go.tools/ssa: remove position info from Literals.

R=gri
CC=golang-dev
https://golang.org/cl/11292043

ssa/builder.go

@@ -57,8 +57,8 @@ var (
 	// SSA Value constants.
 	vZero  = intLiteral(0)
 	vOne   = intLiteral(1)
-	vTrue  = NewLiteral(exact.MakeBool(true), tBool, token.NoPos)
+	vTrue  = NewLiteral(exact.MakeBool(true), tBool)
-	vFalse = NewLiteral(exact.MakeBool(false), tBool, token.NoPos)
+	vFalse = NewLiteral(exact.MakeBool(false), tBool)
 )
 
 // builder holds state associated with the package currently being built.
@@ -547,12 +547,7 @@ func (b *builder) exprInPlace(fn *Function, loc lvalue, e ast.Expr) {
 //
 func (b *builder) expr(fn *Function, e ast.Expr) Value {
 	if v := fn.Pkg.info.ValueOf(e); v != nil {
-		// TODO(adonovan): if e is an ident referring to a named
+		lit := NewLiteral(v, fn.Pkg.typeOf(e))
-		// Const, should we share the Constant's literal?
-		// Then it won't have a position within the function.
-		// Do we want it to have the position of the Ident or
-		// the definition of the const expression?
-		lit := NewLiteral(v, fn.Pkg.typeOf(e), CanonicalPos(e))
 		if id, ok := unparen(e).(*ast.Ident); ok {
 			emitDebugRef(fn, id, lit)
 		}

ssa/create.go

@@ -91,7 +91,7 @@ func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node) {
 	case *types.Const:
 		c := &Constant{
 			object: obj,
-			Value:  NewLiteral(obj.Val(), obj.Type(), obj.Pos()),
+			Value:  NewLiteral(obj.Val(), obj.Type()),
 		}
 		pkg.values[obj] = c.Value
 		pkg.Members[name] = c

ssa/emit.go

@@ -210,7 +210,7 @@ func emitConv(f *Function, val Value, typ types.Type) Value {
 	// change yet; this defers the point at which the number of
 	// possible representations explodes.
 	if l, ok := val.(*Literal); ok {
-		return NewLiteral(l.Value, typ, l.Pos())
+		return NewLiteral(l.Value, typ)
 	}
 
 	// A representation-changing conversion.

ssa/interp/ops.go

@@ -159,6 +159,10 @@ func zero(t types.Type) value {
 			panic("untyped nil has no zero value")
 		}
 		if t.Info()&types.IsUntyped != 0 {
+			// TODO(adonovan): make it an invariant that
+			// this is unreachable.  Currently some
+			// literals have 'untyped' types when they
+			// should be defaulted by the typechecker.
 			t = ssa.DefaultType(t).(*types.Basic)
 		}
 		switch t.Kind() {

ssa/literal.go

@@ -11,23 +11,23 @@ import (
 	"code.google.com/p/go.tools/go/types"
 )
 
-// NewLiteral returns a new literal of the specified value, type and position.
+// NewLiteral returns a new literal of the specified value and type.
 // val must be valid according to the specification of Literal.Value.
 //
-func NewLiteral(val exact.Value, typ types.Type, pos token.Pos) *Literal {
+func NewLiteral(val exact.Value, typ types.Type) *Literal {
-	return &Literal{typ, val, pos}
+	return &Literal{typ, val}
 }
 
 // intLiteral returns an untyped integer literal that evaluates to i.
 func intLiteral(i int64) *Literal {
-	return NewLiteral(exact.MakeInt64(i), types.Typ[types.UntypedInt], token.NoPos)
+	return NewLiteral(exact.MakeInt64(i), types.Typ[types.UntypedInt])
 }
 
 // nilLiteral returns a nil literal of the specified type, which may
 // be any reference type, including interfaces.
 //
 func nilLiteral(typ types.Type) *Literal {
-	return NewLiteral(exact.MakeNil(), typ, token.NoPos)
+	return NewLiteral(exact.MakeNil(), typ)
 }
 
 // zeroLiteral returns a new "zero" literal of the specified type,
@@ -39,11 +39,11 @@ func zeroLiteral(t types.Type) *Literal {
 	case *types.Basic:
 		switch {
 		case t.Info()&types.IsBoolean != 0:
-			return NewLiteral(exact.MakeBool(false), t, token.NoPos)
+			return NewLiteral(exact.MakeBool(false), t)
 		case t.Info()&types.IsNumeric != 0:
-			return NewLiteral(exact.MakeInt64(0), t, token.NoPos)
+			return NewLiteral(exact.MakeInt64(0), t)
 		case t.Info()&types.IsString != 0:
-			return NewLiteral(exact.MakeString(""), t, token.NoPos)
+			return NewLiteral(exact.MakeString(""), t)
 		case t.Kind() == types.UnsafePointer:
 			fallthrough
 		case t.Kind() == types.UntypedNil:
@@ -54,7 +54,7 @@ func zeroLiteral(t types.Type) *Literal {
 	case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
 		return nilLiteral(t)
 	case *types.Named:
-		return NewLiteral(zeroLiteral(t.Underlying()).Value, t, token.NoPos)
+		return NewLiteral(zeroLiteral(t.Underlying()).Value, t)
 	case *types.Array, *types.Struct:
 		panic(fmt.Sprint("zeroLiteral applied to aggregate:", t))
 	}
@@ -85,7 +85,7 @@ func (l *Literal) Referrers() *[]Instruction {
 }
 
 func (l *Literal) Pos() token.Pos {
-	return l.pos
+	return token.NoPos
 }
 
 // IsNil returns true if this literal represents a typed or untyped nil value.

