Ideas for an analyser for returning errors from defer

Still working out how to traverse the AST to be able to see the objects
I need.

1 files changed, 61 insertions, 0 deletions

diff --git a/defererr.go b/defererr.go
new file mode 100644
index 0000000..d512cbf
--- /dev/null
+++ b/defererr.go
@@ -0,0 +1,61 @@
+// TODO: doc
+package defererr
+
+import (
+	"fmt"
+	"go/ast"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var Analyzer = &analysis.Analyzer{
+	Name: "defererr",
+	Doc:  "reports issues returning errors from defer",
+	Run:  run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	// TODO: Find defer closure
+	// Does it set error defined in outer scope?
+	// Does outer scope declare error variable in signature?
+	// Is err variable returned after closure?
+
+	for _, file := range pass.Files {
+		ast.Inspect(
+			file,
+			func(node ast.Node) bool {
+				deferStmt, ok := node.(*ast.DeferStmt)
+				if !ok {
+					return true
+				}
+
+				// Look for a function literal after the `defer` statement.
+				funcLit, ok := deferStmt.Call.Fun.(*ast.FuncLit)
+				if !ok {
+					return true
+				}
+
+				funcScope := pass.TypesInfo.Scopes[funcLit.Type]
+
+				// Try to find the function where the defer is defined. Note, defer can be defined in an inner block.
+				funcType, ok := funcScope.Parent().(*ast.FuncType)
+				if !ok {
+					return true
+				}
+				fmt.Printf("func: %#v\n", funcType)
+
+				if funcLit.Type.Results == nil {
+					return true
+				}
+
+				for _, returnVal := range funcLit.Type.Results.List {
+					fmt.Printf("returnVal: %#v\n", returnVal)
+				}
+
+				return true
+			},
+		)
+	}
+
+	return nil, nil
+}