Fix documentation generation from tasty

When running scaladoc with `-from-tasty`, documentation generation for
scala-library-bootstrapped failed with capture checking errors.

Two issues were identified and fixed:

1. Capture checking was re-running on already capture-checked code from tasty,
   causing spurious errors. Now `ccEnabled` and `ccEnabledSomewhere` return
   false when `-from-tasty` is set.

2. The `-sourcepath` setting was causing source files to be loaded, which is
   unnecessary when compiling from tasty (doc comments are stored in tasty).
   The original comment said it was needed for `Definitions#init`, but that
   mechanism (ScalaShadowingPackageClass) was removed long ago.

Author: bracevac

compiler/src/dotty/tools/dotc/config/Feature.scala

@@ -140,21 +140,27 @@ object Feature:
     || ctx.compilationUnit.knowsPureFuns
     || ccEnabled
 
-  /** Is captureChecking enabled for this compilation unit? */
+  /** Is captureChecking enabled for this compilation unit?
+   *  Disabled when compiling from tasty since capture checking was already performed.
+   */
   def ccEnabled(using Context) =
-    enabledBySetting(captureChecking)
-    || ctx.originalCompilationUnit.needsCaptureChecking
+    !ctx.settings.fromTasty.value
+    && (enabledBySetting(captureChecking)
+        || ctx.originalCompilationUnit.needsCaptureChecking)
 
   /** Is pureFunctions enabled for any of the currently compiled compilation units? */
   def pureFunsEnabledSomewhere(using Context) =
     enabledBySetting(pureFunctions)
     || ctx.run != null && ctx.run.nn.pureFunsImportEncountered
     || ccEnabledSomewhere
 
-  /** Is captureChecking enabled for any of the currently compiled compilation units? */
+  /** Is captureChecking enabled for any of the currently compiled compilation units?
+   *  Disabled when compiling from tasty since capture checking was already performed.
+   */
   def ccEnabledSomewhere(using Context) =
-    if ctx.run != null then ctx.run.nn.ccEnabledSomewhere
-    else enabledBySetting(captureChecking)
+    !ctx.settings.fromTasty.value
+    && (if ctx.run != null then ctx.run.nn.ccEnabledSomewhere
+        else enabledBySetting(captureChecking))
 
   def sourceVersionSetting(using Context): SourceVersion =
     SourceVersion.valueOf(ctx.settings.source.value)

project/Build.scala

@@ -1312,7 +1312,7 @@ object Build {
   lazy val `scala-library-bootstrapped` = project.in(file("library"))
     .enablePlugins(ScalaLibraryPlugin)
     .settings(publishSettings)
-    .settings(disableDocSetting) // TODO now produces empty JAR to satisfy Sonatype, see https://github.com/scala/scala3/issues/24434
+    //.settings(disableDocSetting) // TODO now produces empty JAR to satisfy Sonatype, see https://github.com/scala/scala3/issues/24434
     .settings(
       name          := "scala-library-bootstrapped",
       moduleName    := "scala-library",
@@ -1332,10 +1332,6 @@ object Build {
       Compile / unmanagedSourceDirectories := Seq(baseDirectory.value / "src"),
       Compile / unmanagedSourceDirectories += baseDirectory.value / "src-bootstrapped",
       Compile / scalacOptions += "-Yno-stdlib-patches",
-      Compile / scalacOptions ++= Seq(
-        // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
-        "-sourcepath", (Compile / sourceDirectories).value.map(_.getCanonicalPath).distinct.mkString(File.pathSeparator),
-      ),
       // Packaging configuration of the stdlib
       Compile / packageBin / publishArtifact := true,
       Compile / packageDoc / publishArtifact := true,