gotypes: doc exported symbols (#9)

gotypes/components.go

@@ -10,24 +10,35 @@ import (
 	"github.com/mmcloughlin/avo/operand"
 )
 
+// Sizes provides type sizes used by the standard Go compiler on amd64.
 var Sizes = types.SizesFor("gc", "amd64")
 
+// Basic represents a primitive/basic type at a given memory address.
 type Basic struct {
 	Addr operand.Mem
 	Type *types.Basic
 }
 
+// Component provides access to sub-components of a Go type.
 type Component interface {
+	// When the component has no further sub-components, Resolve will return a
+	// reference to the components type and memory address. If there was an error
+	// during any previous calls to Component methods, they will be returned at
+	// resolution time.
 	Resolve() (*Basic, error)
-	Base() Component
-	Len() Component
-	Cap() Component
-	Real() Component
-	Imag() Component
-	Index(int) Component
-	Field(string) Component
+
+	Base() Component        // base pointer of a string or slice
+	Len() Component         // length of a string or slice
+	Cap() Component         // capacity of a slice
+	Real() Component        // real part of a complex value
+	Imag() Component        // imaginary part of a complex value
+	Index(int) Component    // index into an array
+	Field(string) Component // access a struct field
 }
 
+// componenterr is an error that also provides a null implementation of the
+// Component interface. This enables us to return an error from Component
+// methods whilst also allowing method chaining to continue.
 type componenterr string
 
 func errorf(format string, args ...interface{}) Component {
@@ -50,6 +61,7 @@ type component struct {
 	offset int
 }
 
+// NewComponent builds a component for the named type at the given memory offset.
 func NewComponent(name string, t types.Type, offset int) Component {
 	return &component{
 		name:   name,
@@ -58,10 +70,6 @@ func NewComponent(name string, t types.Type, offset int) Component {
 	}
 }
 
-func NewComponentFromVar(v *types.Var, offset int) Component {
-	return NewComponent(v.Name(), v.Type(), offset)
-}
-
 func (c *component) Resolve() (*Basic, error) {
 	b := toprimitive(c.typ)
 	if b == nil {

gotypes/doc.go

@@ -0,0 +1,2 @@
+// Package gotypes provides helpers for interacting with Go types within avo functions.
+package gotypes

gotypes/examples_test.go

@@ -0,0 +1,16 @@
+package gotypes_test
+
+import (
+	"fmt"
+
+	"github.com/mmcloughlin/avo/gotypes"
+)
+
+func ExampleParseSignature() {
+	s, err := gotypes.ParseSignature("func(s string, n int) string")
+	fmt.Println(s)
+	fmt.Println(err)
+	// Output:
+	// (s string, n int) string
+	// <nil>
+}

gotypes/signature.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 )
 
+// Signature represents a Go function signature.
 type Signature struct {
 	pkg     *types.Package
 	sig     *types.Signature
@@ -15,6 +16,7 @@ type Signature struct {
 	results *Tuple
 }
 
+// NewSignature constructs a Signature.
 func NewSignature(pkg *types.Package, sig *types.Signature) *Signature {
 	s := &Signature{
 		pkg: pkg,
@@ -24,14 +26,20 @@ func NewSignature(pkg *types.Package, sig *types.Signature) *Signature {
 	return s
 }
 
+// NewSignatureVoid builds the void signature "func()".
 func NewSignatureVoid() *Signature {
 	return NewSignature(nil, types.NewSignature(nil, nil, nil, false))
 }
 
+// ParseSignature builds a Signature by parsing a Go function type expression.
+// The function type must reference builtin types only; see
+// ParseSignatureInPackage if custom types are required.
 func ParseSignature(expr string) (*Signature, error) {
 	return ParseSignatureInPackage(nil, expr)
 }
 
+// ParseSignatureInPackage builds a Signature by parsing a Go function type
+// expression. The expression may reference types in the provided package.
 func ParseSignatureInPackage(pkg *types.Package, expr string) (*Signature, error) {
 	tv, err := types.Eval(token.NewFileSet(), pkg, token.NoPos, expr)
 	if err != nil {
@@ -47,12 +55,16 @@ func ParseSignatureInPackage(pkg *types.Package, expr string) (*Signature, error
 	return NewSignature(pkg, s), nil
 }
 
+// Params returns the function signature argument types.
 func (s *Signature) Params() *Tuple { return s.params }
 
+// Results returns the function return types.
 func (s *Signature) Results() *Tuple { return s.results }
 
+// Bytes returns the total size of the function arguments and return values.
 func (s *Signature) Bytes() int { return s.Params().Bytes() + s.Results().Bytes() }
 
+// String writes Signature as a string. This does not include the "func" keyword.
 func (s *Signature) String() string {
 	var buf bytes.Buffer
 	types.WriteSignature(&buf, s.sig, types.RelativeTo(s.pkg))
@@ -83,6 +95,7 @@ func (s *Signature) init() {
 	s.results = newTuple(r, resultsoffsets, resultssize, "ret")
 }
 
+// Tuple represents a tuple of variables, such as function arguments or results.
 type Tuple struct {
 	components []Component
 	byname     map[string]Component
@@ -112,6 +125,7 @@ func newTuple(t *types.Tuple, offsets []int64, size int64, defaultprefix string)
 	return tuple
 }
 
+// Lookup returns the variable with the given name.
 func (t *Tuple) Lookup(name string) Component {
 	e := t.byname[name]
 	if e == nil {
@@ -120,6 +134,7 @@ func (t *Tuple) Lookup(name string) Component {
 	return e
 }
 
+// At returns the variable at index i.
 func (t *Tuple) At(i int) Component {
 	if i >= len(t.components) {
 		return errorf("index out of range")
@@ -127,6 +142,7 @@ func (t *Tuple) At(i int) Component {
 	return t.components[i]
 }
 
+// Bytes returns the size of the Tuple. This may include additional padding.
 func (t *Tuple) Bytes() int { return t.size }
 
 func tuplevars(t *types.Tuple) []*types.Var {