ssa/source.go

@@ -37,9 +37,9 @@ func (prog *Program) PathEnclosingInterval(imp *importer.Importer, start, end to
 				continue
 			}
 			if path, exact := PathEnclosingInterval(f, start, end); path != nil {
-				// TODO(adonovan): return the
+				// TODO(adonovan): return info in lieu
-				// importPath; remove Prog as a
+				// of pkg; remove Prog as a parameter;
-				// parameter.
+				// move to importer.
 				return prog.PackagesByPath[importPath], path, exact
 			}
 		}
@@ -171,24 +171,21 @@ func CanonicalPos(n ast.Node) token.Pos {
 		return CanonicalPos(n.X)
 
 	case *ast.CallExpr:
-		// f(x):    *Call, *Go, *Defer, *Literal (e.g. len)
+		// f(x):    *Call, *Go, *Defer.
-		// T(x):    *ChangeType, *Convert, *MakeInterface, *ChangeInterface, *Literal.
+		// T(x):    *ChangeType, *Convert, *MakeInterface, *ChangeInterface.
 		// make():  *MakeMap, *MakeChan, *MakeSlice.
 		// new():   *Alloc.
 		// panic(): *Panic.
 		return n.Lparen
 
-	case *ast.BasicLit:
-		return n.ValuePos // *Literal
-
 	case *ast.Ident:
-		return n.NamePos // *Parameter, *Alloc, *Capture, *Literal
+		return n.NamePos // *Parameter, *Alloc, *Capture
 
 	case *ast.TypeAssertExpr:
 		return n.Lparen // *ChangeInterface or *TypeAssertExpr
 
 	case *ast.SelectorExpr:
-		return n.Sel.NamePos // *MakeClosure, *Field, *FieldAddr, *Literal
+		return n.Sel.NamePos // *MakeClosure, *Field, *FieldAddr
 
 	case *ast.FuncLit:
 		return n.Type.Func // *Function or *MakeClosure
@@ -197,10 +194,10 @@ func CanonicalPos(n ast.Node) token.Pos {
 		return n.Lbrace // *Alloc or *Slice
 
 	case *ast.BinaryExpr:
-		return n.OpPos // *Phi, *BinOp or *Literal
+		return n.OpPos // *Phi or *BinOp
 
 	case *ast.UnaryExpr:
-		return n.OpPos // *Phi, *UnOp, or *Literal
+		return n.OpPos // *Phi or *UnOp
 
 	case *ast.IndexExpr:
 		return n.Lbrack // *Index or *IndexAddr
@@ -277,25 +274,18 @@ func (prog *Program) FuncValue(obj *types.Func) Value {
 // constant obj.  The result may be a *Literal, or nil if not found.
 //
 func (prog *Program) ConstValue(obj *types.Const) *Literal {
+	// TODO(adonovan): opt: share (don't reallocate)
+	// Literals for const objects.
+
 	// Universal constant? {true,false,nil}
 	if obj.Parent() == types.Universe {
-		// TODO(adonovan): opt: share, don't reallocate.
+		return NewLiteral(obj.Val(), obj.Type())
-		return NewLiteral(obj.Val(), obj.Type(), obj.Pos())
 	}
 	// Package-level named constant?
 	if v := prog.packageLevelValue(obj); v != nil {
 		return v.(*Literal)
 	}
-	// TODO(adonovan): need a per-function const object map.  For
+	return NewLiteral(obj.Val(), obj.Type())
-	// now, just return a new literal.
-	//
-	// Design question: should literal (constant) values even have
-	// a position?  Is their identity important?  Should two
-	// different references to Math.pi be distinguishable in any
-	// way?  From an analytical perspective, their type and value
-	// tell you all you need to know; they're interchangeable.
-	// Experiment with removing Literal.Pos().
-	return NewLiteral(obj.Val(), obj.Type(), obj.Pos())
 }
 
 // VarValue returns the SSA Value that corresponds to a specific

ssa/source_ast.go

@@ -4,7 +4,7 @@ package ssa
 
 // It has no dependencies on ssa or go/types.
 // TODO(adonovan): move it somewhere more general,
-// e.g. go.tools/astutil?
+// e.g. go.tools/importer?
 
 import (
 	"fmt"

ssa/source_test.go

@@ -299,7 +299,6 @@ func TestObjValueLookup(t *testing.T) {
 	for _, c := range f.Comments {
 		text := c.Text()
 		pos := imp.Fset.Position(c.Pos())
-		fmt.Println(pos.Line, text)
 		for _, m := range re.FindAllStringSubmatch(text, -1) {
 			key := fmt.Sprintf("%s:%d", m[2], pos.Line)
 			value := m[1] + m[3]

ssa/ssa.go

@@ -377,8 +377,7 @@ type Parameter struct {
 // Type(), using the same representation as package go/exact uses for
 // constants.
 //
-// Pos() returns the canonical position (see CanonicalPos) of the
+// Pos() returns token.NoPos.
-// originating constant expression, if explicit in the source.
 //
 // Example printed form:
 // 	42:int
@@ -388,7 +387,6 @@ type Parameter struct {
 type Literal struct {
 	typ   types.Type
 	Value exact.Value
-	pos   token.Pos
 }
 
 // A Global is a named Value holding the address of a package-level
@@ -1165,7 +1163,7 @@ type DebugRef struct {
 // Register is a mix-in embedded by all SSA values that are also
 // instructions, i.e. virtual registers, and provides implementations
 // of the Value interface's Name() and Type() methods: the name is
-// simply a numbered register (e.g. "t0") and the type is the Type_
+// simply a numbered register (e.g. "t0") and the type is the typ
 // field.
 //
 // Temporary names are automatically assigned to each Register on