Fix #671 - False positive in infinite range check

src/dscanner/analysis/incorrect_infinite_range.d

@@ -62,6 +62,8 @@ final class IncorrectInfiniteRangeCheck : BaseAnalyzer
 
 	override void visit(const ReturnStatement rs)
 	{
+		if (inStruct == 0 || line == size_t.max) // not within a struct yet
+			return;
 		if (!rs.expression || rs.expression.items.length != 1)
 			return;
 		UnaryExpression unary = cast(UnaryExpression) rs.expression.items[0];
@@ -82,7 +84,7 @@ private:
 	uint inStruct;
 	enum string KEY = "dscanner.suspicious.incorrect_infinite_range";
 	enum string MESSAGE = "Use `enum bool empty = false;` to define an infinite range.";
-	size_t line;
+	size_t line = size_t.max;
 	size_t column;
 }
 
@@ -123,8 +125,6 @@ class C { bool empty() { return false; } } // [warn]: %1$s
 
 }c
 			.format(IncorrectInfiniteRangeCheck.MESSAGE), sac);
-
-	stderr.writeln("Unittest for IncorrectInfiniteRangeCheck passed.");
 }
 
 // test for https://github.com/dlang-community/D-Scanner/issues/656
@@ -136,3 +136,23 @@ version(none) struct Foo
 		return;
 	}
 }
+
+unittest
+{
+	import std.stdio : stderr;
+	import dscanner.analysis.config : StaticAnalysisConfig, Check, disabledConfig;
+	import std.format : format;
+
+	StaticAnalysisConfig sac = disabledConfig();
+	sac.incorrect_infinite_range_check = Check.enabled;
+	assertAnalyzerWarnings(q{
+		enum isAllZeroBits = ()
+		{
+			if (true)
+				return true;
+			else
+				return false;
+		}();
+	}, sac);
+	stderr.writeln("Unittest for IncorrectInfiniteRangeCheck passed.");
+}