Treat warnings more like hints (less like errors) in driver, fixes, and completions.

The presence of errors (and previously, warnings) affects what
completions are offered (or their order?) and what fixes are offered
(or their order?), and the order of re-analysis.

When unused local variables and imports etc are WARNINGS, fixes,
completions, and re-analysis should not regress.

Bug: #50796
Change-Id: If5141eec7df01f50caee5bf245c031b5a51ea590
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/291100
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

pkg/analysis_server/lib/src/services/completion/statement/statement_completion.dart

@@ -152,7 +152,7 @@ class StatementCompletionProcessor {
     }
     for (var error in statementContext.resolveResult.errors) {
       if (error.offset >= node.offset && error.offset <= node.end) {
-        if (error.errorCode is! HintCode) {
+        if (error.errorCode is! HintCode && error.errorCode is! WarningCode) {
           errors.add(error);
         }
       }

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

@@ -1739,7 +1739,9 @@ class FixProcessor extends BaseProcessor {
       }
     }
 
-    if (errorCode is LintCode || errorCode is HintCode) {
+    if (errorCode is LintCode ||
+        errorCode is HintCode ||
+        errorCode is WarningCode) {
       var generators = [
         IgnoreDiagnosticOnLine.new,
         IgnoreDiagnosticInFile.new,

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -1904,8 +1904,7 @@ class AnalysisDriver implements AnalysisDriverGeneric {
       FileState file, List<AnalysisError> errors) {
     for (AnalysisError error in errors) {
       ErrorSeverity severity = error.errorCode.errorSeverity;
-      if (severity == ErrorSeverity.ERROR ||
-          severity == ErrorSeverity.WARNING) {
+      if (severity == ErrorSeverity.ERROR) {
         file.hasErrorOrWarning = true;
         return;
       }

pkg/analyzer/test/src/dart/analysis/driver_test.dart

@@ -3308,7 +3308,7 @@ class F extends X {}
 
     allResults.clear();
 
-    // Update a.dart with changing its API signature.
+    // Update b.dart with changing its API signature.
     modifyFile(b, 'class A {}');
     driver.changeFile(b);
     await waitForIdleWithoutExceptions();