[dev.typeparams] cmd/compile: refactor SelectorExpr code into helpers

This CL refactors the SelectorExpr-handling code added in CL 285373
into helper functions that can eventually be reused by iimport.

Change-Id: I15b4a96c242f63cb370d7492ed08168550724f47
Reviewed-on: https://go-review.googlesource.com/c/go/+/285953
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/noder/expr.go

@@ -107,7 +107,7 @@ func (g *irgen) expr0(typ types2.Type, expr syntax.Expr) ir.Node {
 			}
 		}
 
-		return g.selectorExpr(pos, typ, expr)
+		return g.selectorExpr(pos, expr)
 	case *syntax.SliceExpr:
 		return Slice(pos, g.expr(expr.X), g.expr(expr.Index[0]), g.expr(expr.Index[1]), g.expr(expr.Index[2]))
 
@@ -131,88 +131,55 @@ func (g *irgen) expr0(typ types2.Type, expr syntax.Expr) ir.Node {
 // selectorExpr resolves the choice of ODOT, ODOTPTR, OCALLPART (eventually
 // ODOTMETH & ODOTINTER), and OMETHEXPR and deals with embedded fields here rather
 // than in typecheck.go.
-func (g *irgen) selectorExpr(pos src.XPos, typ types2.Type, expr *syntax.SelectorExpr) ir.Node {
+func (g *irgen) selectorExpr(pos src.XPos, expr *syntax.SelectorExpr) ir.Node {
-	x := g.expr(expr.X)
 	selinfo := g.info.Selections[expr]
-	nindex := len(selinfo.Index())
 
-	// Iterate through the selections from types2. If nindex > 1, then we will
+	// Everything up to the last selection is an implicit embedded field access,
-	// create extra nodes to deal with embedded fields.
+	// and the last selection is determined by selinfo.Kind().
-	for i := 0; i < nindex; i++ {
+	index := selinfo.Index()
-		var f *types.Field
+	embeds, last := index[:len(index)-1], index[len(index)-1]
-		var n *ir.SelectorExpr
 
-		op := ir.ODOT
+	x := g.expr(expr.X)
-		index := selinfo.Index()[i]
+	for _, ix := range embeds {
-		xt := x.Type()
+		x = Implicit(DotField(pos, x, ix))
-		origxt := xt
-		if xt.IsPtr() && !xt.Elem().IsInterface() {
-			// Get to the base type, but remember that we skipped the ptr
-			xt = xt.Elem()
-			op = ir.ODOTPTR
-		}
-		types.CalcSize(xt)
-		// Everything up to the last selection is an embedded field
-		// access, and the last selection is determined by selinfo.Kind().
-		if i < nindex-1 || selinfo.Kind() == types2.FieldVal {
-			f = xt.Field(index)
-			sym := f.Sym
-			n = ir.NewSelectorExpr(pos, op, x, sym)
-			if i < nindex-1 {
-				n.SetImplicit(true)
-				typed(f.Type, n)
-			}
-		} else if selinfo.Kind() == types2.MethodExpr {
-			var ms *types.Fields
-			if xt.IsInterface() {
-				// TODO(danscales,mdempsky): interface method sets
-				// are not sorted the same between types and
-				// types2. In particular, this will likely fail if
-				// an interface contains unexported methods from
-				// two different packages (due to cross-package
-				// interface embedding).
-				ms = xt.Fields()
-			} else {
-				mt := types.ReceiverBaseType(xt)
-				ms = mt.Methods()
-			}
-			f = ms.Slice()[index]
-			n = ir.NewSelectorExpr(pos, ir.OMETHEXPR, x, f.Sym)
-		} else { // types.MethodVal
-			if xt.IsInterface() {
-				f = xt.Field(index)
-			} else {
-				f = xt.Methods().Slice()[index]
-				rcvr := f.Type.Recv().Type
-				if rcvr.IsPtr() && types.Identical(rcvr.Elem(), origxt) {
-					addr := typecheck.NodAddrAt(pos, x)
-					addr.SetImplicit(true)
-					typed(xt.PtrTo(), addr)
-					x = addr
-				} else if op == ir.ODOTPTR && !rcvr.IsPtr() {
-					star := ir.NewStarExpr(pos, x)
-					star.SetImplicit(true)
-					typed(xt, star)
-					x = star
-				}
-			}
-			// We will change OCALLPART to ODOTMETH or ODOTINTER in
-			// Call() if n is actually called.
-			n = ir.NewSelectorExpr(pos, ir.OCALLPART, x, f.Sym)
-		}
-		n.Selection = f
-		x = n
 	}
 
-	// We don't set type on x for the last index (i == nindex - 1), since that
+	kind := selinfo.Kind()
-	// is the actual selection (ignoring embedded fields) and may be an
+	if kind == types2.FieldVal {
-	// OMETHEXPR or OCALLPART operation. In those cases, the type to set on the
+		return DotField(pos, x, last)
-	// node will be different from the type derived from the field/method
+	}
-	// selection. Instead for the last index, we always set the type (at the
+
-	// end of the function) from g.typ(typ).
+	// TODO(danscales,mdempsky): Interface method sets are not sorted the
-	typed(g.typ(typ), x)
+	// same between types and types2. In particular, using "last" here
-	types.CalcSize(x.Type())
+	// without conversion will likely fail if an interface contains
-	return x
+	// unexported methods from two different packages (due to cross-package
+	// interface embedding).
+
+	method := selinfo.Obj().(*types2.Func)
+
+	// Add implicit addr/deref for method values, if needed.
+	if kind == types2.MethodVal && !x.Type().IsInterface() {
+		recvTyp := method.Type().(*types2.Signature).Recv().Type()
+		_, wantPtr := recvTyp.(*types2.Pointer)
+		havePtr := x.Type().IsPtr()
+
+		if havePtr != wantPtr {
+			if havePtr {
+				x = Implicit(Deref(pos, x))
+			} else {
+				x = Implicit(Addr(pos, x))
+			}
+		}
+		if !g.match(x.Type(), recvTyp, false) {
+			base.FatalfAt(pos, "expected %L to have type %v", x, recvTyp)
+		}
+	}
+
+	n := DotMethod(pos, x, last)
+	if have, want := n.Sym(), g.selector(method); have != want {
+		base.FatalfAt(pos, "bad Sym: have %v, want %v", have, want)
+	}
+	return n
 }
 
