.go

@@ -27,7 +27,7 @@ import (
 func main() {
         var t testing.T
 	t.Parallel()    // static call to external declared method
-        t.Fail()        // static call to synthetic promotion wrapper
+        t.Fail()        // static call to promoted external declared method
         testing.Short() // static call to external package-level function
 
         var w io.Writer = new(bytes.Buffer)
@@ -110,7 +110,7 @@ func main() {
 
 	expectedCallee := []string{
 		"(*testing.T).Parallel",
-		"(*testing.T).Fail",
+		"(*testing.common).Fail",
 		"testing.Short",
 		"N/A",
 	}
@@ -123,7 +123,7 @@ func main() {
 				if want := expectedCallee[callNum]; want != "N/A" {
 					got := call.StaticCallee().String()
 					if want != got {
-						t.Errorf("%dth call from main.main: got callee %s, want %s",
+						t.Errorf("call #%d from main.main: got callee %s, want %s",
 							callNum, got, want)
 					}
 				}

ssa/create.go

@@ -41,8 +41,7 @@ func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
 		packages:            make(map[*types.Package]*Package),
 		builtins:            make(map[types.Object]*Builtin),
 		concreteMethods:     make(map[*types.Func]*Function),
-		indirectionWrappers: make(map[*Function]*Function),
-		boundMethodWrappers: make(map[*Function]*Function),
+		boundMethodWrappers: make(map[*types.Func]*Function),
 		ifaceMethodWrappers: make(map[*types.Func]*Function),
 		mode:                mode,
 	}
@@ -118,23 +117,13 @@ func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node) {
 			pkg.values[obj] = fn
 			pkg.Members[name] = fn
 		} else {
-			// TODO(adonovan): interface methods now have
-			// objects, but we probably don't want to call
-			// memberFromObject for them.
-
-			// Method declaration.
-			// TODO(adonovan) Move this test elsewhere.
-			if _, ok := recv.Type().Underlying().(*types.Interface); ok {
-				return // ignore interface methods
-			}
-			_, method := namedTypeMethodIndex(
-				deref(recv.Type()).(*types.Named),
-				types.Id(pkg.Object, name))
-			pkg.Prog.concreteMethods[method] = fn
+			// Concrete method.
+			_ = deref(recv.Type()).(*types.Named) // assertion
+			pkg.Prog.concreteMethods[obj] = fn
 		}
 
 	default: // (incl. *types.Package)
-		panic(fmt.Sprintf("unexpected Object type: %T", obj))
+		panic("unexpected Object type: " + obj.String())
 	}
 }
 
@@ -239,20 +228,13 @@ func (prog *Program) CreatePackage(info *importer.PackageInfo) *Package {
 		scope := p.Object.Scope()
 		for _, name := range scope.Names() {
 			obj := scope.Lookup(name)
-			if obj, ok := obj.(*types.TypeName); ok {
-				// TODO(adonovan): are the set of Func
-				// objects passed to memberFromObject
-				// duplicate-free?  I doubt it.  Check.
-				mset := types.NewMethodSet(obj.Type())
-				for i, n := 0, mset.Len(); i < n; i++ {
-					memberFromObject(p, mset.At(i).Func, nil)
-				}
-				mset = types.NewMethodSet(types.NewPointer(obj.Type()))
-				for i, n := 0, mset.Len(); i < n; i++ {
-					memberFromObject(p, mset.At(i).Func, nil)
-				}
-			}
 			memberFromObject(p, obj, nil)
+			if obj, ok := obj.(*types.TypeName); ok {
+				named := obj.Type().(*types.Named)
+				for i, n := 0, named.NumMethods(); i < n; i++ {
+					memberFromObject(p, named.Method(i), nil)
+				}
+			}
 		}
 	}
 

