Apply benjie's suggestions from code review

Co-authored-by: Benjie <[email protected]>

Author: magicmark

spec/Section 3 -- Type System.md

@@ -2217,9 +2217,7 @@ non-leaf nodes within a _schema coordinate_ cannot be found in the {schema}.
 SchemaCoordinate : Name
 
 1. Let {typeName} be the value of {Name}.
-2. Let {type} be the type in the {schema} named {typeName}.
-3. If {type} does not exist, return {null}.
-4. Return {type}.
+2. Return the type in the {schema} named {typeName}, or {null} if no such type exists.
 
 SchemaCoordinate : Name . Name
 
@@ -2228,20 +2226,14 @@ SchemaCoordinate : Name . Name
 3. Assert: {type} must exist.
 4. If {type} is an Enum type:
    1. Let {enumValueName} be the value of the second {Name}.
-   2. Let {enumValue} be the enum value of {type} named {enumValueName}.
-   3. If {enumValue} does not exist, return {null}.
-   4. Return {enumValue}.
+   2. Return the enum value of {type} named {enumValueName}, or {null} if no such value exists.
 5. Otherwise, if {type} is an Input Object type:
    1. Let {inputFieldName} be the value of the second {Name}.
-   2. Let {inputField} be the input field of {type} named {inputFieldName}.
-   3. If {inputField} does not exist, return {null}.
-   4. Return {inputField}.
+   2. Return the input field of {type} named {inputFieldName}, or {null} if no such input field exists.
 6. Otherwise:
    1. Assert: {type} must be an Object or Interface type.
    2. Let {fieldName} be the value of the second {Name}.
-   3. Let {field} be the field of {type} named {fieldName}.
-   4. If {field} does not exist, return {null}.
-   5. Return {field}.
+   3. Return the field of {type} named {fieldName}, or {null} if no such field exists.
 
 SchemaCoordinate : Name . Name ( Name : )
 
@@ -2253,27 +2245,21 @@ SchemaCoordinate : Name . Name ( Name : )
 6. Let {field} be the field of {type} named {fieldName}.
 7. Assert: {field} must exist.
 8. Let {fieldArgumentName} be the value of the third {Name}.
-9. Let {fieldArgument} be the argument of {field} named {fieldArgumentName}.
-10. If {fieldArgument} does not exist, return {null}.
-11. Return {fieldArgument}.
+9. Return the argument of {field} named {fieldArgumentName}, or {null} if no such argument exists.
 
 SchemaCoordinate : @ Name
 
 1. Let {directiveName} be the value of the first {Name}.
-2. Let {directive} be the directive in the {schema} named {directiveName}.
-3. If {directive} does not exist, return {null}.
-4. Return {directive}.
+2. Return the directive in the {schema} named {directiveName}, or {null} if no such directive exists.
 
 SchemaCoordinate : @ Name ( Name : )
 
 1. Let {directiveName} be the value of the first {Name}.
 2. Let {directive} be the directive in the {schema} named {directiveName}.
 3. Assert: {directive} must exist.
 4. Let {directiveArgumentName} be the value of the second {Name}.
-5. Let {directiveArgument} be the argument of {directive} named
-   {directiveArgumentName}.
-6. If {directiveArgument} does not exist, return {null}.
-7. Return {directiveArgument}.
+5. Return the argument of {directive} named
+   {directiveArgumentName}, or {null} if no such argument exists.
 
 **Examples**