Report problems through a method.

pkg/kernel/lib/verifier.dart

Index: pkg/kernel/lib/verifier.dart
diff --git a/pkg/kernel/lib/verifier.dart b/pkg/kernel/lib/verifier.dart
index b2ceb9cf7f0a9cef5248ad3a01b7cfdc0980c41e..2600f8dbf08bfd201b3e9aba0a3c377356974d45 100644
--- a/pkg/kernel/lib/verifier.dart
+++ b/pkg/kernel/lib/verifier.dart
@@ -10,6 +10,33 @@ void verifyProgram(Program program) {
   VerifyingVisitor.check(program);
 }
 
+class VerificationError {
+  final TreeNode context;
+
+  final TreeNode node;
+
+  final String details;
+
+  VerificationError(this.context, this.node, this.details);
+
+  toString() {
+    Location location;
+    try {
+      location = node?.location ?? context?.location;
+    } catch (_) {
+      // TODO(ahe): Fix the compiler instead.
+    }
+    if (location != null) {
+      String file = location.file ?? "";
+      return "$file:${location.line}:${location.column}: Verification error:"
+          " $details";
+    } else {
+      return
+          "Verification error: $details\nContext: '$context'.\nNode: '$node'.";
+    }
+  }
+}
+
 /// Checks that a kernel program is well-formed.
 ///
 /// This does not include any kind of type checking.
@@ -37,11 +64,15 @@ class VerifyingVisitor extends RecursiveVisitor {
     visitChildren(node);
   }
 
+  problem(TreeNode node, String details) {
+    throw new VerificationError(context, node, details);
+  }
+
   TreeNode enterParent(TreeNode node) {
     if (!identical(node.parent, currentParent)) {
-      throw 'Incorrect parent pointer on ${node.runtimeType} in $context. '
-          'Parent pointer is ${node.parent.runtimeType}, '
-          'actual parent is ${currentParent.runtimeType}.';
+      problem(node,
+          "Incorrect parent pointer: expected '${node.parent.runtimeType}',"
+          " but found: '${currentParent.runtimeType}'.");
     }
     var oldParent = currentParent;
     currentParent = node;
@@ -75,7 +106,8 @@ class VerifyingVisitor extends RecursiveVisitor {
 
   void declareMember(Member member) {
     if (member.transformerFlags & TransformerFlag.seenByVerifier != 0) {
-      throw '$member has been declared more than once (${member.location})';
+      problem(member.function,
+          "Member '$member' has been declared more than once.");
     }
     member.transformerFlags |= TransformerFlag.seenByVerifier;
   }
@@ -86,7 +118,7 @@ class VerifyingVisitor extends RecursiveVisitor {
 
   void declareVariable(VariableDeclaration variable) {
     if (variable.flags & VariableDeclaration.FlagInScope != 0) {
-      throw '$variable declared more than once (${variable.location})';
+      problem(variable, "Variable '$variable' declared more than once.");
     }
     variable.flags |= VariableDeclaration.FlagInScope;
     variableStack.add(variable);
@@ -100,7 +132,7 @@ class VerifyingVisitor extends RecursiveVisitor {
     for (int i = 0; i < parameters.length; ++i) {
       var parameter = parameters[i];
       if (!typeParameters.add(parameter)) {
-        throw 'Type parameter $parameter redeclared in $context';
+        problem(parameter, "Type parameter '$parameter' redeclared.");
       }
     }
   }
@@ -111,8 +143,7 @@ class VerifyingVisitor extends RecursiveVisitor {
 
   void checkVariableInScope(VariableDeclaration variable, TreeNode where) {
     if (variable.flags & VariableDeclaration.FlagInScope == 0) {
-      throw 'Variable $variable used out of scope in $context '
-          '(${where.location})';
+      problem(where, "Variable '$variable' used out of scope.");
     }
   }
 
@@ -121,7 +152,7 @@ class VerifyingVisitor extends RecursiveVisitor {
       for (var library in program.libraries) {
         for (var class_ in library.classes) {
           if (!classes.add(class_)) {
-            throw 'Class $class_ declared more than once.';
+            problem(class_, "Class '$class_' declared more than once.");
           }
         }
         library.members.forEach(declareMember);
@@ -208,8 +239,8 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitFunctionType(FunctionType node) {
     for (int i = 1; i < node.namedParameters.length; ++i) {
       if (node.namedParameters[i - 1].compareTo(node.namedParameters[i]) >= 0) {
-        throw 'Named parameters are not sorted on function type found in '
-            '$context';
+        problem(currentParent,
+            "Named parameters are not sorted on function type ($node).");
       }
     }
     declareTypeParameters(node.typeParameters);
@@ -260,13 +291,13 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitStaticGet(StaticGet node) {
     visitChildren(node);
     if (node.target == null) {
-      throw 'StaticGet without target found in $context.';
+      problem(node, "StaticGet without target.");
     }
     if (!node.target.hasGetter) {
-      throw 'StaticGet to ${node.target} without getter found in $context';
+      problem(node, "StaticGet of '${node.target}' without getter.");
     }
     if (node.target.isInstanceMember) {
-      throw 'StaticGet to ${node.target} that is not static found in $context';
+      problem(node, "StaticGet of '${node.target}' that's an instance member.");
     }
   }
 