ssa/emit.go

@@ -273,7 +273,8 @@ func emitTypeAssert(f *Function, x Value, t types.Type, pos token.Pos) Value {
 	if ti, ok := t.Underlying().(*types.Interface); ok {
 		// Even when ti==txi, we still need ChangeInterface
 		// since it performs a nil-check.
-		if isSuperinterface(ti, txi) {
+		// TODO(adonovan): needs more tests.
+		if types.IsAssignableTo(ti, txi) {
 			c := &ChangeInterface{X: x}
 			c.setPos(pos)
 			c.setType(t)
@@ -347,6 +348,10 @@ func emitTailCall(f *Function, call *Call) {
 // implicit field selections specified by indices to base value v, and
 // returns the selected value.
 //
+// If v is the address of a struct, the result will be the address of
+// a field; if it is the value of a struct, the result will be the
+// value of a field.
+//
 func emitImplicitSelections(f *Function, v Value, indices []int) Value {
 	for _, index := range indices {
 		fld := deref(v.Type()).Underlying().(*types.Struct).Field(index)
@@ -373,3 +378,35 @@ func emitImplicitSelections(f *Function, v Value, indices []int) Value {
 	}
 	return v
 }
+
+// emitFieldSelection emits to f code to select the index'th field of v.
+//
+// If wantAddr, the input must be a pointer-to-struct and the result
+// will be the field's address; otherwise the result will be the
+// field's value.
+//
+func emitFieldSelection(f *Function, v Value, index int, wantAddr bool, pos token.Pos) Value {
+	fld := deref(v.Type()).Underlying().(*types.Struct).Field(index)
+	if isPointer(v.Type()) {
+		instr := &FieldAddr{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(pos)
+		instr.setType(types.NewPointer(fld.Type()))
+		v = f.emit(instr)
+		// Load the field's value iff we don't want its address.
+		if !wantAddr {
+			v = emitLoad(f, v)
+		}
+	} else {
+		instr := &Field{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(pos)
+		instr.setType(fld.Type())
+		v = f.emit(instr)
+	}
+	return v
+}

ssa/func.go

@@ -461,7 +461,8 @@ func (f *Function) emit(instr Instruction) Value {
 //
 // If from==f.Pkg, suppress package qualification.
 func (f *Function) fullName(from *Package) string {
-	// TODO(adonovan): expose less fragile case discrimination.
+	// TODO(adonovan): expose less fragile case discrimination
+	// using f.method.
 
 	// Anonymous?
 	if f.Enclosing != nil {

ssa/interp/interp.go

@@ -133,16 +133,16 @@ func (fr *frame) rundefers() {
 	fr.defers = fr.defers[:0]
 }
 
-// findMethodSet returns the method set for type typ, which may be one
+// lookupMethod returns the method set for type typ, which may be one
 // of the interpreter's fake types.
-func findMethodSet(i *interpreter, typ types.Type) ssa.MethodSet {
+func lookupMethod(i *interpreter, typ types.Type, meth *types.Func) *ssa.Function {
 	switch typ {
 	case rtypeType:
-		return i.rtypeMethods
+		return i.rtypeMethods[meth.Id()]
 	case errorType:
-		return i.errorMethods
+		return i.errorMethods[meth.Id()]
 	}
-	return i.prog.MethodSet(typ)
+	return i.prog.LookupMethod(typ.MethodSet().Lookup(meth.Pkg(), meth.Name()))
 }
 
 // visitInstr interprets a single ssa.Instruction within the activation
@@ -391,11 +391,10 @@ func prepareCall(fr *frame, call *ssa.CallCommon) (fn value, args []value) {
 		if recv.t == nil {
 			panic("method invoked on nil interface")
 		}
-		id := call.MethodId()
-		fn = findMethodSet(fr.i, recv.t)[id]
+		fn = lookupMethod(fr.i, recv.t, call.Method)
 		if fn == nil {
 			// Unreachable in well-typed programs.
-			panic(fmt.Sprintf("method set for dynamic type %v does not contain %s", recv.t, id))
+			panic(fmt.Sprintf("method set for dynamic type %v does not contain %s", recv.t, call.Method))
 		}
 		args = append(args, copyVal(recv.v))
 	}

ssa/interp/testdata/boundmeth.go

@@ -89,6 +89,17 @@ func typeCheck() {
 	_ = i.(func()) // type assertion: receiver type disappears
 }
 
+type errString string
+
+func (err errString) Error() string {
+	return string(err)
+}
+
+// Regression test for a builder crash.
+func regress1(x error) func() string {
+	return x.Error
+}
+
 func main() {
 	valueReceiver()
 	pointerReceiver()
@@ -96,4 +107,8 @@ func main() {
 	promotedReceiver()
 	anonStruct()
 	typeCheck()
+
+	if e := regress1(errString("hi"))(); e != "hi" {
+		panic(e)
+	}
 }

ssa/interp/testdata/ifaceprom.go

@@ -26,10 +26,33 @@ func (impl) two() string {
 func main() {
 	var s S
 	s.I = impl{}
+	if one := s.I.one(); one != 1 {
+		panic(one)
+	}
 	if one := s.one(); one != 1 {
 		panic(one)
 	}
+	closOne := s.I.one
+	if one := closOne(); one != 1 {
+		panic(one)
+	}
+	closOne = s.one
+	if one := closOne(); one != 1 {
+		panic(one)
+	}
+
+	if two := s.I.two(); two != "two" {
+		panic(two)
+	}
 	if two := s.two(); two != "two" {
 		panic(two)
 	}
+	closTwo := s.I.two
+	if two := closTwo(); two != "two" {
+		panic(two)
+	}
+	closTwo = s.two
+	if two := closTwo(); two != "two" {
+		panic(two)
+	}
 }

