parser: Verify that "BASE" is followed by "." for base field access

http://www.freebasic.net/forum/viewtopic.php?p=207268#p207268
(cherry picked from commit b579838)

Author: dkl

changelog.txt

@@ -20,6 +20,7 @@ Version 1.02.1
 - C backend: -masm=... will now only be passed to gcc for x86[_64] targets
 - Screen didn't return an error code if it failed
 - Bad code generated for temporary variable destruction in static variable initialization: temporary strings or UDTs with destructors could be destroyed before even being initialized
+- "BASE.field" accesses in expressions (not at the start of a line) allowed any token behind "BASE" instead of the ".", for example "BASE : field", or even EOL.
 
 
 Version 1.02.0

src/compiler/parser-expr-atom.bas

@@ -335,7 +335,10 @@ private function hBaseMemberAccess _
 	( _
 		_
 	) as ASTNODE ptr
-	
+
+	'' BASE
+	assert( lexGetToken( ) = FB_TK_BASE )
+
 	var proc = parser.currproc
 
 	'' not inside a method?
@@ -359,25 +362,21 @@ private function hBaseMemberAccess _
 			return astNewCONSTi( 0 )
 		end if
 
-		'' skip BASE
+		'' BASE
 		lexSkipToken( LEXCHECK_NOPERIOD )
 
-		'' skip '.'
-		lexSkipToken()
-
-		'' (BASE '.')?
-		if( lexGetToken() <> FB_TK_BASE ) then
-			exit do
-		end if
-
 		'' '.'
-		if( lexGetLookAhead( 1 ) <> CHAR_DOT ) then
+		if( hMatch( CHAR_DOT ) = FALSE ) then
 			errReport( FB_ERRMSG_EXPECTEDPERIOD )
-			'' error recovery: skip stmt, return
 			hSkipStmt( )
 			return astNewCONSTi( 0 )
 		end if
 
+		'' (BASE '.')?
+		if( lexGetToken() <> FB_TK_BASE ) then
+			exit do
+		end if
+
 		base_ = symbGetSubtype( base_ )->udt.base
 	loop
 

tests/structs/base-access-syntax-bad-1.bas

@@ -0,0 +1,13 @@
+' TEST_MODE : COMPILE_ONLY_FAIL
+
+type A extends object
+	i1 as integer
+end type
+
+type B extends A
+	declare sub f()
+end type
+
+sub B.f()
+	print base : i1
+end sub

tests/structs/base-access-syntax-bad-2.bas

@@ -0,0 +1,14 @@
+' TEST_MODE : COMPILE_ONLY_FAIL
+
+type A extends object
+	i1 as integer
+end type
+
+type B extends A
+	declare sub f()
+end type
+
+sub B.f()
+	print base
+	i1
+end sub