[dev.typeparams] cmd/compile: point StructKeyExpr at the types.Field

When constructing struct literals, importers need a way to specify
precisely which field to initialize without worrying about visibility
or those fields being blank. (A blank field doesn't actually need to
be initialized, but the expression needs to be evaluated still, and
with the right order-of-operations.)

This CL changes StructKeyExpr's Field field to point directly to the
corresponding types.Field, rather than merely holding a copy of its
Sym and Offset. This is akin to past changes to add
SelectorExpr.Selection.

Change-Id: I95b72b1788f73206fcebc22b456cf6b1186db6a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/325031
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 74 insertions, 66 deletions

diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 30d864320f..d52f011072 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -327,9 +327,7 @@ func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
 				}
 				// No pushtype allowed here. Must name fields for that.
 				n1 = AssignConv(n1, f.Type, "field value")
-				sk := ir.NewStructKeyExpr(base.Pos, f.Sym, n1)
-				sk.Offset = f.Offset
-				ls[i] = sk
+				ls[i] = ir.NewStructKeyExpr(base.Pos, f, n1)
 			}
 			if len(ls) < t.NumFields() {
 				base.Errorf("too few values in %v", n)
@@ -339,77 +337,33 @@ func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
 
 			// keyed list
 			ls := n.List
-			for i, l := range ls {
-				ir.SetPos(l)
-
-				if l.Op() == ir.OKEY {
-					kv := l.(*ir.KeyExpr)
-					key := kv.Key
-
-					// Sym might have resolved to name in other top-level
-					// package, because of import dot. Redirect to correct sym
-					// before we do the lookup.
-					s := key.Sym()
-					if id, ok := key.(*ir.Ident); ok && DotImportRefs[id] != nil {
-						s = Lookup(s.Name)
-					}
-
-					// An OXDOT uses the Sym field to hold
-					// the field to the right of the dot,
-					// so s will be non-nil, but an OXDOT
-					// is never a valid struct literal key.
-					if s == nil || s.Pkg != types.LocalPkg || key.Op() == ir.OXDOT || s.IsBlank() {
-						base.Errorf("invalid field name %v in struct initializer", key)
-						continue
-					}
-
-					l = ir.NewStructKeyExpr(l.Pos(), s, kv.Value)
-					ls[i] = l
-				}
-
-				if l.Op() != ir.OSTRUCTKEY {
-					if !errored {
-						base.Errorf("mixture of field:value and value initializers")
-						errored = true
-					}
-					ls[i] = Expr(ls[i])
-					continue
-				}
-				l := l.(*ir.StructKeyExpr)
-
-				f := Lookdot1(nil, l.Field, t, t.Fields(), 0)
-				if f == nil {
-					if ci := Lookdot1(nil, l.Field, t, t.Fields(), 2); ci != nil { // Case-insensitive lookup.
-						if visible(ci.Sym) {
-							base.Errorf("unknown field '%v' in struct literal of type %v (but does have %v)", l.Field, t, ci.Sym)
-						} else if nonexported(l.Field) && l.Field.Name == ci.Sym.Name { // Ensure exactness before the suggestion.
-							base.Errorf("cannot refer to unexported field '%v' in struct literal of type %v", l.Field, t)
-						} else {
-							base.Errorf("unknown field '%v' in struct literal of type %v", l.Field, t)
+			for i, n := range ls {
+				ir.SetPos(n)
+
+				sk, ok := n.(*ir.StructKeyExpr)
+				if !ok {
+					kv, ok := n.(*ir.KeyExpr)
+					if !ok {
+						if !errored {
+							base.Errorf("mixture of field:value and value initializers")
+							errored = true
 						}
+						ls[i] = Expr(n)
 						continue
 					}
-					var f *types.Field
-					p, _ := dotpath(l.Field, t, &f, true)
-					if p == nil || f.IsMethod() {
-						base.Errorf("unknown field '%v' in struct literal of type %v", l.Field, t)
+
+					sk = tcStructLitKey(t, kv)
+					if sk == nil {
 						continue
 					}
-					// dotpath returns the parent embedded types in reverse order.
-					var ep []string
-					for ei := len(p) - 1; ei >= 0; ei-- {
-						ep = append(ep, p[ei].field.Sym.Name)
-					}
-					ep = append(ep, l.Field.Name)
-					base.Errorf("cannot use promoted field %v in struct literal of type %v", strings.Join(ep, "."), t)
-					continue
+
+					fielddup(sk.Sym().Name, hash)
 				}
-				fielddup(f.Sym.Name, hash)
-				l.Offset = f.Offset
 
 				// No pushtype allowed here. Tried and rejected.
-				l.Value = Expr(l.Value)
-				l.Value = AssignConv(l.Value, f.Type, "field value")
+				sk.Value = Expr(sk.Value)
+				sk.Value = AssignConv(sk.Value, sk.Field.Type, "field value")
+				ls[i] = sk
 			}
 		}
 
@@ -420,6 +374,60 @@ func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
 	return n
 }
 
+// tcStructLitKey typechecks an OKEY node that appeared within a
+// struct literal.
+func tcStructLitKey(typ *types.Type, kv *ir.KeyExpr) *ir.StructKeyExpr {
+	key := kv.Key
+
+	// Sym might have resolved to name in other top-level
+	// package, because of import dot. Redirect to correct sym
+	// before we do the lookup.
+	sym := key.Sym()
+	if id, ok := key.(*ir.Ident); ok && DotImportRefs[id] != nil {
+		sym = Lookup(sym.Name)
+	}
+
+	// An OXDOT uses the Sym field to hold
+	// the field to the right of the dot,
+	// so s will be non-nil, but an OXDOT
+	// is never a valid struct literal key.
+	if sym == nil || sym.Pkg != types.LocalPkg || key.Op() == ir.OXDOT || sym.IsBlank() {
+		base.Errorf("invalid field name %v in struct initializer", key)
+		return nil
+	}
+
+	if f := Lookdot1(nil, sym, typ, typ.Fields(), 0); f != nil {
+		return ir.NewStructKeyExpr(kv.Pos(), f, kv.Value)
+	}
+
+	if ci := Lookdot1(nil, sym, typ, typ.Fields(), 2); ci != nil { // Case-insensitive lookup.
+		if visible(ci.Sym) {
+			base.Errorf("unknown field '%v' in struct literal of type %v (but does have %v)", sym, typ, ci.Sym)
+		} else if nonexported(sym) && sym.Name == ci.Sym.Name { // Ensure exactness before the suggestion.
+			base.Errorf("cannot refer to unexported field '%v' in struct literal of type %v", sym, typ)
+		} else {
+			base.Errorf("unknown field '%v' in struct literal of type %v", sym, typ)
+		}
+		return nil
+	}
+
+	var f *types.Field
+	p, _ := dotpath(sym, typ, &f, true)
+	if p == nil || f.IsMethod() {
+		base.Errorf("unknown field '%v' in struct literal of type %v", sym, typ)
+		return nil
+	}
+
+	// dotpath returns the parent embedded types in reverse order.
+	var ep []string
+	for ei := len(p) - 1; ei >= 0; ei-- {
+		ep = append(ep, p[ei].field.Sym.Name)
+	}
+	ep = append(ep, sym.Name)
+	base.Errorf("cannot use promoted field %v in struct literal of type %v", strings.Join(ep, "."), typ)
+	return nil
+}
+
 // tcConv typechecks an OCONV node.
 func tcConv(n *ir.ConvExpr) ir.Node {
 	types.CheckSize(n.Type()) // ensure width is calculated for backend