ssa/print.go

@@ -113,8 +113,7 @@ func printCall(v *CallCommon, prefix string, instr Instruction) string {
 	if !v.IsInvoke() {
 		b.WriteString(relName(v.Func, instr))
 	} else {
-		name := v.Recv.Type().Underlying().(*types.Interface).Method(v.Method).Name()
-		fmt.Fprintf(&b, "invoke %s.%s [#%d]", relName(v.Recv, instr), name, v.Method)
+		fmt.Fprintf(&b, "invoke %s.%s", relName(v.Recv, instr), v.Method.Name())
 	}
 	b.WriteString("(")
 	for i, arg := range v.Args {

ssa/promote.go

@@ -4,10 +4,9 @@ package ssa
 // synthesis of wrapper methods.
 //
 // Wrappers include:
-// - promotion wrappers for methods of embedded fields.
+// - indirection/promotion wrappers for methods of embedded fields.
 // - interface method wrappers for closures of I.f.
 // - bound method wrappers, for uncalled obj.Method closures.
-// - indirection wrappers, for calls to T-methods on a *T receiver.
 
 // TODO(adonovan): rename to wrappers.go.
 
@@ -18,35 +17,54 @@ import (
 	"code.google.com/p/go.tools/go/types"
 )
 
+// recvType returns the receiver type of method obj.
+func recvType(obj *types.Func) types.Type {
+	return obj.Type().(*types.Signature).Recv().Type()
+}
+
 // MethodSet returns the method set for type typ, building wrapper
 // methods as needed for embedded field promotion, and indirection for
 // *T receiver types, etc.
 // A nil result indicates an empty set.
 //
+// This function should only be called when you need to construct the
+// entire method set, synthesizing all wrappers, for example during
+// the processing of a MakeInterface instruction or when visiting all
+// reachable functions.
+//
+// If you only need to look up a single method (obj), avoid this
+// function and use LookupMethod instead:
+//
+//      meth := types.MethodSet(typ).Lookup(pkg, name)
+// 	m := prog.MethodSet(typ)[meth.Id()]   // don't do this
+//	m := prog.LookupMethod(meth)          // use this instead
+//
+// If you only need to enumerate the keys, use types.MethodSet
+// instead.
+//
+// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
+//
 // Thread-safe.
 //
 func (prog *Program) MethodSet(typ types.Type) MethodSet {
-	return prog.populateMethodSet(typ, "")
+	return prog.populateMethodSet(typ, nil)
 }
 
 // populateMethodSet returns the method set for typ, ensuring that it
-// contains at least key id.  If id is empty, the entire method set is
-// populated.
+// contains at least the value for obj, if that is a key.
+// If id is empty, the entire method set is populated.
 //
-func (prog *Program) populateMethodSet(typ types.Type, id string) MethodSet {
-	tmset := typ.MethodSet()
+// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
+//
+func (prog *Program) populateMethodSet(typ types.Type, meth *types.Method) MethodSet {
+	tmset := methodSet(typ)
 	n := tmset.Len()
 	if n == 0 {
 		return nil
 	}
-	if _, ok := deref(typ).Underlying().(*types.Interface); ok {
-		// TODO(gri): fix: go/types bug: pointer-to-interface
-		// has no methods---yet go/types says it has!
-		return nil
-	}
 
 	if prog.mode&LogSource != 0 {
-		defer logStack("MethodSet %s id=%s", typ, id)()
+		defer logStack("populateMethodSet %s meth=%v", typ, meth)()
 	}
 
 	prog.methodsMu.Lock()
@@ -59,24 +77,18 @@ func (prog *Program) populateMethodSet(typ types.Type, id string) MethodSet {
 	}
 
 	if len(mset) < n {
-		if id != "" { // single method
-			// tmset.Lookup() is no use to us with only an Id string.
+		if meth != nil { // single method
+			id := meth.Id()
 			if mset[id] == nil {
-				for i := 0; i < n; i++ {
-					obj := tmset.At(i)
-					if obj.Id() == id {
-						mset[id] = makeMethod(prog, typ, obj)
-						return mset
+				mset[id] = findMethod(prog, meth)
 			}
-				}
-			}
-		}
-
+		} else {
 			// complete set
 			for i := 0; i < n; i++ {
-			obj := tmset.At(i)
-			if id := obj.Id(); mset[id] == nil {
-				mset[id] = makeMethod(prog, typ, obj)
+				meth := tmset.At(i)
+				if id := meth.Id(); mset[id] == nil {
+					mset[id] = findMethod(prog, meth)
+				}
 			}
 		}
 	}
@@ -84,49 +96,70 @@ func (prog *Program) populateMethodSet(typ types.Type, id string) MethodSet {
 	return mset
 }
 
