[dev.typeparams] cmd/compile: fix getDictionarySym for methods references, write out sub-dictionaries

For method references (only), selectorExpr() now computes n.Selection,
which is the generic method that is selected. This allows us to compute
as needed the proper sub-dictionary for method reference. Also cleans up
some code for distinguishing method references from references to a
field that has a function value (especially in the presence of embedded
fields).

Change-Id: I9c5b789c15537ff48c70ca7a6444aa0420178a3a
Reviewed-on: https://go-review.googlesource.com/c/go/+/332095
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

3 files changed, 48 insertions, 28 deletions

diff --git a/src/cmd/compile/internal/noder/expr.go b/src/cmd/compile/internal/noder/expr.go
index 017e98986f..d974b291d0 100644
--- a/src/cmd/compile/internal/noder/expr.go
+++ b/src/cmd/compile/internal/noder/expr.go
@@ -206,6 +206,30 @@ func (g *irgen) selectorExpr(pos src.XPos, typ types2.Type, expr *syntax.Selecto
 		// only be fully transformed once it has an instantiated type.
 		n := ir.NewSelectorExpr(pos, ir.OXDOT, x, typecheck.Lookup(expr.Sel.Value))
 		typed(g.typ(typ), n)
+
+		// Fill in n.Selection for a generic method reference, even though we
+		// won't use it directly, since it is useful for analysis.
+		// Specifically do not fill in for fields or interfaces methods, so
+		// n.Selection being non-nil means a method reference, rather than an
+		// interface reference or reference to a field with a function value.
+		obj2 := g.info.Selections[expr].Obj()
+		sig := types2.AsSignature(obj2.Type())
+		if sig == nil || sig.Recv() == nil {
+			return n
+		}
+		// recvType is the type of the last embedded field. Because of the
+		// way methods are imported, g.obj(obj2) doesn't work across
+		// packages, so we have to lookup the method via the receiver type.
+		recvType := deref2(sig.Recv().Type())
+		if types2.AsInterface(recvType.Underlying()) != nil {
+			return n
+		}
+
+		index := g.info.Selections[expr].Index()
+		last := index[len(index)-1]
+		recvObj := types2.AsNamed(recvType).Obj()
+		recv := g.pkg(recvObj.Pkg()).Lookup(recvObj.Name()).Def
+		n.Selection = recv.Type().Methods().Index(last)
 		return n
 	}
 
@@ -308,10 +332,7 @@ func (g *irgen) selectorExpr(pos src.XPos, typ types2.Type, expr *syntax.Selecto
 
