test: add testcases for directives and add comments for clarity

analyzer/testdata/src/i/directives.go

@@ -1,15 +1,45 @@
 package i
 
+func excludedConsumer(e TestExcluded) string {
+	return e.A
+}
+
 func shouldNotFailOnIgnoreDirective() (Test, error) {
+	// directive on previous line
+	//exhaustruct:ignore
+	_ = Test2{}
+
+	// directive at the end of the line
+	_ = Test{} //exhaustruct:ignore
+
+	// some style weirdness
+	_ =
+		//exhaustruct:ignore
+		Test3{
+			B: 0,
+		}
+
+	// directive after the literal
+	_ = Test{
+		B: 0,
+	} //exhaustruct:ignore
+
 	//exhaustruct:ignore
 	return Test{}, nil
 }
 
-func shouldNotFailOnIgnoreDirectivePlacedOnEOL() (Test, error) {
-	return Test{}, nil //exhaustruct:ignore
-}
+func shouldFailOnExcludedButEnforced() {
+	// directive on previous line associated with different ast leaf
+	//exhaustruct:enforce
+	_ = excludedConsumer(TestExcluded{B: 0}) // want "i.TestExcluded is missing field A"
 
-func shouldNotPassExcludedButEnforced() {
+	// initially excluded, but enforced
 	//exhaustruct:enforce
 	_ = TestExcluded{} // want "i.TestExcluded is missing fields A, B"
 }
+
+func shouldFailOnMisappliedDirectives() {
+	// wrong directive name
+	//exhaustive:enforce
+	_ = TestExcluded{B: 0}
+}