Merge pull request #1446 from krzysztofzablocki/eh/fix-typealias-cycle

Break out of typealias cycles

Author: krzysztofzablocki

SourceryRuntime/Sources/Common/Composer/ParserResultsComposed.swift

@@ -237,8 +237,15 @@ internal struct ParserResultsComposed {
         typealiasesByNames.forEach { _, alias in
             var aliasNamesToReplace = [alias.name]
             var finalAlias = alias
+            var visitedAliasNames = Set<String>()
+            visitedAliasNames.insert(alias.name)
             while let targetAlias = typealiasesByNames[finalAlias.typeName.name] {
+                if visitedAliasNames.contains(targetAlias.name) {
+                    Log.astWarning("Detected typealias cycle while resolving '\(alias.name)' -> '\(targetAlias.name)' (type name: \(finalAlias.typeName.name)).")
+                    break
+                }
                 aliasNamesToReplace.append(targetAlias.name)
+                visitedAliasNames.insert(targetAlias.name)
                 finalAlias = targetAlias
             }
 

SourceryTests/Parsing/ComposerSpec.swift

@@ -1173,6 +1173,21 @@ class ParserComposerSpec: QuickSpec {
                               }
                         }
 
+                        it("does not loop forever when typealiases form a cycle") {
+                            let code = """
+                                       typealias Foo = Bar
+                                       typealias Bar = Foo
+                                       """
+
+                            guard let parserResult = try? makeParser(for: code).parse() else {
+                                fail("Failed to parse typealias cycle fixture")
+                                return
+                            }
+
+                            let composed = ParserResultsComposed(parserResult: parserResult)
+                            expect(composed.resolvedTypealiases.keys).to(contain("Foo", "Bar"))
+                        }
+
                         xit("follows through typealias contained in other types") {
                             let code =
                             """