[dev.typeparams] cmd/compile: start translating type params in noder2

Also, make some fmt changes so that the type parameters and the
typeparam type are displayed in -W=2.

You can now parse a simple generic function (but not generic calls or generic
types) and print out the noder IR via 'go tool compile -G=2 -W=2 func.go'

Change-Id: I1f070fc4a96174a447763ad37999e61c25905901
Reviewed-on: https://go-review.googlesource.com/c/go/+/287833
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

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

@@ -100,6 +100,12 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 
 		return types.NewInterface(g.tpkg(typ), append(embeddeds, methods...))
 
+	case *types2.TypeParam:
+		tp := types.NewTypeParam(g.tpkg(typ), g.typ(typ.Bound()))
+		// Save the name of the type parameter in the sym of the type.
+		tp.SetSym(g.sym(typ.Obj()))
+		return tp
+
 	default:
 		base.FatalfAt(src.NoXPos, "unhandled type: %v (%T)", typ, typ)
 		panic("unreachable")
@@ -107,6 +113,13 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 }
 
 func (g *irgen) signature(recv *types.Field, sig *types2.Signature) *types.Type {
+	tparams2 := sig.TParams()
+	tparams := make([]*types.Field, len(tparams2))
+	for i := range tparams {
+		tp := tparams2[i]
+		tparams[i] = types.NewField(g.pos(tp), g.sym(tp), g.typ(tp.Type()))
+	}
+
 	do := func(typ *types2.Tuple) []*types.Field {
 		fields := make([]*types.Field, typ.Len())
 		for i := range fields {
@@ -114,14 +127,13 @@ func (g *irgen) signature(recv *types.Field, sig *types2.Signature) *types.Type
 		}
 		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, nil, params, results)
+	return types.NewSignature(g.tpkg(sig), recv, tparams, params, results)
 }
 
 func (g *irgen) param(v *types2.Var) *types.Field {

src/cmd/compile/internal/types/fmt.go

@@ -318,7 +318,7 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 	}
 
 	// Unless the 'L' flag was specified, if the type has a name, just print that name.
-	if verb != 'L' && t.Sym() != nil && t != Types[t.Kind()] {
+	if verb != 'L' && t.Sym() != nil && t != Types[t.Kind()] && t.Kind() != TTYPEPARAM {
 		switch mode {
 		case fmtTypeID, fmtTypeIDName:
 			if verb == 'S' {
@@ -478,6 +478,9 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 			}
 			b.WriteString("func")
 		}
+		if t.NumTParams() > 0 {
+			tconv2(b, t.TParams(), 0, mode, visited)
+		}
 		tconv2(b, t.Params(), 0, mode, visited)
 
 		switch t.NumResults() {
@@ -515,7 +518,11 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 		}
 
 		if funarg := t.StructType().Funarg; funarg != FunargNone {
-			b.WriteByte('(')
+			open, close := '(', ')'
+			if funarg == FunargTparams {
+				open, close = '[', ']'
+			}
+			b.WriteByte(byte(open))
 			fieldVerb := 'v'
 			switch mode {
 			case fmtTypeID, fmtTypeIDName, fmtGo:
@@ -528,7 +535,7 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 				}
 				fldconv(b, f, fieldVerb, mode, visited, funarg)
 			}
-			b.WriteByte(')')
+			b.WriteByte(byte(close))
 		} else {
 			b.WriteString("struct {")
 			for i, f := range t.Fields().Slice() {
@@ -554,6 +561,15 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 	case TUNSAFEPTR:
 		b.WriteString("unsafe.Pointer")
 
