[dev.typeparams] cmd/compile: add types2-based noder

This CL adds "irgen", a new noding implementation that utilizes types2
to guide IR construction. Notably, it completely skips dealing with
constant and type expressions (aside from using ir.TypeNode to
interoperate with the types1 typechecker), because types2 already
handled those. It also omits any syntax checking, trusting that types2
already rejected any errors.

It currently still utilizes the types1 typechecker for the desugaring
operations it handles (e.g., turning OAS2 into OAS2FUNC/etc, inserting
implicit conversions, rewriting f(g()) functions, and so on). However,
the IR is constructed in a fully incremental fashion, so it should be
easy to now piecemeal replace those dependencies as needed.

Nearly all of "go test std cmd" passes with -G=3 enabled by
default. The main remaining blocker is the number of test/run.go
failures. There also appear to be cases where types2 does not provide
us with position information. These will be iterated upon.

Portions and ideas from Dan Scales's CL 276653.

Change-Id: Ic99e8f2d0267b0312d30c10d5d043f5817a59c9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/281932
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>

1 files changed, 208 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/noder/types.go b/src/cmd/compile/internal/noder/types.go
new file mode 100644
index 00000000000..0635d76077f
--- /dev/null
+++ b/src/cmd/compile/internal/noder/types.go
@@ -0,0 +1,208 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+	"cmd/internal/src"
+)
+
+func (g *irgen) pkg(pkg *types2.Package) *types.Pkg {
+	switch pkg {
+	case nil:
+		return types.BuiltinPkg
+	case g.self:
+		return types.LocalPkg
+	case types2.Unsafe:
+		return ir.Pkgs.Unsafe
+	}
+	return types.NewPkg(pkg.Path(), pkg.Name())
+}
+
+func (g *irgen) typ(typ types2.Type) *types.Type {
+	switch typ := typ.(type) {
+	case *types2.Basic:
+		return g.basic(typ)
+	case *types2.Named:
+		obj := g.obj(typ.Obj())
+		if obj.Op() != ir.OTYPE {
+			base.FatalfAt(obj.Pos(), "expected type: %L", obj)
+		}
+		return obj.Type()
+
+	case *types2.Array:
+		return types.NewArray(g.typ(typ.Elem()), typ.Len())
+	case *types2.Chan:
+		return types.NewChan(g.typ(typ.Elem()), dirs[typ.Dir()])
+	case *types2.Map:
+		return types.NewMap(g.typ(typ.Key()), g.typ(typ.Elem()))
+	case *types2.Pointer:
+		return types.NewPtr(g.typ(typ.Elem()))
+	case *types2.Signature:
+		return g.signature(nil, typ)
+	case *types2.Slice:
+		return types.NewSlice(g.typ(typ.Elem()))
+
+	case *types2.Struct:
+		fields := make([]*types.Field, typ.NumFields())
+		for i := range fields {
+			v := typ.Field(i)
+			f := types.NewField(g.pos(v), g.selector(v), g.typ(v.Type()))
+			f.Note = typ.Tag(i)
+			if v.Embedded() {
+				f.Embedded = 1
+			}
+			fields[i] = f
+		}
+		return types.NewStruct(g.tpkg(typ), fields)
+
+	case *types2.Interface:
+		embeddeds := make([]*types.Field, typ.NumEmbeddeds())
+		for i := range embeddeds {
+			// TODO(mdempsky): Get embedding position.
+			e := typ.EmbeddedType(i)
+			embeddeds[i] = types.NewField(src.NoXPos, nil, g.typ(e))
+		}
+
+		methods := make([]*types.Field, typ.NumExplicitMethods())
+		for i := range methods {
+			m := typ.ExplicitMethod(i)
+			mtyp := g.signature(typecheck.FakeRecv(), m.Type().(*types2.Signature))
+			methods[i] = types.NewField(g.pos(m), g.selector(m), mtyp)
+		}
+
+		return types.NewInterface(g.tpkg(typ), append(embeddeds, methods...))
+
+	default:
+		base.FatalfAt(src.NoXPos, "unhandled type: %v (%T)", typ, typ)
+		panic("unreachable")
+	}
+}
+
+func (g *irgen) signature(recv *types.Field, sig *types2.Signature) *types.Type {
+	do := func(typ *types2.Tuple) []*types.Field {
