refact: don´t allow labels declared everywhere

Labels need to be declared at the beginning of the line
(indentation allowd) and followed by a colon.

Author: boriel

src/zxbc/zxblex.py

@@ -716,7 +716,7 @@ def is_label(token) -> bool:
 
     i = token.lexpos + len(token.value)
     while i < len(input):
-        if input[i] in {"\n", ":"}:
+        if input[i] == ":":
             return True
 
         if input[i] not in {" ", "\t"}:

tests/functional/arch/zx48k/label_decl0.asm

@@ -0,0 +1,26 @@
+	org 32768
+.core.__START_PROGRAM:
+	di
+	push ix
+	push iy
+	exx
+	push hl
+	exx
+	ld hl, 0
+	add hl, sp
+	ld (.core.__CALL_BACK__), hl
+	ei
+	jp .core.__MAIN_PROGRAM__
+.core.__CALL_BACK__:
+	DEFW 0
+.core.ZXBASIC_USER_DATA:
+	; Defines USER DATA Length in bytes
+.core.ZXBASIC_USER_DATA_LEN EQU .core.ZXBASIC_USER_DATA_END - .core.ZXBASIC_USER_DATA
+	.core.__LABEL__.ZXBASIC_USER_DATA_LEN EQU .core.ZXBASIC_USER_DATA_LEN
+	.core.__LABEL__.ZXBASIC_USER_DATA EQU .core.ZXBASIC_USER_DATA
+.core.ZXBASIC_USER_DATA_END:
+.core.__MAIN_PROGRAM__:
+.LABEL._MYLABEL:
+	jp .LABEL._MYLABEL
+	;; --- end of user code ---
+	END

tests/functional/arch/zx48k/label_decl0.bas

@@ -0,0 +1,6 @@
+
+REM labels needs to be declared at the beginning of line
+REM with a trailing colon
+
+MYLABEL:
+  GOTO MYLABEL

tests/functional/arch/zx48k/label_decl1.bas

@@ -0,0 +1,5 @@
+
+REM Will fail because it lacks a trailing COLON
+
+WRONG_LABEL
+  GOTO WRONG_LABEL

tests/functional/arch/zx48k/label_decl2.bas

@@ -0,0 +1,5 @@
+
+REM will fail because labels must be declared
+REM at the begining of the line
+
+IF a > 10 THEN MYLABEL

tests/functional/arch/zx48k/label_decl3.asm

@@ -0,0 +1,89 @@
+	org 32768
+.core.__START_PROGRAM:
+	di
+	push ix
+	push iy
+	exx
+	push hl
+	exx
+	ld hl, 0
+	add hl, sp
+	ld (.core.__CALL_BACK__), hl
+	ei
+	jp .core.__MAIN_PROGRAM__
+.core.__CALL_BACK__:
+	DEFW 0
+.core.ZXBASIC_USER_DATA:
+	; Defines USER DATA Length in bytes
+.core.ZXBASIC_USER_DATA_LEN EQU .core.ZXBASIC_USER_DATA_END - .core.ZXBASIC_USER_DATA
+	.core.__LABEL__.ZXBASIC_USER_DATA_LEN EQU .core.ZXBASIC_USER_DATA_LEN
+	.core.__LABEL__.ZXBASIC_USER_DATA EQU .core.ZXBASIC_USER_DATA
+_a:
+	DEFB 00
+.core.ZXBASIC_USER_DATA_END:
+.core.__MAIN_PROGRAM__:
+	ld a, 1
+	ld hl, (_a - 1)
+	cp h
+	jp c, .LABEL._BREAK
+.LABEL.__LABEL1:
+	ld a, 8
+	call .core.__STOP
+	ld hl, 0
+	ld b, h
+	ld c, l
+.core.__END_PROGRAM:
+	di
+	ld hl, (.core.__CALL_BACK__)
+	ld sp, hl
+	exx
+	pop hl
+	exx
+	pop iy
+	pop ix
+	ei
+	ret
+.LABEL._BREAK:
+	ld hl, _a
+	inc (hl)
+	ld hl, 0
+	ld b, h
+	ld c, l
+	jp .core.__END_PROGRAM
+	;; --- end of user code ---
+#line 1 "/zxbasic/src/lib/arch/zx48k/runtime/error.asm"
+	; Simple error control routines
+; vim:ts=4:et:
+	    push namespace core
+	ERR_NR    EQU    23610    ; Error code system variable
+	; Error code definitions (as in ZX spectrum manual)
+; Set error code with:
+	;    ld a, ERROR_CODE
+	;    ld (ERR_NR), a
+	ERROR_Ok                EQU    -1
+	ERROR_SubscriptWrong    EQU     2
+	ERROR_OutOfMemory       EQU     3
+	ERROR_OutOfScreen       EQU     4
+	ERROR_NumberTooBig      EQU     5
+	ERROR_InvalidArg        EQU     9
+	ERROR_IntOutOfRange     EQU    10
+	ERROR_NonsenseInBasic   EQU    11
+	ERROR_InvalidFileName   EQU    14
+	ERROR_InvalidColour     EQU    19
+	ERROR_BreakIntoProgram  EQU    20
+	ERROR_TapeLoadingErr    EQU    26
+	; Raises error using RST #8
+__ERROR:
+	    ld (__ERROR_CODE), a
+	    rst 8
+__ERROR_CODE:
+	    nop
+	    ret
+	; Sets the error system variable, but keeps running.
+	; Usually this instruction if followed by the END intermediate instruction.
+__STOP:
+	    ld (ERR_NR), a
+	    ret
+	    pop namespace
+#line 31 "label_decl3.bas"
+	END

tests/functional/arch/zx48k/label_decl3.bas

@@ -0,0 +1,7 @@
+
+DIM a As UByte
+
+IF a > 1 THEN GOTO BREAK
+STOP
+
+BREAK: LET a = a + 1