Fix SourceFile Visitor

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v1
       - name: Build and Test
-        run: swift test
+        run: swift test -c release
         env:
           DEVELOPER_DIR: /Applications/Xcode_11.4.app/Contents/Developer
 
@@ -28,4 +28,4 @@ jobs:
           apt-get update
           apt-get install -y libxml2-dev
       - name: Build and Test
-        run: swift test --enable-test-discovery
+        run: swift test -c release --enable-test-discovery

Sources/SwiftDoc/SourceFile.swift

@@ -89,6 +89,7 @@ public struct SourceFile: Hashable, Codable {
             visitedImports.append(`import`)
         }
 
+        @discardableResult
         func pop() -> Contextual? {
             return context.popLast()
         }
@@ -187,27 +188,33 @@ public struct SourceFile: Hashable, Codable {
         // MARK: -
 
         override func visitPost(_ node: ClassDeclSyntax) {
-            assert((pop() as? Symbol)?.api is Class)
+            let context = pop()
+            assert((context as? Symbol)?.api is Class)
         }
 
         override func visitPost(_ node: EnumDeclSyntax) {
-            assert((pop() as? Symbol)?.api is Enumeration)
+            let context = pop()
+            assert((context as? Symbol)?.api is Enumeration)
         }
 
         override func visitPost(_ node: ExtensionDeclSyntax) {
-            assert(pop() is Extension)
+            let context = pop()
+            assert(context is Extension)
         }
 
         override func visitPost(_ node: IfConfigClauseSyntax) {
-            assert(pop() is CompilationCondition)
+            let context = pop()
+            assert(context is CompilationCondition)
         }
 
         override func visitPost(_ node: ProtocolDeclSyntax) {
-            assert((pop() as? Symbol)?.api is Protocol)
+            let context = pop()
+            assert((context as? Symbol)?.api is Protocol)
         }
 
         override func visitPost(_ node: StructDeclSyntax) {
-            assert((pop() as? Symbol)?.api is Structure)
+            let context = pop()
+            assert((context as? Symbol)?.api is Structure)
         }
     }
 }

Tests/SwiftDocTests/SourceFileTests.swift

@@ -1,6 +1,6 @@
 import XCTest
 
-@testable import SwiftDoc
+import SwiftDoc
 import SwiftSemantics
 import struct SwiftSemantics.Protocol
 import SwiftSyntax