+func methodSet(typ types.Type) *types.MethodSet {
+	// TODO(adonovan): temporary workaround.  Inline it away when fixed.
+	if _, ok := deref(typ).Underlying().(*types.Interface); ok && isPointer(typ) {
+		// TODO(gri): fix: go/types bug: pointer-to-interface
+		// has no methods---yet go/types says it has!
+		return new(types.MethodSet)
+	}
+	return typ.MethodSet()
+}
+
 // LookupMethod returns the method id of type typ, building wrapper
 // methods on demand.  It returns nil if the typ has no such method.
 //
 // Thread-safe.
 //
-func (prog *Program) LookupMethod(typ types.Type, id string) *Function {
-	return prog.populateMethodSet(typ, id)[id]
+// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
+//
+func (prog *Program) LookupMethod(meth *types.Method) *Function {
+	return prog.populateMethodSet(meth.Recv(), meth)[meth.Id()]
 }
 
-// makeMethod returns the concrete Function for the method obj,
-// adapted if necessary so that its receiver type is typ.
+// concreteMethod returns the concrete method denoted by obj.
+// Panic ensues if there is no such method (e.g. it's a standalone
+// function).
+//
+func (prog *Program) concreteMethod(obj *types.Func) *Function {
+	fn := prog.concreteMethods[obj]
+	if fn == nil {
+		panic("no concrete method: " + obj.String())
+	}
+	return fn
+}
+
+// findMethod returns the concrete Function for the method meth,
+// synthesizing wrappers as needed.
 //
 // EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
 //
-func makeMethod(prog *Program, typ types.Type, obj *types.Method) *Function {
-	// Promoted method accessed via implicit field selections?
-	if len(obj.Index()) > 1 {
-		return promotionWrapper(prog, typ, obj)
+func findMethod(prog *Program, meth *types.Method) *Function {
+	needsPromotion := len(meth.Index()) > 1
+	needsIndirection := !isPointer(recvType(meth.Func)) && isPointer(meth.Recv())
+
+	if needsPromotion || needsIndirection {
+		return makeWrapper(prog, meth.Recv(), meth)
 	}
 
-	method := prog.concreteMethods[obj.Func]
-	if method == nil {
-		panic("no concrete method for " + obj.Func.String())
+	if _, ok := meth.Recv().Underlying().(*types.Interface); ok {
+		return interfaceMethodWrapper(prog, meth.Recv(), meth.Func)
 	}
 
-	// Call to method on T from receiver of type *T?
-	if !isPointer(method.Signature.Recv().Type()) && isPointer(typ) {
-		method = indirectionWrapper(method)
-	}
-
-	return method
+	// Invariant: fn.Signature.Recv().Type() == recvType(meth.Func)
+	return prog.concreteMethod(meth.Func)
 }
 
-// promotionWrapper returns a synthetic wrapper Function that performs
-// a sequence of implicit field selections then tailcalls a "promoted"
-// method.  For example, given these decls:
+// makeWrapper returns a synthetic wrapper Function that optionally
+// performs receiver indirection, implicit field selections and then a
+// tailcall of a "promoted" method.  For example, given these decls:
 //
 //    type A struct {B}
 //    type B struct {*C}
 //    type C ...
 //    func (*C) f()
 //
-// then promotionWrapper(typ=A, obj={Func:(*C).f, Indices=[B,C,f]})
+// then makeWrapper(typ=A, obj={Func:(*C).f, Indices=[B,C,f]})
 // synthesize this wrapper method:
 //
 //    func (a A) f() { return a.B.C->f() }
@@ -138,23 +171,21 @@ func makeMethod(prog *Program, typ types.Type, obj *types.Method) *Function {
 //
 // EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
 //
-func promotionWrapper(prog *Program, typ types.Type, obj *types.Method) *Function {
-	old := obj.Func.Type().(*types.Signature)
+func makeWrapper(prog *Program, typ types.Type, meth *types.Method) *Function {
+	old := meth.Func.Type().(*types.Signature)
 	sig := types.NewSignature(nil, types.NewVar(token.NoPos, nil, "recv", typ), old.Params(), old.Results(), old.IsVariadic())
 
