make(1): move test for the ::= modifier to varmod-assign

usr.bin/make/unit-tests/moderrs.exp

@@ -123,13 +123,6 @@ make: Unfinished modifier for FIB ('}' missing)
 make: Unfinished modifier for FIB ('}' missing)
 
 then
-mod-assign-parse:
-make: Unknown modifier ':'
-
-make: Bad modifier `:' for 
-value}
-make: Unfinished modifier for ASSIGN ('}' missing)
-
 mod-remember-parse:
 1 1 2 3 5 8 13 21 34
 make: Unknown modifier '_'

usr.bin/make/unit-tests/moderrs.mk

@@ -1,4 +1,4 @@
-# $Id: moderrs.mk,v 1.14 2020/08/09 15:15:29 rillig Exp $
+# $Id: moderrs.mk,v 1.15 2020/08/25 20:49:40 rillig Exp $
 #
 # various modifier error tests
 
@@ -20,7 +20,6 @@ all:	mod-regex-undefined-subexpression
 all:	mod-ts-parse
 all:	mod-t-parse
 all:	mod-ifelse-parse
-all:	mod-assign-parse
 all:	mod-remember-parse
 all:	mod-sysv-parse
 
@@ -164,12 +163,6 @@ mod-ifelse-parse:
 	@echo ${FIB:?then:else
 	@echo ${FIB:?then:else}
 
-mod-assign-parse:
-	@echo $@:
-	@echo ${ASSIGN::x}	# 'x' is an unknown assignment operator
-	@echo ${::=value}	# trying to set the empty variable
-	@echo ${ASSIGN::=value	# missing closing brace
-
 mod-remember-parse:
 	@echo $@:
 	@echo ${FIB:_}		# ok

usr.bin/make/unit-tests/varmod-assign.exp

@@ -10,4 +10,14 @@ mod-assign-nested: then1t1
 mod-assign-nested: else2e2
 mod-assign-nested: then3t3
 mod-assign-nested: else4e4
+make: Bad modifier `:' for 
+value}
+make: Bad modifier `:' for 
+mod-assign-empty: overwritten}
+mod-assign-empty: VAR=overwritten
+make: Unknown modifier ':'
+
+sysv:y
+make: Unfinished modifier for ASSIGN ('}' missing)
+
 exit status 0

usr.bin/make/unit-tests/varmod-assign.mk

@@ -1,10 +1,12 @@
-# $NetBSD: varmod-assign.mk,v 1.3 2020/08/25 18:59:30 rillig Exp $
+# $NetBSD: varmod-assign.mk,v 1.4 2020/08/25 20:49:40 rillig Exp $
 #
 # Tests for the obscure ::= variable modifiers, which perform variable
 # assignments during evaluation, just like the = operator in C.
 
 all:	mod-assign
 all:	mod-assign-nested
+all:	mod-assign-empty
+all:	mod-assign-parse
 
 mod-assign:
 	# The ::?= modifier applies the ?= assignment operator 3 times.
@@ -46,3 +48,24 @@ mod-assign-nested:
 	@echo $@: ${SINK4:Q}
 SINK3:=	${1:?${THEN3::=then3${IT3::=t3}}:${ELSE3::=else3${IE3::=e3}}}${THEN3}${ELSE3}${IT3}${IE3}
 SINK4:=	${0:?${THEN4::=then4${IT4::=t4}}:${ELSE4::=else4${IE4::=e4}}}${THEN4}${ELSE4}${IT4}${IE4}
+
+mod-assign-empty:
+	# Assigning to the empty variable would obviously not work since that variable
+	# is write-protected.  Therefore it is rejected early as a "bad modifier".
+	@echo ${::=value}
+	@echo $@: ${:Uvalue::=overwritten}
+
+	# The :L modifier sets the variable's value to its name.
+	# Since the name is still "VAR", assigning to that variable works.
+	@echo $@: ${VAR:L::=overwritten} VAR=${VAR}
+
+mod-assign-parse:
+	# The modifier for assignment operators starts with a ':'.
+	# An 'x' after that is an invalid modifier.
+	@echo ${ASSIGN::x}	# 'x' is an unknown assignment operator
+
+	# When parsing an assignment operator fails because the operator is
+	# incomplete, make falls back to the SysV modifier.
+	@echo ${SYSV::=sysv\:x}${SYSV::x=:y}
+
+	@echo ${ASSIGN::=value	# missing closing brace