+	case TTYPEPARAM:
+		if t.Sym() != nil {
+			sconv2(b, t.Sym(), 'v', mode)
+		} else {
+			b.WriteString("tp")
+			// Print out the pointer value for now to disambiguate type params
+			b.WriteString(fmt.Sprintf("%p", t))
+		}
+
 	case Txxx:
 		b.WriteString("Txxx")
 

src/cmd/compile/internal/types/size.go

@@ -499,6 +499,11 @@ func CalcSize(t *Type) {
 			base.Warn("bad type %v %d\n", t1, w)
 		}
 		t.Align = 1
+
+	case TTYPEPARAM:
+		// TODO(danscales) - remove when we eliminate the need
+		// to do CalcSize in noder2 (which shouldn't be needed in the noder)
+		w = int64(PtrSize)
 	}
 
 	if PtrSize == 4 && w != int64(int32(w)) {

src/cmd/compile/internal/types/type.go

@@ -205,6 +205,7 @@ func (t *Type) Kind() Kind { return t.kind }
 
 // Sym returns the name of type t.
 func (t *Type) Sym() *Sym       { return t.sym }
+func (t *Type) SetSym(sym *Sym) { t.sym = sym }
 
 // Underlying returns the underlying type of type t.
 func (t *Type) Underlying() *Type { return t.underlying }
@@ -285,7 +286,7 @@ type Func struct {
 	Receiver *Type // function receiver
 	Results  *Type // function results
 	Params   *Type // function params
-	Tparams  *Type // type params of receiver (if method) or function
+	TParams  *Type // type params of receiver (if method) or function
 
 	pkg *Pkg
 
@@ -512,6 +513,8 @@ func New(et Kind) *Type {
 		t.Extra = new(Tuple)
 	case TRESULTS:
 		t.Extra = new(Results)
+	case TTYPEPARAM:
+		t.Extra = new(Interface)
 	}
 	return t
 }
@@ -769,10 +772,12 @@ func (t *Type) wantEtype(et Kind) {
 }
 
 func (t *Type) Recvs() *Type   { return t.FuncType().Receiver }
+func (t *Type) TParams() *Type { return t.FuncType().TParams }
 func (t *Type) Params() *Type  { return t.FuncType().Params }
 func (t *Type) Results() *Type { return t.FuncType().Results }
 
 func (t *Type) NumRecvs() int   { return t.FuncType().Receiver.NumFields() }
+func (t *Type) NumTParams() int { return t.FuncType().TParams.NumFields() }
 func (t *Type) NumParams() int  { return t.FuncType().Params.NumFields() }
 func (t *Type) NumResults() int { return t.FuncType().Results.NumFields() }
 
@@ -1648,6 +1653,15 @@ func NewInterface(pkg *Pkg, methods []*Field) *Type {
 	return t
 }
 
+// NewTypeParam returns a new type param with the given constraint (which may
+// not really be needed except for the type checker).
+func NewTypeParam(pkg *Pkg, constraint *Type) *Type {
+	t := New(TTYPEPARAM)
+	t.methods = constraint.methods
+	t.Extra.(*Interface).pkg = pkg
+	return t
+}
+
 // NewSignature returns a new function type for the given receiver,
 // parametes, results, and type parameters, any of which may be nil.
 func NewSignature(pkg *Pkg, recv *Field, tparams, params, results []*Field) *Type {
@@ -1669,7 +1683,7 @@ func NewSignature(pkg *Pkg, recv *Field, tparams, params, results []*Field) *Typ
 	}
 
 	ft.Receiver = funargs(recvs, FunargRcvr)
-	ft.Tparams = funargs(tparams, FunargTparams)
+	ft.TParams = funargs(tparams, FunargTparams)
 	ft.Params = funargs(params, FunargParams)
 	ft.Results = funargs(results, FunargResults)
 	ft.pkg = pkg

src/cmd/compile/internal/types2/type.go

@@ -837,6 +837,10 @@ type TypeParam struct {
 	aType
 }
 
+func (t *TypeParam) Obj() *TypeName {
+	return t.obj
+}
+
 // NewTypeParam returns a new TypeParam.
 func (check *Checker) NewTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
 	assert(bound != nil)