Major rework of codebase

- Get rid of 'core' and move CLI to cmd/gas directory
- Migrate (most) tests to use Ginkgo and testutils framework
- GAS now expects package to reside in $GOPATH
- GAS now can resolve dependencies for better type checking (if package
  on GOPATH)
- Simplified public API

resolve_test.go

@@ -0,0 +1,95 @@
+package gas_test
+
+import (
+	"go/ast"
+
+	"github.com/GoASTScanner/gas"
+	"github.com/GoASTScanner/gas/testutils"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Resolve ast node to concrete value", func() {
+	Context("when attempting to resolve an ast node", func() {
+		It("should successfully resolve basic literal", func() {
+			var basicLiteral *ast.BasicLit
+
+			pkg := testutils.NewTestPackage()
+			pkg.AddFile("foo.go", `package main; const foo = "bar"; func main(){}`)
+			ctx := pkg.CreateContext("foo.go")
+			v := testutils.NewMockVisitor()
+			v.Callback = func(n ast.Node, ctx *gas.Context) bool {
+				if node, ok := n.(*ast.BasicLit); ok {
+					basicLiteral = node
+					return false
+				}
+				return true
+			}
+			v.Context = ctx
+			ast.Walk(v, ctx.Root)
+			Expect(basicLiteral).ShouldNot(BeNil())
+			Expect(gas.TryResolve(basicLiteral, ctx)).Should(BeTrue())
+		})
+
+		It("should successfully resolve identifier", func() {
+			var ident *ast.Ident
+			pkg := testutils.NewTestPackage()
+			pkg.AddFile("foo.go", `package main; var foo string = "bar"; func main(){}`)
+			ctx := pkg.CreateContext("foo.go")
+			v := testutils.NewMockVisitor()
+			v.Callback = func(n ast.Node, ctx *gas.Context) bool {
+				if node, ok := n.(*ast.Ident); ok {
+					ident = node
+					return false
+				}
+				return true
+			}
+			v.Context = ctx
+			ast.Walk(v, ctx.Root)
+			Expect(ident).ShouldNot(BeNil())
+			Expect(gas.TryResolve(ident, ctx)).Should(BeTrue())
+		})
+
+		It("should successfully resolve assign statement", func() {
+			var assign *ast.AssignStmt
+			pkg := testutils.NewTestPackage()
+			pkg.AddFile("foo.go", `package main; const x = "bar"; func main(){ y := x; println(y) }`)
+			ctx := pkg.CreateContext("foo.go")
+			v := testutils.NewMockVisitor()
+			v.Callback = func(n ast.Node, ctx *gas.Context) bool {
+				if node, ok := n.(*ast.AssignStmt); ok {
+					if id, ok := node.Lhs[0].(*ast.Ident); ok && id.Name == "y" {
+						assign = node
+					}
+				}
+				return true
+			}
+			v.Context = ctx
+			ast.Walk(v, ctx.Root)
+			Expect(assign).ShouldNot(BeNil())
+			Expect(gas.TryResolve(assign, ctx)).Should(BeTrue())
+		})
+
+		It("should successfully resolve a binary statement", func() {
+			var target *ast.BinaryExpr
+			pkg := testutils.NewTestPackage()
+			pkg.AddFile("foo.go", `package main; const (x = "bar"; y = "baz"); func main(){ z := x + y; println(z) }`)
+			ctx := pkg.CreateContext("foo.go")
+			v := testutils.NewMockVisitor()
+			v.Callback = func(n ast.Node, ctx *gas.Context) bool {
+				if node, ok := n.(*ast.BinaryExpr); ok {
+					target = node
+				}
+				return true
+			}
+			v.Context = ctx
+			ast.Walk(v, ctx.Root)
+			Expect(target).ShouldNot(BeNil())
+			Expect(gas.TryResolve(target, ctx)).Should(BeTrue())
+		})
+
+		// TODO: It should resolve call expressions
+
+	})
+
+})