[CS] Eagerly bind hole in recordInvalidNode

We know this is where the issue is so we can immediately bind to a hole,
ensuring we don't produce unnecessary downstream diagnostics from
things we can't infer.

Author: hamishknight

lib/Sema/CSGen.cpp

@@ -1308,14 +1308,17 @@ namespace {
       CS.setType(expr, expansionType);
     }
 
-    /// Records a fix for an invalid AST node, and returns a potential hole
-    /// type variable for it.
+    /// Records a fix for an invalid AST node, and returns a hole for it.
     Type recordInvalidNode(ASTNode node) {
       CS.recordFix(
           IgnoreInvalidASTNode::create(CS, CS.getConstraintLocator(node)));
 
-      return CS.createTypeVariable(CS.getConstraintLocator(node),
-                                   TVO_CanBindToHole);
+      // Ideally we wouldn't need a type variable here, but we don't have a
+      // suitable placeholder originator for all the cases here.
+      auto ty = CS.createTypeVariable(CS.getConstraintLocator(node),
+                                      TVO_CanBindToHole);
+      CS.recordTypeVariablesAsHoles(ty);
+      return ty;
     }
 
     virtual Type visitErrorExpr(ErrorExpr *E) {

lib/Sema/CSSimplify.cpp

@@ -6694,6 +6694,10 @@ bool ConstraintSystem::repairFailures(
   }
 
   case ConstraintLocator::Condition: {
+    // If the condition is already a hole, we're done.
+    if (lhs->isPlaceholder())
+      return true;
+
     if (repairViaOptionalUnwrap(*this, lhs, rhs, matchKind, conversionsOrFixes,
                                 locator))
       return true;

lib/Sema/ConstraintSystem.cpp

@@ -3581,12 +3581,13 @@ void constraints::simplifyLocator(ASTNode &anchor,
     }
     case ConstraintLocator::AutoclosureResult:
     case ConstraintLocator::LValueConversion:
+    case ConstraintLocator::OptionalInjection:
     case ConstraintLocator::DynamicType:
     case ConstraintLocator::UnresolvedMember:
     case ConstraintLocator::ImplicitCallAsFunction:
       // Arguments in autoclosure positions, lvalue and rvalue adjustments,
-      // unresolved members, and implicit callAsFunction references are
-      // implicit.
+      // optional injections, unresolved members, and implicit callAsFunction
+      // references are implicit.
       path = path.slice(1);
       continue;
 
@@ -3913,7 +3914,6 @@ void constraints::simplifyLocator(ASTNode &anchor,
 
     case ConstraintLocator::Witness:
     case ConstraintLocator::WrappedValue:
-    case ConstraintLocator::OptionalInjection:
     case ConstraintLocator::ImplicitlyUnwrappedDisjunctionChoice:
     case ConstraintLocator::FallbackType:
     case ConstraintLocator::KeyPathSubscriptIndex:

test/Constraints/ternary_expr.swift

@@ -59,6 +59,10 @@ _ = true ? x : 1.2 // expected-error {{result values in '? :' expression have mi
 _ = (x: true) ? true : false // expected-error {{cannot convert value of type '(x: Bool)' to expected condition type 'Bool'}}
 _ = (x: 1) ? true : false // expected-error {{cannot convert value of type '(x: Int)' to expected condition type 'Bool'}}
 
+_ = undefined ? 0 : 1 // expected-error {{cannot find 'undefined' in scope}}
+_ = [undefined] ? 0 : 1 // expected-error {{cannot find 'undefined' in scope}}
+// expected-error@-1 {{cannot convert value of type '[Element]' to expected condition type 'Bool'}}
+
 func resultBool() -> Bool { true }
 _ = resultBool ? true : false // expected-error {{function 'resultBool' was used as a property; add () to call it}} {{15-15=()}}
 

