Infer type of List and Map literals

compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java

Index: compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
index 700c08723921ce6f348ee43a9e89a210ce4f8d0d..b30a25f3ab72da808e0ffd6b4c7751c601a3ff84 100644
--- a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
@@ -20,8 +20,8 @@ import com.google.dart.compiler.DartCompilationPhase;
 import com.google.dart.compiler.DartCompilerContext;
 import com.google.dart.compiler.ErrorCode;
 import com.google.dart.compiler.ErrorSeverity;
-import com.google.dart.compiler.Source;
 import com.google.dart.compiler.PackageLibraryManager;
+import com.google.dart.compiler.Source;
 import com.google.dart.compiler.ast.ASTVisitor;
 import com.google.dart.compiler.ast.DartArrayAccess;
 import com.google.dart.compiler.ast.DartArrayLiteral;
@@ -163,6 +163,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
 
   @VisibleForTesting
   static class Analyzer extends ASTVisitor<Type> {
+    private final CoreTypeProvider typeProvider;
     private final DynamicType dynamicType;
     private final Type stringType;
     private final InterfaceType defaultLiteralMapType;
@@ -199,6 +200,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
     Analyzer(DartCompilerContext context, CoreTypeProvider typeProvider,
              Set<ClassElement> diagnosedAbstractClasses) {
       this.context = context;
+      this.typeProvider = typeProvider;
       this.developerModeChecks = context.getCompilerConfiguration().developerModeChecks();
       this.types = Types.getInstance(typeProvider);
       this.dynamicType = typeProvider.getDynamicType();
@@ -1826,11 +1828,13 @@ public class TypeAnalyzer implements DartCompilationPhase {
       checkAssignable(node, defaultLiteralMapType, type);
 
       // Check the map literal entries against the return type.
-      Type valueType = type.getArguments().get(1);
-      for (DartMapLiteralEntry literalEntry : node.getEntries()) {
-        boolean isValueAssignable = checkAssignable(literalEntry, typeOf(literalEntry), valueType);
-        if (developerModeChecks && !isValueAssignable) {
-          typeError(literalEntry, ResolverErrorCode.MAP_LITERAL_ELEMENT_TYPE, valueType);
+      {
+        Type valueType = type.getArguments().get(1);
+        for (DartMapLiteralEntry literalEntry : node.getEntries()) {
+          boolean isValueAssignable = checkAssignable(literalEntry, typeOf(literalEntry), valueType);
+          if (developerModeChecks && !isValueAssignable) {
+            typeError(literalEntry, ResolverErrorCode.MAP_LITERAL_ELEMENT_TYPE, valueType);
+          }
         }
       }
 
@@ -1847,6 +1851,23 @@ public class TypeAnalyzer implements DartCompilationPhase {
         }
       }
 
+      // no type arguments, try to infer
+      if (node.getTypeArguments().isEmpty()) {
+        List<Type> valueTypes = Lists.newArrayList();
+        for (DartMapLiteralEntry literalEntry : node.getEntries()) {
+          DartExpression value = literalEntry.getValue();
+          if (value != null) {
+            Type valueType = typeOf(value);
+            if (valueType != null ) {
+              valueTypes.add(valueType);
+            }
+          }
+        }
+        Type valueType = types.intersection(valueTypes);
+        valueType = Types.makeInferred(valueType);
+        return typeProvider.getMapLiteralType(stringType, valueType);
+      }
+
       return type;
     }
 
@@ -2681,6 +2702,20 @@ public class TypeAnalyzer implements DartCompilationPhase {
           }
         }
       }
+      // no type arguments, try to infer
+      if (node.getTypeArguments().isEmpty()) {
+        List<Type> elementTypes = Lists.newArrayList();
+        for (DartExpression expression : node.getExpressions()) {
+          Type elementType = expression.getType();
+          if (elementType != null ) {
+            elementTypes.add(elementType);
+          }
+        }
+        Type elementType = types.intersection(elementTypes);
+        elementType = Types.makeInferred(elementType);
+        return typeProvider.getArrayLiteralType(elementType);
+      }
+      // done
       return interfaceType;
     }