[Diagnostics] Adding member subscript tailored diagnostics fixit to string literals that matches a label of labeled tuples

Author: LucianoPAlmeida

lib/Sema/CSDiagnostics.cpp

@@ -3457,7 +3457,7 @@ bool MissingMemberFailure::diagnoseForSubscriptMemberWithTupleBase() const {
     // number only literals.
     if (literal && NumericRegex.match(literal->getDigitsText())) {
       unsigned int literalValue = 0;
-      literal->getDigitsText().getAsInteger(/*Radix*/ 0, literalValue);
+      literal->getDigitsText().getAsInteger(/*Radix=*/0, literalValue);
 
       // Verify if the literal value is within the bounds of tuple elements.
       if (!literal->isNegative() &&
@@ -3473,6 +3473,27 @@ bool MissingMemberFailure::diagnoseForSubscriptMemberWithTupleBase() const {
         return true;
       }
     }
+
+    // For subscript access on tuple base types where the subscript index is a
+    // string literal expression which value matches a tuple element label,
+    // let's suggest tuple label access.
+    auto stringLiteral =
+        dyn_cast<StringLiteralExpr>(index->getSemanticsProvidingExpr());
+    if (stringLiteral && !stringLiteral->getValue().empty() &&
+        llvm::any_of(tupleType->getElements(), [&](TupleTypeElt element) {
+          return !element.getName().empty() &&
+                 element.getName().str() == stringLiteral->getValue();
+        })) {
+      llvm::SmallString<16> dotAccess;
+      llvm::raw_svector_ostream OS(dotAccess);
+      OS << "." << stringLiteral->getValue();
+
+      emitDiagnostic(
+          diag::could_not_find_subscript_member_tuple_did_you_mean_use_dot,
+          baseType, stringLiteral->getValue())
+          .fixItReplace(index->getSourceRange(), OS.str());
+      return true;
+    }
   }
 
   emitDiagnostic(diag::could_not_find_subscript_member_tuple, baseType);

test/Constraints/members.swift

@@ -675,8 +675,6 @@ let _ : [Int: Any] = [1 : .e] // expected-error {{type 'Any' has no member 'e'}}
 let _ : (Int, Any) = (1, .e) // expected-error {{type 'Any' has no member 'e'}}
 _ = (1, .e) // expected-error {{cannot infer contextual base in reference to member 'e'}}
 
-// SR-13359
-
 // SR-13359
 typealias Pair = (Int, Int)
 func testSR13359(_ pair: (Int, Int), _ alias: Pair, _ void: Void, labeled: (a: Int, b: Int)) {
@@ -713,4 +711,10 @@ func testSR13359(_ pair: (Int, Int), _ alias: Pair, _ void: Void, labeled: (a: I
   _ = labeled[0x00] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; use '.' notation instead}} {{none}}
   _ = labeled[0b00] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; use '.' notation instead}} {{none}}
 
+  // Suggesting use label access
+  _ = labeled["a"] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; did you mean to use '.a'?}} {{14-19=.a}}
+  _ = labeled["b"] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; did you mean to use '.b'?}} {{14-19=.b}}
+  _ = labeled["c"] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; use '.' notation instead}} {{none}}
+  _ = labeled[""] // expected-error {{cannot access element using subscript for tuple type '(a: Int, b: Int)'; use '.' notation instead}} {{none}}
+
 }