 func (g *irgen) exprList(expr syntax.Expr) []ir.Node {

src/cmd/compile/internal/noder/helpers.go

@@ -5,11 +5,13 @@
 package noder
 
 import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
-	"go/constant"
 )
 
 // Helpers for constructing typed IR nodes.
@@ -21,6 +23,17 @@ import (
 // results, rather than leaving the caller responsible for using
 // typecheck.Expr or typecheck.Stmt.
 
+type ImplicitNode interface {
+	ir.Node
+	SetImplicit(x bool)
+}
+
+// Implicit returns n after marking it as Implicit.
+func Implicit(n ImplicitNode) ImplicitNode {
+	n.SetImplicit(true)
+	return n
+}
+
 // typed returns n after setting its type to typ.
 func typed(typ *types.Type, n ir.Node) ir.Node {
 	n.SetType(typ)
@@ -40,6 +53,13 @@ func Nil(pos src.XPos, typ *types.Type) ir.Node {
 
 // Expressions
 
+func Addr(pos src.XPos, x ir.Node) *ir.AddrExpr {
+	// TODO(mdempsky): Avoid typecheck.Expr. Probably just need to set OPTRLIT when appropriate.
+	n := typecheck.Expr(typecheck.NodAddrAt(pos, x)).(*ir.AddrExpr)
+	typed(types.NewPtr(x.Type()), n)
+	return n
+}
+
 func Assert(pos src.XPos, x ir.Node, typ *types.Type) ir.Node {
 	return typed(typ, ir.NewTypeAssertExpr(pos, x, nil))
 }
@@ -109,6 +129,58 @@ func Compare(pos src.XPos, typ *types.Type, op ir.Op, x, y ir.Node) ir.Node {
 	return typed(typ, n)
 }
 
+func Deref(pos src.XPos, x ir.Node) *ir.StarExpr {
+	n := ir.NewStarExpr(pos, x)
+	typed(x.Type().Elem(), n)
+	return n
+}
+
+func DotField(pos src.XPos, x ir.Node, index int) *ir.SelectorExpr {
+	op, typ := ir.ODOT, x.Type()
+	if typ.IsPtr() {
+		op, typ = ir.ODOTPTR, typ.Elem()
+	}
+	if !typ.IsStruct() {
+		base.FatalfAt(pos, "DotField of non-struct: %L", x)
+	}
+
+	// TODO(mdempsky): This is the backend's responsibility.
+	types.CalcSize(typ)
+
+	field := typ.Field(index)
+	return dot(pos, field.Type, op, x, field)
+}
+
+func DotMethod(pos src.XPos, x ir.Node, index int) *ir.SelectorExpr {
+	method := method(x.Type(), index)
+
+	// Method expression.
+	// TODO(mdempsky): Handle with a separate helper?
+	if x.Op() == ir.OTYPE {
+		typ := typecheck.NewMethodType(method.Type, x.Type())
+		return dot(pos, typ, ir.OMETHEXPR, x, method)
+	}
+
+	// Method value.
+	typ := typecheck.NewMethodType(method.Type, nil)
+	return dot(pos, typ, ir.OCALLPART, x, method)
+}
+
+func dot(pos src.XPos, typ *types.Type, op ir.Op, x ir.Node, selection *types.Field) *ir.SelectorExpr {
+	n := ir.NewSelectorExpr(pos, op, x, selection.Sym)
+	n.Selection = selection
+	typed(typ, n)
+	return n
+}
+
+// TODO(mdempsky): Move to package types.
+func method(typ *types.Type, index int) *types.Field {
+	if typ.IsInterface() {
+		return typ.Field(index)
+	}
+	return types.ReceiverBaseType(typ).Methods().Index(index)
+}
+
 func Index(pos src.XPos, x, index ir.Node) ir.Node {
 	// TODO(mdempsky): Avoid typecheck.Expr.
 	return typecheck.Expr(ir.NewIndexExpr(pos, x, index))
@@ -124,18 +196,18 @@ func Slice(pos src.XPos, x, low, high, max ir.Node) ir.Node {
 }
 
 func Unary(pos src.XPos, op ir.Op, x ir.Node) ir.Node {
-	typ := x.Type()
 	switch op {
 	case ir.OADDR:
-		// TODO(mdempsky): Avoid typecheck.Expr. Probably just need to set OPTRLIT as needed.
+		return Addr(pos, x)
-		return typed(types.NewPtr(typ), typecheck.Expr(typecheck.NodAddrAt(pos, x)))
 	case ir.ODEREF:
-		return typed(typ.Elem(), ir.NewStarExpr(pos, x))
+		return Deref(pos, x)
-	case ir.ORECV:
-		return typed(typ.Elem(), ir.NewUnaryExpr(pos, op, x))
-	default:
-		return typed(typ, ir.NewUnaryExpr(pos, op, x))
 	}
+
+	typ := x.Type()
+	if op == ir.ORECV {
+		typ = typ.Elem()
+	}
+	return typed(typ, ir.NewUnaryExpr(pos, op, x))
 }
 
 // Statements