[CS] Invalidate nested unresolved VarDecls when ignoring completion argument

Make sure we set types for any nested VarDecls in UnresolvedPatternExprs
to ensure we don't crash when attempting to solve the body.

Author: hamishknight

include/swift/AST/Expr.h

@@ -506,6 +506,10 @@ class alignas(8) Expr : public ASTAllocated<Expr> {
   /// walk into the body of it (unless it is single-expression).
   void forEachChildExpr(llvm::function_ref<Expr *(Expr *)> callback);
 
+  /// Apply the specified function to all variables referenced in any
+  /// child UnresolvedPatternExprs.
+  void forEachUnresolvedVariable(llvm::function_ref<void(VarDecl *)> f) const;
+
   /// Determine whether this expression refers to a type by name.
   ///
   /// This distinguishes static references to types, like Int, from metatype

include/swift/AST/Pattern.h

@@ -192,7 +192,7 @@ class alignas(8) Pattern : public ASTAllocated<Pattern> {
   /// Collect the set of variables referenced in the given pattern.
   void collectVariables(SmallVectorImpl<VarDecl *> &variables) const;
 
-  /// apply the specified function to all variables referenced in this
+  /// Apply the specified function to all variables referenced in this
   /// pattern.
   void forEachVariable(llvm::function_ref<void(VarDecl *)> f) const;
 

lib/AST/Pattern.cpp

@@ -192,8 +192,7 @@ namespace {
     const std::function<void(VarDecl*)> &fn;
   public:
 
-    WalkToVarDecls(const std::function<void(VarDecl*)> &fn)
-    : fn(fn) {}
+    WalkToVarDecls(const std::function<void(VarDecl*)> &fn) : fn(fn) {}
 
     /// Walk everything that's available; there shouldn't be macro expansions
     /// that matter anyway.
@@ -239,6 +238,9 @@ namespace {
   };
 } // end anonymous namespace
 
+void Expr::forEachUnresolvedVariable(llvm::function_ref<void(VarDecl *)> f) const {
+  const_cast<Expr *>(this)->walk(WalkToVarDecls(f));
+}
 
 /// apply the specified function to all variables referenced in this
 /// pattern.

lib/Sema/CSGen.cpp

@@ -4354,6 +4354,11 @@ namespace {
       auto &CS = CG.getConstraintSystem();
 
       if (CS.isArgumentIgnoredForCodeCompletion(expr)) {
+        // Make sure we invalidate any nested VarDecls to ensure the body
+        // VarDecl for a case statement still gets a type assigned.
+        expr->forEachUnresolvedVariable([&](VarDecl *VD) {
+          CS.setType(VD, ErrorType::get(CS.getASTContext()));
+        });
         CG.setTypeForArgumentIgnoredForCompletion(expr);
         return Action::SkipNode(expr);
       }

…rs/ConstraintSystem-getType-64cbd4.swift …ed/ConstraintSystem-getType-64cbd4.swiftvalidation-test/IDE/crashers/ConstraintSystem-getType-64cbd4.swift renamed to validation-test/IDE/crashers_fixed/ConstraintSystem-getType-64cbd4.swift validation-test/IDE/crashers/ConstraintSystem-getType-64cbd4.swift renamed to validation-test/IDE/crashers_fixed/ConstraintSystem-getType-64cbd4.swift

@@ -1,3 +1,3 @@
 // {"kind":"complete","signature":"swift::constraints::ConstraintSystem::getType(swift::ASTNode) const","signatureAssert":"Assertion failed: (found != NodeTypes.end() && \"Expected type to have been set!\"), function getType"}
-// RUN: not --crash %target-swift-ide-test -code-completion -batch-code-completion -skip-filecheck -code-completion-diagnostics -source-filename %s
+// RUN: %target-swift-ide-test -code-completion -batch-code-completion -skip-filecheck -code-completion-diagnostics -source-filename %s
 { switch { case let c(#^COMPLETE^# b) a