 // getTargs gets the targs associated with the receiver of a selected method
 func getTargs(selinfo *types2.Selection) []types2.Type {
-	r := selinfo.Recv()
-	if p := types2.AsPointer(r); p != nil {
-		r = p.Elem()
-	}
+	r := deref2(selinfo.Recv())
 	n := types2.AsNamed(r)
 	if n == nil {
 		base.Fatalf("Incorrect type for selinfo %v", selinfo)
diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index b228e40258..c04300a165 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -1282,14 +1282,15 @@ func (g *irgen) getDictionarySym(gf *ir.Name, targs []*types.Type, isMeth bool)
 			if n.Op() == ir.OCALL {
 				call := n.(*ir.CallExpr)
 				if call.X.Op() == ir.OXDOT {
-					subtargs := deref(n.(*ir.CallExpr).X.(*ir.SelectorExpr).X.Type()).RParams()
+					subtargs := deref(call.X.(*ir.SelectorExpr).X.Type()).RParams()
 					s2targs := make([]*types.Type, len(subtargs))
 					for i, t := range subtargs {
 						s2targs[i] = subst.Typ(t)
 					}
-					sym = typecheck.MakeDictName(ir.MethodSym(call.X.(*ir.SelectorExpr).X.Type(), call.X.(*ir.SelectorExpr).Sel), s2targs, true)
+					nameNode := call.X.(*ir.SelectorExpr).Selection.Nname.(*ir.Name)
+					sym = g.getDictionarySym(nameNode, s2targs, true)
 				} else {
-					inst := n.(*ir.CallExpr).X.(*ir.InstExpr)
+					inst := call.X.(*ir.InstExpr)
 					var nameNode *ir.Name
 					var meth *ir.SelectorExpr
 					var isMeth bool
@@ -1325,14 +1326,12 @@ func (g *irgen) getDictionarySym(gf *ir.Name, targs []*types.Type, isMeth bool)
 				for i, t := range subtargs {
 					s2targs[i] = subst.Typ(t)
 				}
-				sym = typecheck.MakeDictName(ir.MethodSym(selExpr.X.Type(), selExpr.Sel), s2targs, true)
+				nameNode := selExpr.Selection.Nname.(*ir.Name)
+				sym = g.getDictionarySym(nameNode, s2targs, true)
 			}
 			// TODO: handle closure cases that need sub-dictionaries, get rid of conditional
 			if sym != nil {
-				// TODO: uncomment once we're sure all the
-				// subdictionaries are created correctly.
-				// Methods above aren't yet generating dictionaries recursively yet.
-				//off = objw.SymPtr(lsym, off, sym.Linksym(), 0)
+				off = objw.SymPtr(lsym, off, sym.Linksym(), 0)
 				infoPrint(" - Subdict %v\n", sym.Name)
 			}
 		}
@@ -1403,18 +1402,14 @@ func (g *irgen) getGfInfo(gn *ir.Name) *gfInfo {
 				infoPrint("  Closure&subdictionary required at generic function value %v\n", n.(*ir.InstExpr).X)
 				info.subDictCalls = append(info.subDictCalls, n)
 			} else if n.Op() == ir.OXDOT && !n.(*ir.SelectorExpr).Implicit() &&
-				!n.(*ir.SelectorExpr).X.Type().IsInterface() &&
+				n.(*ir.SelectorExpr).Selection != nil &&
 				len(n.(*ir.SelectorExpr).X.Type().RParams()) > 0 {
-				// Fix this - doesn't account for embedded fields, etc.
-				field := typecheck.Lookdot1(n.(*ir.SelectorExpr), n.(*ir.SelectorExpr).Sel, n.(*ir.SelectorExpr).X.Type(), n.(*ir.SelectorExpr).X.Type().Fields(), 0)
-				if field == nil {
-					if n.(*ir.SelectorExpr).X.Op() == ir.OTYPE {
-						infoPrint("  Closure&subdictionary required at generic meth expr %v\n", n)
-					} else {
-						infoPrint("  Closure&subdictionary required at generic meth value %v\n", n)
-					}
-					info.subDictCalls = append(info.subDictCalls, n)
+				if n.(*ir.SelectorExpr).X.Op() == ir.OTYPE {
+					infoPrint("  Closure&subdictionary required at generic meth expr %v\n", n)
+				} else {
+					infoPrint("  Closure&subdictionary required at generic meth value %v\n", n)
 				}
+				info.subDictCalls = append(info.subDictCalls, n)
 			}
 			if n.Op() == ir.OCALL && n.(*ir.CallExpr).X.Op() == ir.OFUNCINST {
 				infoPrint("  Subdictionary at generic function call: %v - %v\n", n.(*ir.CallExpr).X.(*ir.InstExpr).X, n)
@@ -1422,7 +1417,7 @@ func (g *irgen) getGfInfo(gn *ir.Name) *gfInfo {
 				info.subDictCalls = append(info.subDictCalls, n)
 			}
 			if n.Op() == ir.OCALL && n.(*ir.CallExpr).X.Op() == ir.OXDOT &&
-				!n.(*ir.CallExpr).X.(*ir.SelectorExpr).X.Type().IsInterface() &&
+				n.(*ir.CallExpr).X.(*ir.SelectorExpr).Selection != nil &&
 				len(deref(n.(*ir.CallExpr).X.(*ir.SelectorExpr).X.Type()).RParams()) > 0 {
 				infoPrint("  Subdictionary at generic method call: %v\n", n)
 				n.(*ir.CallExpr).X.(*ir.SelectorExpr).SetImplicit(true)
diff --git a/src/cmd/compile/internal/noder/types.go b/src/cmd/compile/internal/noder/types.go
index b37793b2d0..a0b7fea7cb 100644
--- a/src/cmd/compile/internal/noder/types.go
+++ b/src/cmd/compile/internal/noder/types.go
@@ -278,11 +278,7 @@ func (g *irgen) fillinMethods(typ *types2.Named, ntyp *types.Type) {
 		methods := make([]*types.Field, typ.NumMethods())
 		for i := range methods {
 			m := typ.Method(i)
-			recvType := types2.AsSignature(m.Type()).Recv().Type()
-			ptr := types2.AsPointer(recvType)
-			if ptr != nil {
-				recvType = ptr.Elem()
-			}
+			recvType := deref2(types2.AsSignature(m.Type()).Recv().Type())
 			var meth *ir.Name
 			if m.Pkg() != g.self {
 				// Imported methods cannot be loaded by name (what
@@ -471,3 +467,11 @@ var dirs = [...]types.ChanDir{
 	types2.SendOnly: types.Csend,
 	types2.RecvOnly: types.Crecv,
 }
+
+// deref2 does a single deref of types2 type t, if it is a pointer type.
+func deref2(t types2.Type) types2.Type {
+	if ptr := types2.AsPointer(t); ptr != nil {
+		t = ptr.Elem()
+	}
+	return t
+}