-	// TODO(adonovan): include implicit field path in description.
-	description := fmt.Sprintf("promotion wrapper for (%s).%s", old.Recv(), obj.Func.Name())
-
+	description := fmt.Sprintf("wrapper for (%s).%s", old.Recv(), meth.Func.Name())
 	if prog.mode&LogSource != 0 {
 		defer logStack("make %s to (%s)", description, typ)()
 	}
 	fn := &Function{
-		name:      obj.Name(),
-		object:    obj,
+		name:      meth.Name(),
+		method:    meth,
 		Signature: sig,
 		Synthetic: description,
 		Prog:      prog,
-		pos:       obj.Pos(),
+		pos:       meth.Pos(),
 	}
 	fn.startBody()
 	fn.addSpilledParam(sig.Recv())
@@ -162,6 +193,8 @@ func promotionWrapper(prog *Program, typ types.Type, obj *types.Method) *Functio
 
 	var v Value = fn.Locals[0] // spilled receiver
 	if isPointer(typ) {
+		// TODO(adonovan): consider emitting a nil-pointer check here
+		// with a nice error message, like gc does.
 		v = emitLoad(fn, v)
 	}
 
@@ -173,7 +206,7 @@ func promotionWrapper(prog *Program, typ types.Type, obj *types.Method) *Functio
 	// Load) in preference to value extraction (Field possibly
 	// preceded by Load).
 
-	indices := obj.Index()
+	indices := meth.Index()
 	v = emitImplicitSelections(fn, v, indices[:len(indices)-1])
 
 	// Invariant: v is a pointer, either
@@ -185,14 +218,10 @@ func promotionWrapper(prog *Program, typ types.Type, obj *types.Method) *Functio
 		if !isPointer(old.Recv().Type()) {
 			v = emitLoad(fn, v)
 		}
-		m := prog.concreteMethods[obj.Func]
-		if m == nil {
-			panic("oops: " + fn.Synthetic)
-		}
-		c.Call.Func = m
+		c.Call.Func = prog.concreteMethod(meth.Func)
 		c.Call.Args = append(c.Call.Args, v)
 	} else {
-		c.Call.Method = indices[len(indices)-1]
+		c.Call.Method = meth.Func
 		c.Call.Recv = emitLoad(fn, v)
 	}
 	for _, arg := range fn.Params[1:] {
@@ -219,9 +248,9 @@ func createParams(fn *Function) {
 
 // Wrappers for standalone interface methods ----------------------------------
 
-// interfaceMethodWrapper returns a synthetic wrapper function permitting a
-// method id of interface typ to be called like a standalone function,
-// e.g.:
+// interfaceMethodWrapper returns a synthetic wrapper function
+// permitting an abstract method obj to be called like a standalone
+// function, e.g.:
 //
 //   type I interface { f(x int) R }
 //   m := I.f  // wrapper
@@ -234,38 +263,41 @@ func createParams(fn *Function) {
 //     return i.f(x, ...)
 //   }
 //
+// typ is the type of the receiver (I here).  It isn't necessarily
+// equal to the recvType(obj) because one interface may embed another.
+// TODO(adonovan): more tests.
+//
 // TODO(adonovan): opt: currently the stub is created even when used
 // in call position: I.f(i, 0).  Clearly this is suboptimal.
 //
-// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
+// EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
 //
-func interfaceMethodWrapper(prog *Program, typ types.Type, id string) *Function {
-	index, meth := interfaceMethodIndex(typ.Underlying().(*types.Interface), id)
-	prog.methodsMu.Lock()
-	defer prog.methodsMu.Unlock()
+func interfaceMethodWrapper(prog *Program, typ types.Type, obj *types.Func) *Function {
 	// If one interface embeds another they'll share the same
 	// wrappers for common methods.  This is safe, but it might
 	// confuse some tools because of the implicit interface
 	// conversion applied to the first argument.  If this becomes
 	// a problem, we should include 'typ' in the memoization key.
-	fn, ok := prog.ifaceMethodWrappers[meth]
+	fn, ok := prog.ifaceMethodWrappers[obj]
 	if !ok {
+		description := fmt.Sprintf("interface method wrapper for %s.%s", typ, obj)
 		if prog.mode&LogSource != 0 {
-			defer logStack("interfaceMethodWrapper %s.%s", typ, id)()
+			defer logStack("%s", description)()
 		}
 		fn = &Function{
-			name:      meth.Name(),
-			object:    meth,
-			Signature: meth.Type().(*types.Signature),
-			Synthetic: fmt.Sprintf("interface method wrapper for %s.%s", typ, id),
-			pos:       meth.Pos(),
+			name:      obj.Name(),
+			object:    obj,
+			Signature: obj.Type().(*types.Signature),
+			Synthetic: description,
+			pos:       obj.Pos(),
 			Prog:      prog,
 		}
 		fn.startBody()
 		fn.addParam("recv", typ, token.NoPos)
 		createParams(fn)
 		var c Call
-		c.Call.Method = index
+
+		c.Call.Method = obj
 		c.Call.Recv = fn.Params[0]
 		for _, arg := range fn.Params[1:] {
 			c.Call.Args = append(c.Call.Args, arg)
@@ -273,7 +305,7 @@ func interfaceMethodWrapper(prog *Program, typ types.Type, id string) *Function
 		emitTailCall(fn, &c)
 		fn.finishBody()
 