@@ -274,34 +305,49 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitStaticSet(StaticSet node) {
     visitChildren(node);
     if (node.target == null) {
-      throw 'StaticSet without target found in $context.';
+      problem(node, "StaticSet without target.");
     }
     if (!node.target.hasSetter) {
-      throw 'StaticSet to ${node.target} without setter found in $context';
+      problem(node, "StaticSet to '${node.target}' without setter.");
     }
     if (node.target.isInstanceMember) {
-      throw 'StaticSet to ${node.target} that is not static found in $context';
+      problem(node, "StaticSet to '${node.target}' that's an instance member.");
     }
   }
 
   @override
   visitStaticInvocation(StaticInvocation node) {
+    checkTargetedInvocation(node.target, node);
+    if (node.target.isInstanceMember) {
+      problem(node,
+          "StaticInvocation of '${node.target}' that's an instance member.");
+    }
+    if (node.isConst &&
+        (!node.target.isConst || !node.target.isExternal ||
+            node.target.kind != ProcedureKind.Factory)) {
+      problem(node, "Constant StaticInvocation of '${node.target}' that isn't"
+          " a const external factory.");
+    }
+  }
+
+  void checkTargetedInvocation(Member target, InvocationExpression node) {
     visitChildren(node);
-    if (node.target == null) {
-      throw 'StaticInvocation without target found in $context.';
+    if (target == null) {
+      problem(node, "${node.runtimeType} without target.");
     }
-    if (node.target.isInstanceMember) {
-      throw 'StaticInvocation to ${node.target} that is not static found in '
-          '$context';
+    if (target.function == null) {
+      problem(node, "${node.runtimeType} without function.");
     }
-    if (!areArgumentsCompatible(node.arguments, node.target.function)) {
-      throw 'StaticInvocation with incompatible arguments to '
-          '${node.target} found in $context';
+    if (!areArgumentsCompatible(node.arguments, target.function)) {
+      problem(node,
+          "${node.runtimeType} with incompatible arguments for '${target}'.");
     }
-    if (node.arguments.types.length !=
-        node.target.function.typeParameters.length) {
-      throw 'Wrong number of type arguments provided in StaticInvocation '
-          'to ${node.target} found in $context';
+    int expectedTypeParameters = target is Constructor
+        ? target.enclosingClass.typeParameters.length
+        : target.function.typeParameters.length;
+    if (node.arguments.types.length != expectedTypeParameters) {
+      problem(node, "${node.runtimeType} with wrong number of type arguments"
+          " for '${target}'.");
     }
   }
 
@@ -309,15 +355,14 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitDirectPropertyGet(DirectPropertyGet node) {
     visitChildren(node);
     if (node.target == null) {
-      throw 'DirectPropertyGet without target found in $context.';
+      problem(node, "DirectPropertyGet without target.");
     }
     if (!node.target.hasGetter) {
-      throw 'DirectPropertyGet to ${node.target} without getter found in '
-          '$context';
+      problem(node, "DirectPropertyGet of '${node.target}' without getter.");
     }
     if (!node.target.isInstanceMember) {
-      throw 'DirectPropertyGet to ${node.target} that is static found in '
-          '$context';
+      problem(node, "DirectPropertyGet of '${node.target}' that isn't an"
+          " instance member.");
     }
   }
 
@@ -325,56 +370,33 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitDirectPropertySet(DirectPropertySet node) {
     visitChildren(node);
     if (node.target == null) {
-      throw 'DirectPropertySet without target found in $context.';
+      problem(node, "DirectPropertySet without target.");
     }
     if (!node.target.hasSetter) {
-      throw 'DirectPropertyGet to ${node.target} without setter found in '
-          '$context';
+      problem(node, "DirectPropertySet of '${node.target}' without setter.");
     }
     if (!node.target.isInstanceMember) {
-      throw 'DirectPropertySet to ${node.target} that is static found in '
-          '$context';
+      problem(node, "DirectPropertySet of '${node.target}' that is static.");
     }
   }
 