test/Parse/subscripting.swift

@@ -179,7 +179,6 @@ struct A6 {
                                      // expected-note@-2 {{did you mean}}
     get {
       return i + j // expected-error {{cannot find 'j' in scope}}
-                   // expected-error@-1 {{cannot convert return expression of type 'Int' to return type '(Int) -> Int'}}
     }
   }
 }

test/stmt/statements.swift

@@ -560,6 +560,9 @@ func bad_if() {
   if (x: false) {} // expected-error {{cannot convert value of type '(x: Bool)' to expected condition type 'Bool'}}
   if (x: 1) {} // expected-error {{cannot convert value of type '(x: Int)' to expected condition type 'Bool'}}
   if nil {} // expected-error {{'nil' is not compatible with expected condition type 'Bool'}}
+  if undefined {} // expected-error {{cannot find 'undefined' in scope}}
+  if [undefined] {} // expected-error {{cannot find 'undefined' in scope}}
+  // expected-error@-1 {{cannot convert value of type '[Element]' to expected condition type 'Bool'}}
 }
 
 // Typo correction for loop labels

test/type/protocol_composition.swift

@@ -191,11 +191,9 @@ takesP1AndP2([AnyObject & P1 & P2]())
 takesP1AndP2([Swift.AnyObject & P1 & P2]())
 takesP1AndP2([AnyObject & protocol_composition.P1 & P2]())
 takesP1AndP2([AnyObject & P1 & protocol_composition.P2]())
-takesP1AndP2([DoesNotExist & P1 & P2]()) // expected-error {{cannot find 'DoesNotExist' in scope}}
-// expected-error@-1 {{binary operator '&' cannot be applied to operands of type 'UInt8' and '(any P2).Type'}}
-// expected-error@-2 {{binary operator '&' cannot be applied to operands of type 'UInt8' and '(any P1).Type'}}
-// expected-note@-3 2 {{overloads for '&' exist with these partially matching parameter lists}}
-// expected-error@-4 {{cannot call value of non-function type '[UInt8]'}}
+takesP1AndP2([DoesNotExist & P1 & P2]())
+// expected-error@-1 {{cannot find 'DoesNotExist' in scope}}
+// expected-error@-2 {{cannot call value of non-function type '[Element]'}}
 takesP1AndP2([Swift.DoesNotExist & P1 & P2]())
 // expected-error@-1 {{module 'Swift' has no member named 'DoesNotExist'}}
 // expected-error@-2 {{cannot call value of non-function type '[Element]'}}

validation-test/compiler_crashers/ConnectedComponents-unionSets-486a70.swift renamed to validation-test/compiler_crashers_fixed/ConnectedComponents-unionSets-486a70.swift

@@ -1,4 +1,4 @@
 // {"kind":"typecheck","signature":"(anonymous namespace)::ConnectedComponents::unionSets(swift::TypeVariableType*, swift::TypeVariableType*)","signatureAssert":"Assertion failed: (validComponentCount > 0), function unionSets"}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 let b = ( c , d a {
 e b

validation-test/compiler_crashers/ConstraintGraph-computeConnectedComponents-57c387.swift renamed to validation-test/compiler_crashers_fixed/ConstraintGraph-computeConnectedComponents-57c387.swift

@@ -1,4 +1,4 @@
 // {"kind":"typecheck","signature":"swift::constraints::ConstraintGraph::computeConnectedComponents(llvm::ArrayRef<swift::TypeVariableType*>)","signatureAssert":"Assertion failed: (component != components.end()), function operator()"}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 let i = Array(... a { " ? \(i Array* )" }
                         , b 1

validation-test/compiler_crashers/ConstraintWalker-walkToExprPost-c956e0.swift renamed to validation-test/compiler_crashers_fixed/ConstraintWalker-walkToExprPost-c956e0.swift

@@ -1,5 +1,5 @@
 // {"kind":"typecheck","original":"1562769e","signature":"(anonymous namespace)::ConstraintWalker::walkToExprPost(swift::Expr*)"}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 enum c
   func d()  e {
     if let