[CFE] Issue error when langauge version is specified too high

Specifying a language version higher than the highest supported version
(aka the default version) is an error.

Specifying a language verison in code that is higher than the one
specified in .packages is an error.

Change-Id: I44e1c8c45cef715038786dbf248925b73bd6cd7c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112240
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

Author: jensjoha

pkg/front_end/lib/src/fasta/builder/library_builder.dart

@@ -64,15 +64,19 @@ abstract class LibraryBuilder extends ModifierBuilder {
   /// Set the langauge version to a specific non-null major and minor version.
   ///
   /// If the language version has previously been explicitly set set (i.e. with
-  /// [explicit] set to true(), any subsequent call )(explicit or not) should be
+  /// [explicit] set to true), any subsequent call (explicit or not) should be
   /// ignored.
   /// Multiple calls with [explicit] set to false should be allowed though.
   ///
   /// The main idea is that the .packages file specifies a default language
-  /// version, but that the library can have source code that speicies another
+  /// version, but that the library can have source code that specifies another
   /// one which should be supported, but specifying several in code should not
   /// change anything.
-  void setLanguageVersion(int major, int minor, {bool explicit});
+  ///
+  /// [offset] and [length] refers to the offset and length of the source code
+  /// specifying the language version.
+  void setLanguageVersion(int major, int minor,
+      {int offset: 0, int length, bool explicit});
 
   @override
   Declaration get parent => null;

pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart

@@ -124,7 +124,8 @@ class DillLibraryBuilder extends LibraryBuilder {
   bool get isSynthetic => library.isSynthetic;
 
   @override
-  void setLanguageVersion(int major, int minor, {bool explicit}) {}
+  void setLanguageVersion(int major, int minor,
+      {int offset: 0, int length, bool explicit}) {}
 
   Uri get uri => library.importUri;
 

pkg/front_end/lib/src/fasta/fasta_codes_generated.dart

@@ -6570,6 +6570,34 @@ Message _withArgumentsLabelNotFound(String name) {
       arguments: {'name': name});
 }
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        int count,
+        int
+            count2)> templateLanguageVersionTooHigh = const Template<
+        Message Function(int count, int count2)>(
+    messageTemplate:
+        r"""The specified language version is too high. The highest supported language version is #count.#count2.""",
+    withArguments: _withArgumentsLanguageVersionTooHigh);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(int count, int count2)> codeLanguageVersionTooHigh =
+    const Code<Message Function(int count, int count2)>(
+  "LanguageVersionTooHigh",
+  templateLanguageVersionTooHigh,
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsLanguageVersionTooHigh(int count, int count2) {
+  if (count == null) throw 'No count provided';
+  if (count2 == null) throw 'No count provided';
+  return new Message(codeLanguageVersionTooHigh,
+      message:
+          """The specified language version is too high. The highest supported language version is ${count}.${count2}.""",
+      arguments: {'count': count, 'count2': count2});
+}
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeLibraryDirectiveNotFirst = messageLibraryDirectiveNotFirst;
 

pkg/front_end/lib/src/fasta/source/source_library_builder.dart

@@ -129,6 +129,7 @@ import '../fasta_codes.dart'
         templateIncorrectTypeArgumentQualified,
         templateIncorrectTypeArgumentQualifiedInferred,
         templateIntersectionTypeAsTypeArgument,
+        templateLanguageVersionTooHigh,
         templateLoadLibraryHidesMember,
         templateLocalDefinitionHidesExport,
         templateLocalDefinitionHidesImport,
@@ -312,6 +313,9 @@ class SourceLibraryBuilder extends LibraryBuilder {
 
   bool languageVersionExplicitlySet = false;
 
+  bool postponedProblemsIssued = false;
+  List<PostponedProblem> postponedProblems;
+
   SourceLibraryBuilder.internal(SourceLoader loader, Uri fileUri, Scope scope,
       SourceLibraryBuilder actualOrigin, Library library, Library nameOrigin)
       : this.fromScopes(loader, fileUri, new DeclarationBuilder.library(),
@@ -356,10 +360,26 @@ class SourceLibraryBuilder extends LibraryBuilder {
   }
 
   @override
-  void setLanguageVersion(int major, int minor, {bool explicit}) {
+  void setLanguageVersion(int major, int minor,
+      {int offset: 0, int length: noLength, bool explicit}) {
     if (languageVersionExplicitlySet) return;
-    library.setLanguageVersion(major, minor);
     if (explicit) languageVersionExplicitlySet = true;
+
+    // If no language version has been set, the default is used.
+    // If trying to set a langauge version that is higher than the "already-set"
+    // version it's an error.
+    if (major > library.languageVersionMajor ||
+        (major == library.languageVersionMajor &&
+            minor > library.languageVersionMinor)) {
+      addPostponedProblem(
+          templateLanguageVersionTooHigh.withArguments(
+              library.languageVersionMajor, library.languageVersionMinor),
+          offset,
+          length,
+          fileUri);
+      return;
+    }
+    library.setLanguageVersion(major, minor);
   }
 
