Suggest simplifications for overzealous shifts (microsoft#59519)

Author: weswigham

src/compiler/checker.ts

@@ -39831,6 +39831,28 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
  }
  if (leftOk && rightOk) {
  checkAssignmentOperator(resultType);
+ switch (operator) {
+ case SyntaxKind.LessThanLessThanToken:
+ case SyntaxKind.LessThanLessThanEqualsToken:
+ case SyntaxKind.GreaterThanGreaterThanToken:
+ case SyntaxKind.GreaterThanGreaterThanEqualsToken:
+ case SyntaxKind.GreaterThanGreaterThanGreaterThanToken:
+ case SyntaxKind.GreaterThanGreaterThanGreaterThanEqualsToken:
+ const rhsEval = evaluate(right);
+ if (typeof rhsEval.value === "number" && Math.abs(rhsEval.value) >= 32) {
+ errorOrSuggestion(
+ isEnumMember(walkUpParenthesizedExpressions(right.parent.parent)), // elevate from suggestion to error within an enum member
+ errorNode || operatorToken,
+ Diagnostics.This_operation_can_be_simplified_This_shift_is_identical_to_0_1_2,
+ getTextOfNode(left),
+ tokenToString(operator),
+ rhsEval.value % 32,
+ );
+ }
+ break;
+ default:
+ break;
+ }
  }
  return resultType;
  }

src/compiler/diagnosticMessages.json

@@ -6420,6 +6420,10 @@
  "category": "Message",
  "code": 6806
  },
+ "This operation can be simplified. This shift is identical to `{0} {1} {2}`.": {
+ "category": "Error",
+ "code": 6807
+ },
 
  "one of:": {
  "category": "Message",

src/harness/compilerImpl.ts

@@ -241,7 +241,7 @@ export class CompilationResult {
  }
 }
 
-export function compileFiles(host: fakes.CompilerHost, rootFiles: string[] | undefined, compilerOptions: ts.CompilerOptions, typeScriptVersion?: string): CompilationResult {
+export function compileFiles(host: fakes.CompilerHost, rootFiles: string[] | undefined, compilerOptions: ts.CompilerOptions, typeScriptVersion?: string, captureSuggestions?: boolean): CompilationResult {
  if (compilerOptions.project || !rootFiles || rootFiles.length === 0) {
  const project = readProject(host.parseConfigHost, compilerOptions.project, compilerOptions);
  if (project) {
@@ -265,11 +265,17 @@ export function compileFiles(host: fakes.CompilerHost, rootFiles: string[] | und
  // and if the test is running `skipLibCheck` - an indicator that we want the tets to run quickly - skip the before/after error comparison, too
  const skipErrorComparison = ts.length(rootFiles) >= 100 || (!!compilerOptions.skipLibCheck && !!compilerOptions.declaration);
  const preProgram = !skipErrorComparison ? ts.createProgram({ rootNames: rootFiles || [], options: { ...compilerOptions, configFile: compilerOptions.configFile, traceResolution: false }, host, typeScriptVersion }) : undefined;
- const preErrors = preProgram && ts.getPreEmitDiagnostics(preProgram);
+ let preErrors = preProgram && ts.getPreEmitDiagnostics(preProgram);
+ if (preProgram && captureSuggestions) {
+ preErrors = ts.concatenate(preErrors, ts.flatMap(preProgram.getSourceFiles(), f => preProgram.getSuggestionDiagnostics(f)));
+ }
 
  const program = ts.createProgram({ rootNames: rootFiles || [], options: compilerOptions, host, typeScriptVersion });
  const emitResult = program.emit();
- const postErrors = ts.getPreEmitDiagnostics(program);
+ let postErrors = ts.getPreEmitDiagnostics(program);
+ if (captureSuggestions) {
+ postErrors = ts.concatenate(postErrors, ts.flatMap(program.getSourceFiles(), f => program.getSuggestionDiagnostics(f)));
+ }
  const longerErrors = ts.length(preErrors) > postErrors.length ? preErrors : postErrors;
  const shorterErrors = longerErrors === preErrors ? postErrors : preErrors;
  const errors = preErrors && (preErrors.length !== postErrors.length) ? [

src/harness/harnessIO.ts

@@ -282,6 +282,7 @@ export namespace Compiler {
  baselineFile?: string;
  libFiles?: string;
  noTypesAndSymbols?: boolean;
+ captureSuggestions?: boolean;
  }
 
  // Additional options not already in ts.optionDeclarations
@@ -303,6 +304,7 @@ export namespace Compiler {
  { name: "fullEmitPaths", type: "boolean", defaultValueDescription: false },
  { name: "noCheck", type: "boolean", defaultValueDescription: false },
  { name: "reportDiagnostics", type: "boolean", defaultValueDescription: false }, // used to enable error collection in `transpile` baselines
+ { name: "captureSuggestions", type: "boolean", defaultValueDescription: false }, // Adds suggestion diagnostics to error baselines
  ];
 
  let optionsIndex: Map<string, ts.CommandLineOption>;
@@ -428,7 +430,7 @@ export namespace Compiler {
 
  ts.assign(options, ts.convertToOptionsWithAbsolutePaths(options, path => ts.getNormalizedAbsolutePath(path, currentDirectory)));
  const host = new fakes.CompilerHost(fs, options);
- const result = compiler.compileFiles(host, programFileNames, options, typeScriptVersion);
+ const result = compiler.compileFiles(host, programFileNames, options, typeScriptVersion, harnessSettings?.captureSuggestions === "true");
  result.symlinks = symlinks;
  (result as CompileFilesResult).repeat = newOptions => compileFiles(inputFiles, otherFiles, { ...harnessSettings, ...newOptions }, compilerOptions, originalCurrentDirectory, symlinks);
  return result as CompileFilesResult;