Merge pull request #1281 from ahoppen/ahoppen/missing-requirement-diagnostic

Improve diagnostic if where clause is missing a requirement

Author: ahoppen

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -776,6 +776,20 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: SameTypeRequirementSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+    if node.equalityToken.presence == .missing && node.rightTypeIdentifier.isMissingAllTokens {
+      addDiagnostic(
+        node.equalityToken,
+        .missingConformanceRequirement,
+        handledNodes: [node.equalityToken.id, node.rightTypeIdentifier.id]
+      )
+    }
+    return .visitChildren
+  }
+
   public override func visit(_ node: SourceFileSyntax) -> SyntaxVisitorContinueKind {
     if shouldSkip(node) {
       return .skipChildren

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -149,6 +149,9 @@ extension DiagnosticMessage where Self == StaticParserError {
   public static var missingColonInTernaryExpr: Self {
     .init("expected ':' after '? ...' in ternary expression")
   }
+  public static var missingConformanceRequirement: Self {
+    .init("expected ':' or '==' to indicate a conformance or same-type requirement")
+  }
   public static var misspelledAsync: Self {
     .init("expected async specifier; did you mean 'async'?")
   }

Tests/SwiftParserTest/AttributeTests.swift

@@ -43,11 +43,11 @@ final class AttributeTests: XCTestCase {
       """,
       diagnostics: [
         DiagnosticSpec(locationMarker: "1️⃣", message: "expected ':' and parameters in '@differentiable' argument", fixIts: ["insert ':' and parameters"]),
-        DiagnosticSpec(locationMarker: "2️⃣", message: "expected '=' and right-hand type in same type requirement", fixIts: ["insert '=' and right-hand type"]),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "expected ':' or '==' to indicate a conformance or same-type requirement"),
         DiagnosticSpec(locationMarker: "2️⃣", message: "expected ')' to end attribute", fixIts: ["insert ')'"]),
       ],
       fixedSource: """
-        @differentiable(reverse wrt: <#identifier#>,where T = <#type#>)
+        @differentiable(reverse wrt: <#identifier#>,where T)
         func podcastPlaybackSpeed() {
         }
         """

Tests/SwiftParserTest/DeclarationTests.swift

@@ -123,14 +123,14 @@ final class DeclarationTests: XCTestCase {
     AssertParse(
       "class T where t1️⃣",
       diagnostics: [
-        DiagnosticSpec(message: "expected '=' and right-hand type in same type requirement"),
+        DiagnosticSpec(message: "expected ':' or '==' to indicate a conformance or same-type requirement"),
         DiagnosticSpec(message: "expected member block in class"),
       ]
     )
     AssertParse(
       "class B<where g1️⃣",
       diagnostics: [
-        DiagnosticSpec(message: "expected '=' and right-hand type in same type requirement"),
+        DiagnosticSpec(message: "expected ':' or '==' to indicate a conformance or same-type requirement"),
         DiagnosticSpec(message: "expected '>' to end generic parameter clause"),
         DiagnosticSpec(message: "expected member block in class"),
       ]