   ConstructorReferenceBuilder addConstructorReference(Object name,
@@ -1105,6 +1125,33 @@ class SourceLibraryBuilder extends LibraryBuilder {
       ..bind(new VoidTypeBuilder(const VoidType(), this, charOffset));
   }
 
+  /// Add a problem that might not be reported immediately.
+  ///
+  /// Problems will be issued after source information has been added.
+  /// Once the problems has been issued, adding a new "postponed" problem will
+  /// be issued immediately.
+  void addPostponedProblem(
+      Message message, int charOffset, int length, Uri fileUri) {
+    if (postponedProblemsIssued) {
+      addProblem(message, charOffset, length, fileUri);
+    } else {
+      postponedProblems ??= <PostponedProblem>[];
+      postponedProblems
+          .add(new PostponedProblem(message, charOffset, length, fileUri));
+    }
+  }
+
+  void issuePostponedProblems() {
+    postponedProblemsIssued = true;
+    if (postponedProblems == null) return;
+    for (int i = 0; i < postponedProblems.length; ++i) {
+      PostponedProblem postponedProblem = postponedProblems[i];
+      addProblem(postponedProblem.message, postponedProblem.charOffset,
+          postponedProblem.length, postponedProblem.fileUri);
+    }
+    postponedProblems = null;
+  }
+
   @override
   FormattedMessage addProblem(
       Message message, int charOffset, int length, Uri fileUri,
@@ -3026,3 +3073,12 @@ Uri computeLibraryUri(Declaration declaration) {
 }
 
 String extractName(name) => name is QualifiedName ? name.name : name;
+
+class PostponedProblem {
+  final Message message;
+  final int charOffset;
+  final int length;
+  final Uri fileUri;
+
+  PostponedProblem(this.message, this.charOffset, this.length, this.fileUri);
+}

pkg/front_end/lib/src/fasta/source/source_loader.dart

@@ -214,7 +214,8 @@ class SourceLoader extends Loader {
       // TODO(jensj): What if we have several? What if it is unsupported?
       // What if the language version was already set via packages and this is
       // higher? Etc
-      library.setLanguageVersion(version.major, version.minor, explicit: true);
+      library.setLanguageVersion(version.major, version.minor,
+          offset: version.offset, length: version.length, explicit: true);
     });
     Token token = result.tokens;
     if (!suppressLexicalErrors) {
@@ -236,6 +237,7 @@ class SourceLoader extends Loader {
       target.addSourceInformation(
           importUri, library.fileUri, result.lineStarts, source);
     }
+    library.issuePostponedProblems();
     while (token is ErrorToken) {
       if (!suppressLexicalErrors) {
         ErrorToken error = token;

pkg/front_end/messages.status

@@ -334,6 +334,8 @@ InvalidVoid/part_wrapped_script1: Fail
 InvalidVoid/part_wrapped_script2: Fail
 InvalidVoid/script1: Fail
 InvalidVoid/script2: Fail
+LanguageVersionTooHigh/analyzerCode: Fail
+LanguageVersionTooHigh/part_wrapped_script: Fail # Content comes after "part of [...]" meaning it's not actually a language version specification.
 LibraryDirectiveNotFirst/part_wrapped_script1: Fail # Defining library name in the (now) part.
 LibraryDirectiveNotFirst/part_wrapped_script2: Fail
 LibraryDirectiveNotFirst/part_wrapped_script3: Fail

pkg/front_end/messages.yaml

@@ -3613,3 +3613,8 @@ CombinedMemberSignatureFailed:
       }
 
       abstract class C implements I2, I1 {}
+
+LanguageVersionTooHigh:
+  template: "The specified language version is too high. The highest supported language version is #count.#count2."
+  script: >
+    // @dart = 100.200

pkg/front_end/test/language_versioning/data/library_with_bad_version.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*error: LanguageVersionTooHigh*/
+// @dart = 3.5
+
+// If no valid language version is specified, we default to the most reason one.
+// In the tests this is hard-coded to 2.8.
+
+/*library: languageVersion=2.8*/
+
+main() {}

pkg/front_end/test/language_versioning/data/library_with_bad_version_before_good_version.dart

@@ -0,0 +1,15 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*error: LanguageVersionTooHigh*/
+// @dart = 3.5
+
+// @dart = 2.5
+
+// If the first language version specified is not a valid language version,
+// we default to the most reason one.  In the tests this is hard-coded to 2.8.
+
+/*library: languageVersion=2.8*/
+
+main() {}

pkg/front_end/test/language_versioning/data/library_with_no_version.dart

@@ -3,8 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 // If no language version is specified, and none if given in a .packages file,
-// we default to the most reason one. In the tests this is hard-coded to 2.4.
+// we default to the most reason one. In the tests this is hard-coded to 2.8.
 
-/*library: languageVersion=2.4*/
+/*library: languageVersion=2.8*/
 
 main() {}