From 046e10da6483d05a0b16bea75baf8effa57a056d Mon Sep 17 00:00:00 2001
From: Teddy Wing
Date: Thu, 18 May 2023 22:21:21 +0200
Subject: Ideas for walking functions first instead of `defer`s first

I was having a hard time figuring out how to get the function where a
`defer` occurs from the defer, so I decided to look at all functions
first instead, and find out if they contain `defer`s.
---
 defererr.go | 69 +++++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 56 insertions(+), 13 deletions(-)

(limited to 'defererr.go')

diff --git a/defererr.go b/defererr.go
index d512cbf..fafb42e 100644
--- a/defererr.go
+++ b/defererr.go
@@ -24,33 +24,76 @@ func run(pass *analysis.Pass) (interface{}, error) {
 		ast.Inspect(
 			file,
 			func(node ast.Node) bool {
-				deferStmt, ok := node.(*ast.DeferStmt)
+				funcType, ok := node.(*ast.FuncType)
 				if !ok {
 					return true
 				}
 
-				// Look for a function literal after the `defer` statement.
-				funcLit, ok := deferStmt.Call.Fun.(*ast.FuncLit)
-				if !ok {
+				if funcType.Results == nil {
 					return true
 				}
 
-				funcScope := pass.TypesInfo.Scopes[funcLit.Type]
+				funcReturnsError := false
+				for _, returnVal := range funcType.Results.List {
+					fmt.Printf("returnVal: %#v\n", returnVal.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 {
+					returnIdent, ok := returnVal.Type.(*ast.Ident)
+					if !ok {
 					return true
+					}
+
+					if returnIdent.Name == "error" {
+						funcReturnsError = true
+					}
 				}
-				fmt.Printf("func: %#v\n", funcType)
 
-				if funcLit.Type.Results == nil {
+				// Can we do the same for non-error types?
+				// for _, returnVal := range funcType.Results.List {
+				// }
+
+				if !funcReturnsError {
 					return true
 				}
 
-				for _, returnVal := range funcLit.Type.Results.List {
-					fmt.Printf("returnVal: %#v\n", returnVal)
-				}
+				ast.Inspect(
+					funcType,
+					func(node ast.Node) bool {
+						fmt.Printf("node: %#v\n", node)
+						deferStmt, ok := node.(*ast.DeferStmt)
+						if !ok {
+							return true
+						}
+
+						fmt.Printf("defer: %#v\n", deferStmt)
+
+						// TODO: Find out if defer uses assigns an error variable without declaring it
+
+						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
 			},
-- 
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