ifelse: option to preserve variable scope (#832)

* ifelse: option to preserve variable scope

testdata/early-return-scope.go

@@ -0,0 +1,66 @@
+// Test data for the early-return rule with preserveScope option enabled
+
+package fixtures
+
+func fn1() {
+	// No initializer, match as normal
+	if cond { //   MATCH /if c { ... } else { ... return } can be simplified to if !c { ... return } .../
+		fn2()
+	} else {
+		return
+	}
+}
+
+func fn2() {
+	// Moving the declaration of x here is fine since it goes out of scope either way
+	if x := fn1(); x != nil { //   MATCH /if c { ... } else { ... return } can be simplified to if !c { ... return } ... (move short variable declaration to its own line if necessary)/
+		fn2()
+	} else {
+		return
+	}
+}
+
+func fn3() {
+	// Don't want to move the declaration of x here since it stays in scope afterward
+	if x := fn1(); x != nil {
+		fn2()
+	} else {
+		return
+	}
+	x := fn2()
+	fn3(x)
+}
+
+func fn4() {
+	if cond {
+		var x = fn2()
+		fn3(x)
+	} else {
+		return
+	}
+	// Don't want to move the declaration of x here since it stays in scope afterward
+	y := fn2()
+	fn3(y)
+}
+
+func fn5() {
+	if cond {
+		x := fn2()
+		fn3(x)
+	} else {
+		return
+	}
+	// Don't want to move the declaration of x here since it stays in scope afterward
+	y := fn2()
+	fn3(y)
+}
+
+func fn6() {
+	if cond { //   MATCH /if c { ... } else { ... return } can be simplified to if !c { ... return } .../
+		x := fn2()
+		fn3(x)
+	} else {
+		return
+	}
+	// Moving x here is fine since it goes out of scope anyway
+}