More thorough consideration

Author: benjie

spec/Section 3 -- Type System.md

@@ -818,6 +818,8 @@ of rules must be adhered to by every Object type in a GraphQL schema.
          characters {"__"} (two underscores).
       2. The argument must accept a type where {IsInputType(argumentType)}
          returns {true}.
+      3. If specified, {defaultValue} must be compatible with {argumentType}
+         as per the coercion rules for that type.
 3. An object type may declare that it implements one or more unique interfaces.
 4. An object type must be a super-set of all interfaces it implements:
    1. Let this object type be {objectType}.
@@ -1466,10 +1468,12 @@ defined by the input object type and for which a value exists. The resulting map
 is constructed with the following rules:
 
 * If no value is provided for a defined input object field and that field
-  definition provides a default value, the default value should be used. If no
-  default value is provided and the input object field's type is non-null, an
-  error should be thrown. Otherwise, if the field is not required, then no entry
-  is added to the coerced unordered map.
+  definition provides a default value, the result of coercing the default value
+  according to the coercion rules of the input field type should be used (if
+  this coercion would cause an infinite loop, a query error should be thrown).
+  If no default value is provided and the input object field's type is
+  non-null, an error should be thrown. Otherwise, if the field is not required,
+  then no entry is added to the coerced unordered map.
 
 * If the value {null} was provided for an input object field, and the field's
   type is not a non-null type, an entry in the coerced unordered map is given
@@ -1526,6 +1530,8 @@ Literal Value            | Variables               | Coerced Value
       characters {"__"} (two underscores).
    3. The input field must accept a type where {IsInputType(inputFieldType)}
       returns {true}.
+   4. If specified, {defaultValue} must be compatible with {inputFieldType} as
+      per the coercion rules for that type.
 
 
 ### Input Object Extensions

spec/Section 6 -- Execution.md

@@ -89,8 +89,6 @@ CoerceVariableValues(schema, operation, variableValues):
     * Let {value} be the value provided in {variableValues} for the
       name {variableName}.
     * If {hasValue} is not {true} and {defaultValue} exists (including {null}):
-      * If {defaultValue} cannot be coerced according to the input coercion
-        rules of {variableType}, throw a query error.
       * Let {coercedDefaultValue} be the result of coercing {defaultValue} according to the
         input coercion rules of {variableType}.
       * Add an entry to {coercedValues} named {variableName} with the
@@ -590,10 +588,8 @@ CoerceArgumentValues(objectType, field, variableValues):
         name {variableName}.
     * Otherwise, let {value} be {argumentValue}.
     * If {hasValue} is not {true} and {defaultValue} exists (including {null}):
-      * If {defaultValue} cannot be coerced according to the input coercion
-        rules of {variableType}, throw a query error.
       * Let {coercedDefaultValue} be the result of coercing {defaultValue} according to the
-        input coercion rules of {variableType}.
+        input coercion rules of {argumentType}.
       * Add an entry to {coercedValues} named {argumentName} with the
         value {coercedDefaultValue}.
     * Otherwise if {argumentType} is a Non-Nullable type, and either {hasValue}