-		prog.ifaceMethodWrappers[meth] = fn
+		prog.ifaceMethodWrappers[obj] = fn
 	}
 	return fn
 }
@@ -281,12 +313,12 @@ func interfaceMethodWrapper(prog *Program, typ types.Type, id string) *Function
 // Wrappers for bound methods -------------------------------------------------
 
 // boundMethodWrapper returns a synthetic wrapper function that
-// delegates to a concrete method.  The wrapper has one free variable,
-// the method's receiver.  Use MakeClosure with such a wrapper to
-// construct a bound-method closure.
-// e.g.:
+// delegates to a concrete or interface method.
+// The wrapper has one free variable, the method's receiver.
+// Use MakeClosure with such a wrapper to construct a bound-method
+// closure.  e.g.:
 //
-//   type T int
+//   type T int          or:  type T interface { meth() }
 //   func (t T) meth()
 //   var t T
 //   f := t.meth
@@ -298,22 +330,22 @@ func interfaceMethodWrapper(prog *Program, typ types.Type, id string) *Function
 //
 // EXCLUSIVE_LOCKS_ACQUIRED(meth.Prog.methodsMu)
 //
-func boundMethodWrapper(meth *Function) *Function {
-	prog := meth.Prog
+func boundMethodWrapper(prog *Program, obj *types.Func) *Function {
 	prog.methodsMu.Lock()
 	defer prog.methodsMu.Unlock()
-	fn, ok := prog.boundMethodWrappers[meth]
+	fn, ok := prog.boundMethodWrappers[obj]
 	if !ok {
+		description := fmt.Sprintf("bound method wrapper for %s", obj)
 		if prog.mode&LogSource != 0 {
-			defer logStack("boundMethodWrapper %s", meth)()
+			defer logStack("%s", description)()
 		}
-		s := meth.Signature
+		s := obj.Type().(*types.Signature)
 		fn = &Function{
-			name:      "bound$" + meth.String(),
+			name:      "bound$" + obj.String(),
 			Signature: types.NewSignature(nil, nil, s.Params(), s.Results(), s.IsVariadic()), // drop recv
-			Synthetic: "bound method wrapper for " + meth.String(),
+			Synthetic: description,
 			Prog:      prog,
-			pos:       meth.Pos(),
+			pos:       obj.Pos(),
 		}
 
 		cap := &Capture{name: "recv", typ: s.Recv().Type(), parent: fn}
@@ -321,65 +353,21 @@ func boundMethodWrapper(meth *Function) *Function {
 		fn.startBody()
 		createParams(fn)
 		var c Call
-		c.Call.Func = meth
+
+		if _, ok := recvType(obj).Underlying().(*types.Interface); !ok { // concrete
+			c.Call.Func = prog.concreteMethod(obj)
 			c.Call.Args = []Value{cap}
+		} else {
+			c.Call.Recv = cap
+			c.Call.Method = obj
+		}
 		for _, arg := range fn.Params {
 			c.Call.Args = append(c.Call.Args, arg)
 		}
 		emitTailCall(fn, &c)
 		fn.finishBody()
 
