Correctly highlight types conforming to multiple protocols

Previously, the last protocol would be treated as a function call (Splash
thought it was a call with trailing closure syntax, rather than the opening
of a type definition). This patch fixes that by verifying that the code
checking for constraints inside a generic type definition is in fact looking
at a generic, rather than something else.

Sources/Splash/Grammar/SwiftGrammar.swift

@@ -257,11 +257,19 @@ private extension SwiftGrammar {
 
             // In a generic declaration, only highlight constraints
             if segment.tokens.previous.isAny(of: "<", ",") {
+                var foundOpeningBracket = false
+
                 // Since the declaration might be on another line, we have to walk
                 // backwards through all tokens until we've found enough information.
                 for token in segment.tokens.all.reversed() {
+                    if !foundOpeningBracket && token == "<" {
+                        foundOpeningBracket = true
+                    }
+
                     guard !declarationKeywords.contains(token) else {
-                        return false
+                        // If it turns out that we weren't in fact inside of a generic
+                        // declaration, (lacking "<"), then highlight the type as normal.
+                        return !foundOpeningBracket
                     }
 
                     guard !keywords.contains(token) else {

Tests/SplashTests/Tests/DeclarationTests.swift

@@ -221,6 +221,23 @@ final class DeclarationTests: SyntaxHighlighterTestCase {
         ])
     }
 
+    func testClassDeclarationWithMultipleProtocolConformances() {
+        let components = highlighter.highlight("class MyClass: ProtocolA, ProtocolB {}")
+
+        XCTAssertEqual(components, [
+            .token("class", .keyword),
+            .whitespace(" "),
+            .plainText("MyClass:"),
+            .whitespace(" "),
+            .token("ProtocolA", .type),
+            .plainText(","),
+            .whitespace(" "),
+            .token("ProtocolB", .type),
+            .whitespace(" "),
+            .plainText("{}")
+        ])
+    }
+
     func testSubclassDeclaration() {
         let components = highlighter.highlight("class ViewController: UIViewController { }")
 
@@ -616,6 +633,7 @@ extension DeclarationTests {
             ("testGenericStructDeclaration", testGenericStructDeclaration),
             ("testClassDeclaration", testClassDeclaration),
             ("testCompactClassDeclarationWithInitializer", testCompactClassDeclarationWithInitializer),
+            ("testClassDeclarationWithMultipleProtocolConformances", testClassDeclarationWithMultipleProtocolConformances),
             ("testSubclassDeclaration", testSubclassDeclaration),
             ("testProtocolDeclaration", testProtocolDeclaration),
             ("testExtensionDeclaration", testExtensionDeclaration),