+		fields := make([]*types.Field, typ.Len())
+		for i := range fields {
+			fields[i] = g.param(typ.At(i))
+		}
+		return fields
+	}
+
+	params := do(sig.Params())
+	results := do(sig.Results())
+	if sig.Variadic() {
+		params[len(params)-1].SetIsDDD(true)
+	}
+
+	return types.NewSignature(g.tpkg(sig), recv, params, results)
+}
+
+func (g *irgen) param(v *types2.Var) *types.Field {
+	return types.NewField(g.pos(v), g.sym(v), g.typ(v.Type()))
+}
+
+func (g *irgen) sym(obj types2.Object) *types.Sym {
+	if name := obj.Name(); name != "" {
+		return g.pkg(obj.Pkg()).Lookup(obj.Name())
+	}
+	return nil
+}
+
+func (g *irgen) selector(obj types2.Object) *types.Sym {
+	pkg, name := g.pkg(obj.Pkg()), obj.Name()
+	if types.IsExported(name) {
+		pkg = types.LocalPkg
+	}
+	return pkg.Lookup(name)
+}
+
+// tpkg returns the package that a function, interface, or struct type
+// expression appeared in.
+//
+// Caveat: For the degenerate types "func()", "interface{}", and
+// "struct{}", tpkg always returns LocalPkg. However, we only need the
+// package information so that go/types can report it via its API, and
+// the reason we fail to return the original package for these
+// particular types is because go/types does *not* report it for
+// them. So in practice this limitation is probably moot.
+func (g *irgen) tpkg(typ types2.Type) *types.Pkg {
+	anyObj := func() types2.Object {
+		switch typ := typ.(type) {
+		case *types2.Signature:
+			if recv := typ.Recv(); recv != nil {
+				return recv
+			}
+			if params := typ.Params(); params.Len() > 0 {
+				return params.At(0)
+			}
+			if results := typ.Results(); results.Len() > 0 {
+				return results.At(0)
+			}
+		case *types2.Struct:
+			if typ.NumFields() > 0 {
+				return typ.Field(0)
+			}
+		case *types2.Interface:
+			if typ.NumExplicitMethods() > 0 {
+				return typ.ExplicitMethod(0)
+			}
+		}
+		return nil
+	}
+
+	if obj := anyObj(); obj != nil {
+		return g.pkg(obj.Pkg())
+	}
+	return types.LocalPkg
+}
+
+func (g *irgen) basic(typ *types2.Basic) *types.Type {
+	switch typ.Name() {
+	case "byte":
+		return types.ByteType
+	case "rune":
+		return types.RuneType
+	}
+	return *basics[typ.Kind()]
+}
+
+var basics = [...]**types.Type{
+	types2.Invalid:        new(*types.Type),
+	types2.Bool:           &types.Types[types.TBOOL],
+	types2.Int:            &types.Types[types.TINT],
+	types2.Int8:           &types.Types[types.TINT8],
+	types2.Int16:          &types.Types[types.TINT16],
+	types2.Int32:          &types.Types[types.TINT32],
+	types2.Int64:          &types.Types[types.TINT64],
+	types2.Uint:           &types.Types[types.TUINT],
+	types2.Uint8:          &types.Types[types.TUINT8],
+	types2.Uint16:         &types.Types[types.TUINT16],
+	types2.Uint32:         &types.Types[types.TUINT32],
+	types2.Uint64:         &types.Types[types.TUINT64],
+	types2.Uintptr:        &types.Types[types.TUINTPTR],
+	types2.Float32:        &types.Types[types.TFLOAT32],
+	types2.Float64:        &types.Types[types.TFLOAT64],
+	types2.Complex64:      &types.Types[types.TCOMPLEX64],
+	types2.Complex128:     &types.Types[types.TCOMPLEX128],
+	types2.String:         &types.Types[types.TSTRING],
+	types2.UnsafePointer:  &types.Types[types.TUNSAFEPTR],
+	types2.UntypedBool:    &types.UntypedBool,
+	types2.UntypedInt:     &types.UntypedInt,
+	types2.UntypedRune:    &types.UntypedRune,
+	types2.UntypedFloat:   &types.UntypedFloat,
+	types2.UntypedComplex: &types.UntypedComplex,
+	types2.UntypedString:  &types.UntypedString,
+	types2.UntypedNil:     &types.Types[types.TNIL],
+}
+
+var dirs = [...]types.ChanDir{
+	types2.SendRecv: types.Cboth,
+	types2.SendOnly: types.Csend,
+	types2.RecvOnly: types.Crecv,
+}