Example #1
0
// VarValue returns the SSA Value that corresponds to a specific
// identifier denoting the source-level named variable obj.
//
// VarValue returns nil if a local variable was not found, perhaps
// because its package was not built, the debug information was not
// requested during SSA construction, or the value was optimized away.
//
// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
// and that ident must resolve to obj.
//
// pkg is the package enclosing the reference.  (A reference to a var
// may result in code, so we need to know where to find that code.)
//
// The Value of a defining (as opposed to referring) identifier is the
// value assigned to it in its definition.
//
// In many cases where the identifier appears in an lvalue context,
// the resulting Value is the var's address, not its value.
// For example, x in all these examples:
//    x.y = 0
//    x[0] = 0
//    _ = x[:]
//    x = X{}
//    _ = &x
//    x.method()    (iff method is on &x)
// and all package-level vars.  (This situation can be detected by
// comparing the types of the Var and Value.)
//
func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) Value {
	id := ref[0].(*ast.Ident)

	// Package-level variable?
	if v := prog.packageLevelValue(obj); v != nil {
		return v.(*Global)
	}

	// Must be a function-local variable.
	// (e.g. local, parameter, or field selection e.f)
	fn := EnclosingFunction(pkg, ref)
	if fn == nil {
		return nil // e.g. SSA not built
	}

	// Defining ident of a parameter?
	if id.Pos() == obj.Pos() {
		for _, param := range fn.Params {
			if param.Object() == obj {
				return param
			}
		}
	}

	// Other ident?
	for _, b := range fn.Blocks {
		for _, instr := range b.Instrs {
			if ref, ok := instr.(*DebugRef); ok {
				if ref.Pos() == id.Pos() {
					return ref.X
				}
			}
		}
	}

	return nil // e.g. debug info not requested, or var optimized away
}
Example #2
0
// VarValue returns the SSA Value that corresponds to a specific
// identifier denoting the source-level named variable obj.
//
// VarValue returns nil if a local variable was not found, perhaps
// because its package was not built, the debug information was not
// requested during SSA construction, or the value was optimized away.
//
// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
// and that ident must resolve to obj.
//
// pkg is the package enclosing the reference.  (A reference to a var
// always occurs within a function, so we need to know where to find it.)
//
// The Value of a defining (as opposed to referring) identifier is the
// value assigned to it in its definition.  Similarly, the Value of an
// identifier that is the LHS of an assignment is the value assigned
// to it in that statement.  In all these examples, VarValue(x) returns
// the value of x and isAddr==false.
//
//    var x X
//    var x = X{}
//    x := X{}
//    x = X{}
//
// When an identifier appears in an lvalue context other than as the
// LHS of an assignment, the resulting Value is the var's address, not
// its value.  This situation is reported by isAddr, the second
// component of the result.  In these examples, VarValue(x) returns
// the address of x and isAddr==true.
//
//    x.y = 0
//    x[0] = 0
//    _ = x[:]      (where x is an array)
//    _ = &x
//    x.method()    (iff method is on &x)
//
func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) (value Value, isAddr bool) {
	// All references to a var are local to some function, possibly init.
	fn := EnclosingFunction(pkg, ref)
	if fn == nil {
		return // e.g. def of struct field; SSA not built?
	}

	id := ref[0].(*ast.Ident)

	// Defining ident of a parameter?
	if id.Pos() == obj.Pos() {
		for _, param := range fn.Params {
			if param.Object() == obj {
				return param, false
			}
		}
	}

	// Other ident?
	for _, b := range fn.Blocks {
		for _, instr := range b.Instrs {
			if dr, ok := instr.(*DebugRef); ok {
				if dr.Pos() == id.Pos() {
					return dr.X, dr.IsAddr
				}
			}
		}
	}

	// Defining ident of package-level var?
	if v := prog.packageLevelValue(obj); v != nil {
		return v.(*Global), true
	}

	return // e.g. debug info not requested, or var optimized away
}
Example #3
0
// checkStructField checks that the field renaming will not cause
// conflicts at its declaration, or ambiguity or changes to any selection.
func (r *renamer) checkStructField(from *types.Var) {
	// Check that the struct declaration is free of field conflicts,
	// and field/method conflicts.

	// go/types offers no easy way to get from a field (or interface
	// method) to its declaring struct (or interface), so we must
	// ascend the AST.
	info, path, _ := r.iprog.PathEnclosingInterval(from.Pos(), from.Pos())
	// path is [Ident Field FieldList StructType ... File].  Can't fail.

	// Ascend past parens (unlikely).
	i := 4
	for {
		_, ok := path[i].(*ast.ParenExpr)
		if !ok {
			break
		}
		i++
	}
	if spec, ok := path[i].(*ast.TypeSpec); ok {
		// This struct is also a named type.
		// We must check for direct (non-promoted) field/field
		// and method/field conflicts.
		named := info.Defs[spec.Name].Type()
		prev, indices, _ := types.LookupFieldOrMethod(named, true, info.Pkg, r.to)
		if len(indices) == 1 {
			r.errorf(from.Pos(), "renaming this field %q to %q",
				from.Name(), r.to)
			r.errorf(prev.Pos(), "\twould conflict with this %s",
				objectKind(prev))
			return // skip checkSelections to avoid redundant errors
		}
	} else {
		// This struct is not a named type.
		// We need only check for direct (non-promoted) field/field conflicts.
		T := info.Types[path[3].(*ast.StructType)].Type.Underlying().(*types.Struct)
		for i := 0; i < T.NumFields(); i++ {
			if prev := T.Field(i); prev.Name() == r.to {
				r.errorf(from.Pos(), "renaming this field %q to %q",
					from.Name(), r.to)
				r.errorf(prev.Pos(), "\twould conflict with this field")
				return // skip checkSelections to avoid redundant errors
			}
		}
	}

	// Renaming an anonymous field requires renaming the type too. e.g.
	// 	print(s.T)       // if we rename T to U,
	// 	type T int       // this and
	// 	var s struct {T} // this must change too.
	if from.Anonymous() {
		if named, ok := from.Type().(*types.Named); ok {
			r.check(named.Obj())
		} else if named, ok := deref(from.Type()).(*types.Named); ok {
			r.check(named.Obj())
		}
	}

	// Check integrity of existing (field and method) selections.
	r.checkSelections(from)
}