-		prog.boundMethodWrappers[meth] = fn
-	}
-	return fn
-}
-
-// Receiver indirection wrapper ------------------------------------
-
-// indirectionWrapper returns a synthetic method with *T receiver
-// that delegates to meth, which has a T receiver.
-//
-//      func (recv *T) f(...) ... {
-//              return (*recv).f(...)
-//      }
-//
-// EXCLUSIVE_LOCKS_REQUIRED(meth.Prog.methodsMu)
-//
-func indirectionWrapper(meth *Function) *Function {
-	prog := meth.Prog
-	fn, ok := prog.indirectionWrappers[meth]
-	if !ok {
-		if prog.mode&LogSource != 0 {
-			defer logStack("makeIndirectionWrapper %s", meth)()
-		}
-
-		s := meth.Signature
-		recv := types.NewVar(token.NoPos, meth.Pkg.Object, "recv",
-			types.NewPointer(s.Recv().Type()))
-		// TODO(adonovan): is there a *types.Func for this method?
-		fn = &Function{
-			name:      meth.Name(),
-			Signature: types.NewSignature(nil, recv, s.Params(), s.Results(), s.IsVariadic()),
-			Prog:      prog,
-			Synthetic: "receiver indirection wrapper for " + meth.String(),
-			pos:       meth.Pos(),
-		}
-
-		fn.startBody()
-		fn.addParamObj(recv)
-		createParams(fn)
-		// TODO(adonovan): consider emitting a nil-pointer check here
-		// with a nice error message, like gc does.
-		var c Call
-		c.Call.Func = meth
-		c.Call.Args = append(c.Call.Args, emitLoad(fn, fn.Params[0]))
-		for _, arg := range fn.Params[1:] {
-			c.Call.Args = append(c.Call.Args, arg)
-		}
-		emitTailCall(fn, &c)
-		fn.finishBody()
-
-		prog.indirectionWrappers[meth] = fn
+		prog.boundMethodWrappers[obj] = fn
 	}
 	return fn
 }

ssa/source.go

@@ -257,6 +257,8 @@ func (prog *Program) ConstValue(obj *types.Const) *Const {
 // because its package was not built, the DebugInfo flag was not set
 // during SSA construction, or the value was optimized away.
 //
+// TODO(adonovan): test on x.f where x is a field.
+//
 // ref must be the path to an ast.Ident (e.g. from
 // PathEnclosingInterval), and that ident must resolve to obj.
 //

ssa/ssa.go

@@ -22,13 +22,12 @@ type Program struct {
 	PackagesByPath  map[string]*Package         // all loaded Packages, keyed by import path
 	packages        map[*types.Package]*Package // all loaded Packages, keyed by object
 	builtins        map[types.Object]*Builtin   // all built-in functions, keyed by typechecker objects.
-	concreteMethods map[*types.Func]*Function   // maps named concrete methods to their code
+	concreteMethods map[*types.Func]*Function   // maps declared concrete methods to their code
 	mode            BuilderMode                 // set of mode bits for SSA construction
 
 	methodsMu           sync.Mutex                // guards the following maps:
 	methodSets          typemap.M                 // maps type to its concrete MethodSet
-	indirectionWrappers map[*Function]*Function   // func(*T) wrappers for T-methods
-	boundMethodWrappers map[*Function]*Function   // wrappers for curried x.Method closures
+	boundMethodWrappers map[*types.Func]*Function // wrappers for curried x.Method closures
 	ifaceMethodWrappers map[*types.Func]*Function // wrappers for curried I.Method functions
 }
 
@@ -73,6 +72,10 @@ type Member interface {
 // The keys of a method set are strings returned by the types.Id()
 // function.
 //
+// TODO(adonovan): encapsulate the representation behind both Id-based
+// and types.Method-based accessors and enable lazy population.
+// Perhaps hide it entirely within the Program API.
+//
 type MethodSet map[string]*Function
 
 // A Type is a Member of a Package representing a package-level named type.
@@ -250,7 +253,8 @@ type Instruction interface {
 //
 type Function struct {
 	name      string
-	object    types.Object // a *types.Func; may be nil for init, wrappers, etc.
+	object    types.Object  // a declared *types.Func; nil for init, wrappers, etc.
+	method    *types.Method // info about provenance of synthetic methods [currently unused]
 	Signature *types.Signature
 	pos       token.Pos
 