   @override
   visitDirectMethodInvocation(DirectMethodInvocation node) {
-    visitChildren(node);
-    if (node.target == null) {
-      throw 'DirectMethodInvocation without target found in $context.';
-    }
-    if (!node.target.isInstanceMember) {
-      throw 'DirectMethodInvocation to ${node.target} that is static found in '
-          '$context';
-    }
-    if (!areArgumentsCompatible(node.arguments, node.target.function)) {
-      throw 'DirectMethodInvocation with incompatible arguments to '
-          '${node.target} found in $context';
-    }
-    if (node.arguments.types.length !=
-        node.target.function.typeParameters.length) {
-      throw 'Wrong number of type arguments provided in DirectMethodInvocation '
-          'to ${node.target} found in $context';
+    checkTargetedInvocation(node.target, node);
+    if (node.receiver == null) {
+      problem(node, "DirectMethodInvocation without receiver.");
     }
   }
 
   @override
   visitConstructorInvocation(ConstructorInvocation node) {
-    visitChildren(node);
-    if (node.target == null) {
-      throw 'ConstructorInvocation without target found in $context.';
-    }
+    checkTargetedInvocation(node.target, node);
     if (node.target.enclosingClass.isAbstract) {
-      throw 'ConstructorInvocation to abstract class found in $context';
-    }
-    if (!areArgumentsCompatible(node.arguments, node.target.function)) {
-      throw 'ConstructorInvocation with incompatible arguments to '
-          '${node.target} found in $context';
+      problem(node, "ConstructorInvocation of abstract class.");
     }
-    if (node.arguments.types.length !=
-        node.target.enclosingClass.typeParameters.length) {
-      throw 'Wrong number of type arguments provided in ConstructorInvocation '
-          'to ${node.target} found in $context';
+    if (node.isConst && !node.target.isConst) {
+      problem(node, "Constant ConstructorInvocation fo '${node.target}' that"
+          " isn't const.");
     }
   }
 
@@ -400,16 +422,16 @@ class VerifyingVisitor extends RecursiveVisitor {
   @override
   defaultMemberReference(Member node) {
     if (node.transformerFlags & TransformerFlag.seenByVerifier == 0) {
-      throw 'Dangling reference to $node found in $context.\n'
-          'Parent pointer is set to ${node.parent}';
+      problem(node,
+          "Dangling reference to '$node', parent is: '${node.parent}'.");
     }
   }
 
   @override
   visitClassReference(Class node) {
     if (!classes.contains(node)) {
-      throw 'Dangling reference to $node found in $context.\n'
-          'Parent pointer is set to ${node.parent}';
+      problem(node,
+          "Dangling reference to '$node', parent is: '${node.parent}'.");
     }
   }
 
@@ -417,13 +439,12 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitTypeParameterType(TypeParameterType node) {
     var parameter = node.parameter;
     if (!typeParameters.contains(parameter)) {
-      throw 'Type parameter $parameter referenced out of scope in $context.\n'
-          'Parent pointer is set to ${parameter.parent}';
+      problem(currentParent, "Type parameter '$parameter' referenced out of"
+          " scope, parent is: '${parameter.parent}'.");
     }
     if (parameter.parent is Class && !classTypeParametersAreInScope) {
-      throw 'Type parameter $parameter referenced from static context '
-          'in $context.\n'
-          'Parent pointer is set to ${parameter.parent}';
+      problem(currentParent, "Type parameter '$parameter' referenced from"
+          " static context, parent is '${parameter.parent}'.");
     }
   }
 
@@ -431,9 +452,9 @@ class VerifyingVisitor extends RecursiveVisitor {
   visitInterfaceType(InterfaceType node) {
     node.visitChildren(this);
     if (node.typeArguments.length != node.classNode.typeParameters.length) {
-      throw 'Type $node provides ${node.typeArguments.length} type arguments '
-          'but the class declares ${node.classNode.typeParameters.length} '
-          'parameters. Found in $context.';
+      problem(currentParent, "Type $node provides ${node.typeArguments.length}"
+          " type arguments but the class declares"
+          " ${node.classNode.typeParameters.length} parameters.");
     }
   }
 }
@@ -449,9 +470,10 @@ class CheckParentPointers extends Visitor {
 
   defaultTreeNode(TreeNode node) {
     if (node.parent != parent) {
-      throw 'Parent pointer on ${node.runtimeType} '
-          'is ${node.parent.runtimeType} '
-          'but should be ${parent.runtimeType}';
+      throw new VerificationError(parent, node,
+          "Parent pointer on '${node.runtimeType}' "
+          "is '${node.parent.runtimeType}' "
+          "but should be '${parent.runtimeType}'.");
     }
     var oldParent = parent;
     parent = node;