compiler: allow to use exported variables

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/compiler/compiler.go

@@ -49,11 +49,29 @@ func (c *codegen) ForEachFile(fn func(*ast.File, *types.Package)) {
 	for _, pkg := range c.buildInfo.program.AllPackages {
 		c.typeInfo = &pkg.Info
 		for _, f := range pkg.Files {
+			c.fillImportMap(f, pkg.Pkg)
 			fn(f, pkg.Pkg)
 		}
 	}
 }
 
+// fillImportMap fills import map for f.
+func (c *codegen) fillImportMap(f *ast.File, pkg *types.Package) {
+	c.importMap = map[string]string{"": pkg.Path()}
+	for _, imp := range f.Imports {
+		// We need to load find package metadata because
+		// name specified in `package ...` decl, can be in
+		// conflict with package path.
+		pkgPath := strings.Trim(imp.Path.Value, `"`)
+		realPkg := c.buildInfo.program.Package(pkgPath)
+		name := realPkg.Pkg.Name()
+		if imp.Name != nil {
+			name = imp.Name.Name
+		}
+		c.importMap[name] = realPkg.Pkg.Path()
+	}
+}
+
 func getBuildInfo(src interface{}) (*buildInfo, error) {
 	conf := loader.Config{ParserMode: parser.ParseComments}
 	f, err := conf.ParseFile("", src)