@@ -1177,7 +1181,7 @@ type anInstruction struct {
 // Each CallCommon exists in one of two modes, function call and
 // interface method invocation, or "call" and "invoke" for short.
 //
-// 1. "call" mode: when Recv is nil (!IsInvoke), a CallCommon
+// 1. "call" mode: when Method is nil (!IsInvoke), a CallCommon
 // represents an ordinary function call of the value in Func.
 //
 // In the common case in which Func is a *Function, this indicates a
@@ -1197,10 +1201,10 @@ type anInstruction struct {
 // 	go t3()
 //	defer t5(...t6)
 //
-// 2. "invoke" mode: when Recv is non-nil (IsInvoke), a CallCommon
+// 2. "invoke" mode: when Method is non-nil (IsInvoke), a CallCommon
 // represents a dynamically dispatched call to an interface method.
-// In this mode, Recv is the interface value and Method is the index
-// of the method within the interface type of the receiver.
+// In this mode, Recv is the interface value and Method is the
+// interface's abstract method.
 //
 // Recv is implicitly supplied to the concrete method implementation
 // as the receiver parameter; in other words, Args[0] holds not the
@@ -1219,9 +1223,10 @@ type anInstruction struct {
 // readability of the printed form.)
 //
 type CallCommon struct {
-	Recv        Value     // receiver, iff interface method invocation
-	Method      int       // index of interface method; call MethodId() for its Id
-	Func        Value     // target of call, iff function call
+	// TODO(adonovan): combine Recv/Func fields since Method now discriminates.
+	Recv        Value       // receiver (in "invoke" mode)
+	Method      *types.Func // abstract method (in "invoke" mode)
+	Func        Value       // target of call (in "call" mode)
 	Args        []Value     // actual parameters, including receiver in invoke mode
 	HasEllipsis bool        // true iff last Args is a slice of '...' args (needed?)
 	pos         token.Pos   // position of CallExpr.Lparen, iff explicit in source
@@ -1229,7 +1234,7 @@ type CallCommon struct {
 
 // IsInvoke returns true if this call has "invoke" (not "call") mode.
 func (c *CallCommon) IsInvoke() bool {
-	return c.Recv != nil
+	return c.Method != nil
 }
 
 func (c *CallCommon) Pos() token.Pos { return c.pos }
@@ -1245,9 +1250,8 @@ func (c *CallCommon) Pos() token.Pos { return c.pos }
 // Signature returns nil for a call to a built-in function.
 //
 func (c *CallCommon) Signature() *types.Signature {
-	if c.Recv != nil {
-		iface := c.Recv.Type().Underlying().(*types.Interface)
-		return iface.Method(c.Method).Type().(*types.Signature)
+	if c.Method != nil {
+		return c.Method.Type().(*types.Signature)
 	}
 	sig, _ := c.Func.Type().Underlying().(*types.Signature) // nil for *Builtin
 	return sig
@@ -1265,12 +1269,6 @@ func (c *CallCommon) StaticCallee() *Function {
 	return nil
 }
 
-// MethodId returns the Id for the method called by c, which must
-// have "invoke" mode.
-func (c *CallCommon) MethodId() string {
-	return c.Recv.Type().Underlying().(*types.Interface).Method(c.Method).Id()
-}
-
 // Description returns a description of the mode of this call suitable
 // for a user interface, e.g. "static method call".
 func (c *CallCommon) Description() string {

ssa/util.go

@@ -53,59 +53,6 @@ func deref(typ types.Type) types.Type {
 	return typ
 }
 
-// namedTypeMethodIndex returns the method (and its index) named id
-// within the set of explicitly declared concrete methods of named
-// type typ.  If not found, panic ensues.
-//
-func namedTypeMethodIndex(typ *types.Named, id string) (int, *types.Func) {
-	for i, n := 0, typ.NumMethods(); i < n; i++ {
-		m := typ.Method(i)
-		if m.Id() == id {
-			return i, m
-		}
-	}
-	panic(fmt.Sprint("method not found: ", id, " in named type ", typ))
-}
-
-// interfaceMethodIndex returns the method (and its index) named id
-// within the method-set of interface type typ.  If not found, panic
-// ensues.
-//
-func interfaceMethodIndex(typ *types.Interface, id string) (int, *types.Func) {
-	for i, n := 0, typ.NumMethods(); i < n; i++ {
-		m := typ.Method(i)
-		if m.Id() == id {
-			return i, m
-		}
-	}
-	panic(fmt.Sprint("method not found: ", id, " in interface ", typ))
-}
-
-// isSuperinterface returns true if x is a superinterface of y,
-// i.e.  x's methods are a subset of y's.
-//
-func isSuperinterface(x, y *types.Interface) bool {
-	if y.NumMethods() < x.NumMethods() {
-		return false
-	}
-	// TODO(adonovan): opt: this is quadratic.
-outer:
-	for i, n := 0, x.NumMethods(); i < n; i++ {
-		xm := x.Method(i)
-		for j, m := 0, y.NumMethods(); j < m; j++ {
-			ym := y.Method(j)
-			if xm.Id() == ym.Id() {
-				if !types.IsIdentical(xm.Type(), ym.Type()) {
-					return false // common name but conflicting types
-				}
-				continue outer
-			}
-		}
-		return false // y doesn't have this method
-	}
-	return true
-}
-
 // DefaultType 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.