[NFC] Add helper to parse import paths in strings

Author: beccadax

include/swift/AST/Import.h

@@ -22,6 +22,7 @@
 #include "swift/AST/Identifier.h"
 #include "swift/Basic/Located.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
 
@@ -108,8 +109,11 @@ namespace detail {
     }
   };
 
+  // These shims avoid circularity between ASTContext.h and Import.h.
   ImportPathRaw ImportPathBuilder_copyToImpl(ASTContext &ctx,
                                              ImportPathRaw raw);
+  Identifier ImportPathBuilder_getIdentifierImpl(ASTContext &ctx,
+                                                 StringRef string);
 
   template<typename Subclass>
   class ImportPathBuilder {
@@ -138,6 +142,21 @@ namespace detail {
     ImportPathBuilder(Range collection)
         : scratch(collection.begin(), collection.end()) { }
 
+    /// Parses \p text into elements separated by \p separator, with identifiers
+    /// from \p ctx and invalid SourceLocs.
+    ///
+    /// \warning This is not very robust; for instance, it doesn't check the
+    /// validity of the identifiers.
+    ImportPathBuilder(ASTContext &ctx, StringRef text, char separator)
+        : scratch()
+    {
+      while (!text.empty()) {
+        StringRef next;
+        std::tie(next, text) = text.split(separator);
+        push_back(ImportPathBuilder_getIdentifierImpl(ctx, next));
+      }
+    }
+
     void push_back(const ImportPathElement &elem) { scratch.push_back(elem); }
     void push_back(Identifier name, SourceLoc loc = SourceLoc()) {
       scratch.push_back({ name, loc });

lib/AST/ASTContext.cpp

@@ -654,6 +654,12 @@ swift::detail::ImportPathBuilder_copyToImpl(ASTContext &ctx,
   return ctx.AllocateCopy(raw);
 }
 
+Identifier
+swift::detail::ImportPathBuilder_getIdentifierImpl(ASTContext &ctx,
+                                                   StringRef string) {
+  return ctx.getIdentifier(string);
+}
+
 /// Set a new stats reporter.
 void ASTContext::setStatsReporter(UnifiedStatsReporter *stats) {
   if (stats) {
@@ -1911,12 +1917,7 @@ ASTContext::getModule(ImportPath::Module ModulePath) {
 }
 
 ModuleDecl *ASTContext::getModuleByName(StringRef ModuleName) {
-  ImportPath::Module::Builder builder;
-  while (!ModuleName.empty()) {
-    StringRef SubModuleName;
-    std::tie(SubModuleName, ModuleName) = ModuleName.split('.');
-    builder.push_back(getIdentifier(SubModuleName));
-  }
+  ImportPath::Module::Builder builder(*this, ModuleName, /*separator=*/'.');
   return getModule(builder.get());
 }
 

lib/Serialization/ModuleFile.cpp

@@ -196,12 +196,12 @@ Status ModuleFile::associateWithFileContext(FileUnit *file, SourceLoc diagLoc) {
       modulePathStr = modulePathStr.slice(0, splitPoint);
     }
 
-    ImportPath::Module::Builder modulePath;
-    while (!modulePathStr.empty()) {
-      StringRef nextComponent;
-      std::tie(nextComponent, modulePathStr) = modulePathStr.split('\0');
-      modulePath.push_back(ctx.getIdentifier(nextComponent));
-      assert(!modulePath.back().Item.empty() &&
+    // TODO: Further simplification is possible by unifying scopePath above with
+    // this.
+    ImportPath::Module::Builder modulePath(ctx, modulePathStr,
+                                           /*separator=*/'\0');
+    for (const auto &elem : modulePath) {
+      assert(!elem.Item.empty() &&
              "invalid module name (submodules not yet supported)");
     }
     auto module = getModule(modulePath.get(), /*allowLoading*/true);
@@ -474,14 +474,7 @@ void ModuleFile::getImportDecls(SmallVectorImpl<Decl *> &Results) {
       if (Dep.isHeader())
         continue;
 
-      ImportPath::Builder importPath;
-
-      StringRef ModulePathStr = Dep.Core.RawPath;
-      while (!ModulePathStr.empty()) {
-        StringRef NextComponent;
-        std::tie(NextComponent, ModulePathStr) = ModulePathStr.split('\0');
-        importPath.push_back(Ctx.getIdentifier(NextComponent));
-      }
+      ImportPath::Builder importPath(Ctx, Dep.Core.RawPath, /*separator=*/'\0');
 
       if (importPath.size() == 1
           && importPath.front().Item == Ctx.StdlibModuleName)