Merge pull request #885 from flashspys/detect-missing-type-colon

Detect and recover from missing type colon

Author: ahoppen

Sources/SwiftParser/Patterns.swift

@@ -120,20 +120,33 @@ extension Parser {
   /// =======
   ///
   ///     typed-pattern → pattern ':' attributes? inout? type
-  mutating func parseTypedPattern() -> (RawPatternSyntax, RawTypeAnnotationSyntax?) {
+  mutating func parseTypedPattern(allowRecoveryFromMissingColon: Bool = true) -> (RawPatternSyntax, RawTypeAnnotationSyntax?) {
     let pattern = self.parsePattern()
 
     // Now parse an optional type annotation.
-    guard let colon = self.consume(if: .colon) else {
-      return (pattern, nil)
+    let colon = self.consume(if: .colon)
+    var lookahead = self.lookahead()
+    var type: RawTypeAnnotationSyntax?
+    if let colon = colon {
+      let result = self.parseResultType()
+      type = RawTypeAnnotationSyntax(
+        colon: colon,
+        type: result,
+        arena: self.arena
+      )
+    } else if allowRecoveryFromMissingColon
+                && !self.currentToken.isAtStartOfLine
+                && lookahead.canParseType() {
+      // Recovery if the user forgot to add ':'
+      let result = self.parseResultType()
+      type = RawTypeAnnotationSyntax(
+        colon: self.missingToken(.colon, text: nil),
+        type: result,
+        arena: self.arena
+      )
     }
 
-    let result = self.parseResultType()
-    let type = RawTypeAnnotationSyntax(
-      colon: colon,
-      type: result,
-      arena: self.arena
-    )
+    
     return (pattern, type)
   }
 

Sources/SwiftParser/Statements.swift

@@ -580,7 +580,7 @@ extension Parser {
         type = nil
       }
     } else {
-      (pattern, type) = self.parseTypedPattern()
+      (pattern, type) = self.parseTypedPattern(allowRecoveryFromMissingColon: false)
     }
 
     let (unexpectedBeforeInKeyword, inKeyword) = self.expect(.inKeyword)

Tests/SwiftParserTest/Types.swift

@@ -3,6 +3,16 @@
 import XCTest
 
 final class TypeTests: XCTestCase {
+  
+  func testMissingColonInType() {
+    AssertParse(
+      """
+      var foo 1️⃣Bar = 1
+      """, diagnostics: [
+        DiagnosticSpec(message: "expected ':' in type annotation")
+      ])
+  }
+    
   func testClosureParsing() throws {
     AssertParse(
       "(a, b) -> c",