reserve implements and interface as reserved words in BASIC

Author: totalspectrum

Changelog.txt

@@ -5,6 +5,7 @@ Version 6.1.6
 - Implemented flush() for FATFS files (thanks to Ada)
 - Improved some error messages
 - In C++ output, treat unknown types in prints as generic
+- Made `interface` and `implements` reserved keywords in BASIC
 - Optimized a few BASIC string expressions
 - Optimized calculating length of string literals
 - Revised BASIC use of + operator on strings

doc/basic.md

@@ -253,8 +253,10 @@ goto
 _hasmethod
 if
 import
+implements
 input
 integer
+interface
 len
 let
 lib
@@ -1347,8 +1349,7 @@ Used in a `try` statement to indicate the start of an error handling block.
 
 ### CHR$
 
-Not actually a reserved word, but a built-in function. Converts an ascii
-value to a string (so the reverse of ASC). For example:
+A special built-in function which converts an ascii value to a string (so the reverse of ASC). For example:
 ```
 print chr$(65)
 ```
@@ -2386,6 +2387,10 @@ else
 end if
 ```
 
+### IMPLEMENTS
+
+Keyword reserved for future use.
+
 ### IMPORT
 
 Keyword reserved for future use.
@@ -2480,6 +2485,10 @@ Warning: truncation will sometimes result in surprising results (e.g. `int(23.99
 
 A 32 bit signed integer type. The unsigned 32 bit integer type is `uinteger`.
 
+### INTERFACE
+
+Keyword reserved for future use.
+
 ### KILL
 
 ```

frontends/basic/basic.y

@@ -457,10 +457,12 @@ AdjustParamForByVal(AST *param)
 %token BAS_GOSUB      "gosub"
 %token BAS_HASMETHOD  "_hasmethod"
 %token BAS_IF         "if"
+%token BAS_IMPLEMENTS "implements"
 %token BAS_IMPORT     "import"
 %token BAS_INPUT      "input"
 %token BAS_CAST_INT   "int"
 %token BAS_INTEGER_KW "integer"
+%token BAS_INTERFACE  "interface"
 %token BAS_LEN        "len"
 %token BAS_LET        "let"
 %token BAS_LIB        "lib"

frontends/lexer.c

@@ -2314,10 +2314,12 @@ struct reservedword basic_keywords[] = {
     { "gosub", BAS_GOSUB },
     { "_hasmethod", BAS_HASMETHOD },
     { "if", BAS_IF },
+    { "implements", BAS_IMPLEMENTS },
     { "import", BAS_IMPORT },
     { "input", BAS_INPUT },
     { "int", BAS_CAST_INT },
     { "integer", BAS_INTEGER_KW },
+    { "interface", BAS_INTERFACE },
     { "len", BAS_LEN },
     { "let", BAS_LET },
     { "lib", BAS_LIB },