1 files changed, 48 insertions, 21 deletions

diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go
index 83979a91c8..5481812b18 100644
--- a/src/cmd/compile/internal/noder/reader.go
+++ b/src/cmd/compile/internal/noder/reader.go
@@ -2125,16 +2125,32 @@ func usedLocals(body []ir.Node) ir.NameSet {
 // method wrappers.
 var needWrapperTypes []*types.Type
 
-func (r *reader) needWrapper(typ *types.Type) *types.Type {
-	// TODO(mdempsky): Be more judicious about generating wrappers.
-	// For now, generating all possible wrappers is simple and correct,
-	// but potentially wastes a lot of time/space.
+// haveWrapperTypes lists types for which we know we already have
+// method wrappers, because we found the type in an imported package.
+var haveWrapperTypes []*types.Type
 
+func (r *reader) needWrapper(typ *types.Type) *types.Type {
 	if typ.IsPtr() {
 		base.Fatalf("bad pointer type: %v", typ)
 	}
 
-	needWrapperTypes = append(needWrapperTypes, typ)
+	// If a type was found in an imported package, then we can assume
+	// that package (or one of its transitive dependencies) already
+	// generated method wrappers for it.
+	//
+	// Exception: If we're instantiating an imported generic type or
+	// function, we might be instantiating it with type arguments not
+	// previously seen before.
+	//
+	// TODO(mdempsky): Distinguish when a generic function or type was
+	// instantiated in an imported package so that we can add types to
+	// haveWrapperTypes instead.
+	if r.p != localPkgReader && !r.hasTypeParams() {
+		haveWrapperTypes = append(haveWrapperTypes, typ)
+	} else {
+		needWrapperTypes = append(needWrapperTypes, typ)
+	}
+
 	return typ
 }
 
@@ -2143,21 +2159,33 @@ func (r *reader) wrapTypes(target *ir.Package) {
 	r.needWrapper(types.ErrorType)
 
 	seen := make(map[string]*types.Type)
-	for _, typ := range needWrapperTypes {
-		if typ.Sym() == nil {
-			key := typ.LinkString()
-			if prev := seen[key]; prev != nil {
-				if !types.Identical(typ, prev) {
-					base.Fatalf("collision: types %v and %v have short string %q", typ, prev, key)
-				}
-				continue
+	addType := func(typ *types.Type) bool {
+		if typ.Sym() != nil {
+			return true
+		}
+
+		key := typ.LinkString()
+		if prev := seen[key]; prev != nil {
+			if !types.Identical(typ, prev) {
+				base.Fatalf("collision: types %v and %v have short string %q", typ, prev, key)
 			}
-			seen[key] = typ
+			return false
 		}
 
-		r.wrapType(typ, target)
+		seen[key] = typ
+		return true
 	}
 
+	for _, typ := range haveWrapperTypes {
+		addType(typ)
+	}
+	haveWrapperTypes = nil
+
+	for _, typ := range needWrapperTypes {
+		if addType(typ) {
+			r.wrapType(typ, target)
+		}
+	}
 	needWrapperTypes = nil
 }
 
@@ -2243,12 +2271,6 @@ func (r *reader) methodValueWrapper(tbase *types.Type, method *types.Field, targ
 	assert(!sym.Uniq())
 	sym.SetUniq(true)
 
-	// TODO(mdempsky): Fix typecheck to not depend on creation of
-	// imported method value wrappers.
-	if false && !reflectdata.NeedEmit(tbase) {
-		return
-	}
-
 	// TODO(mdempsky): Use method.Pos instead?
 	pos := base.AutogeneratedPos
 
@@ -2258,6 +2280,11 @@ func (r *reader) methodValueWrapper(tbase *types.Type, method *types.Field, targ
 	// Declare and initialize variable holding receiver.
 	recv := ir.NewHiddenParam(pos, fn, typecheck.Lookup(".this"), recvType)
 
+	if !reflectdata.NeedEmit(tbase) {
+		typecheck.Func(fn)
+		return
+	}
+
 	addTailCall(pos, fn, recv, method)
 
 	r.finishWrapperFunc(fn, target)