gotypes: add missing Underlying() calls (#78)

Issue #77 pointed out that in the case of named array types, the gotypes Components type fails to recognize the underlying type as an array. In fact this problem was more widespread. This diff fixes the missing calls to Underlying() and adds some test cases.

Fixes #77

gotypes/components_test.go

@@ -1,6 +1,7 @@
 package gotypes
 
 import (
+	"go/token"
 	"go/types"
 	"strings"
 	"testing"
@@ -96,3 +97,132 @@ func TestComponentErrorChaining(t *testing.T) {
 		}
 	}
 }
+
+func TestComponentDeconstruction(t *testing.T) {
+	cases := []struct {
+		Name   string
+		Type   types.Type
+		Chain  func(Component) Component
+		Param  string
+		Offset int
+	}{
+		{
+			Name:   "slice_base",
+			Type:   types.NewSlice(types.Typ[types.Uint64]),
+			Chain:  func(c Component) Component { return c.Base() },
+			Param:  "base",
+			Offset: 0,
+		},
+		{
+			Name:   "slice_len",
+			Type:   types.NewSlice(types.Typ[types.Uint64]),
+			Chain:  func(c Component) Component { return c.Len() },
+			Param:  "len",
+			Offset: 8,
+		},
+		{
+			Name:   "slice_cap",
+			Type:   types.NewSlice(types.Typ[types.Uint64]),
+			Chain:  func(c Component) Component { return c.Cap() },
+			Param:  "cap",
+			Offset: 16,
+		},
+		{
+			Name:   "string_base",
+			Type:   types.Typ[types.String],
+			Chain:  func(c Component) Component { return c.Base() },
+			Param:  "base",
+			Offset: 0,
+		},
+		{
+			Name:   "slice_len",
+			Type:   types.Typ[types.String],
+			Chain:  func(c Component) Component { return c.Len() },
+			Param:  "len",
+			Offset: 8,
+		},
+		{
+			Name:   "complex64_real",
+			Type:   types.Typ[types.Complex64],
+			Chain:  func(c Component) Component { return c.Real() },
+			Param:  "real",
+			Offset: 0,
+		},
+		{
+			Name:   "complex64_imag",
+			Type:   types.Typ[types.Complex64],
+			Chain:  func(c Component) Component { return c.Imag() },
+			Param:  "imag",
+			Offset: 4,
+		},
+		{
+			Name:   "complex128_real",
+			Type:   types.Typ[types.Complex128],
+			Chain:  func(c Component) Component { return c.Real() },
+			Param:  "real",
+			Offset: 0,
+		},
+		{
+			Name:   "complex128_imag",
+			Type:   types.Typ[types.Complex128],
+			Chain:  func(c Component) Component { return c.Imag() },
+			Param:  "imag",
+			Offset: 8,
+		},
+		{
+			Name:   "array",
+			Type:   types.NewArray(types.Typ[types.Uint32], 7),
+			Chain:  func(c Component) Component { return c.Index(3) },
+			Param:  "3",
+			Offset: 12,
+		},
+		{
+			Name: "struct",
+			Type: types.NewStruct([]*types.Var{
+				types.NewField(token.NoPos, nil, "Byte", types.Typ[types.Byte], false),
+				types.NewField(token.NoPos, nil, "Uint64", types.Typ[types.Uint64], false),
+			}, nil),
+			Chain:  func(c Component) Component { return c.Field("Uint64") },
+			Param:  "Uint64",
+			Offset: 8,
+		},
+	}
+
+	// For every test case, generate the same case but when the type is wrapped in
+	// a named type.
+	n := len(cases)
+	for i := 0; i < n; i++ {
+		wrapped := cases[i]
+		wrapped.Name += "_wrapped"
+		wrapped.Type = types.NewNamed(
+			types.NewTypeName(token.NoPos, nil, "wrapped", nil),
+			wrapped.Type,
+			nil,
+		)
+		cases = append(cases, wrapped)
+	}
+
+	for _, c := range cases {
+		c := c // avoid scopelint error
+		t.Run(c.Name, func(t *testing.T) {
+			t.Log(c.Type)
+			base := operand.NewParamAddr("test", 0)
+			comp := NewComponent(c.Type, base)
+			comp = c.Chain(comp)
+
+			b, err := comp.Resolve()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			expectname := "test_" + c.Param
+			if b.Addr.Symbol.Name != expectname {
+				t.Errorf("parameter name %q; expected %q", b.Addr.Symbol.Name, expectname)
+			}
+
+			if b.Addr.Disp != c.Offset {
+				t.Errorf("offset %d; expected %d", b.Addr.Disp, c.Offset)
+			}
+		})
+	}
+}