[language] replace constant symbols with a constant value check function

test/results/constant variable.ans

@@ -1,7 +1,7 @@
 --# run #--
 --- error ---
-trying to change the value of constant a
+can not set a = 52; constant value check failed
 	↳ from test/tests/constant variable.ans:5:3 in call: a = 52
-	↳ from test/tests/constant variable.ans:1:1 in block: ::a = 3…
+	↳ from test/tests/constant variable.ans:1:1 in block: :a::constant = 3…
 --# saved #--
 {}

test/results/constrained variable assignement.ans

@@ -4,7 +4,7 @@
 --- text ---
 | {}"" {}"type(12, \"kg\")" {}"" |
 --- error ---
-value check failure for weigh; 32 does not satisfy $(x) type(x) == t
+can not set weigh = 32; $(x) type(x) == t value check failed
 	↳ from test/tests/constrained variable assignement.ans:9:7 in call: weigh = 32
 	↳ from test/tests/constrained variable assignement.ans:1:1 in block: :weigh::is("kg") = type(5, "kg")…
 --# saved #--

test/results/symbol alias constant.ans

@@ -5,7 +5,7 @@
 --- text ---
 | {}"d=" {}"2" {}" (2)" |
 --- error ---
-trying to change the value of constant d
+can not set d = 5; constant value check failed
 	↳ from test/tests/symbol alias constant.ans:12:3 in call: d = 5
 	↳ from test/tests/symbol alias constant.ans:1:1 in block: :l = *[1, 2, 3]…
 --# saved #--

test/tests/constant variable list.ans

@@ -1,4 +1,4 @@
-::a = *[3]
+:a::constant = *[3]
 
 |{a}
 

test/tests/constant variable.ans

@@ -1,4 +1,4 @@
-::a = 3
+:a::constant = 3
 
 {a}
 

test/tests/equality operator.ans

@@ -1,4 +1,4 @@
-::a = [1:2]
+:a::constant = [1:2]
 
 |false = {a == [5:2]}
 
@@ -6,7 +6,7 @@
 
 |true = {a == [1:2]}
 
-::b = [1,2,3]
+:b::constant = [1,2,3]
 
 |false = {b == a}
 
@@ -24,6 +24,6 @@
 
 |true = {c!to tuple == b}
 
-::d = [1,2,3]
+:d::constant = [1,2,3]
 
 |true = {d == b}

test/tests/symbol alias constant.ans

@@ -1,11 +1,11 @@
 :l = *[1,2,3]
 
-::&c => l(2)
+:&c::constant => l(2)
 
 | c={c} (2)
 | l={l} (*[1,2,3])
 
-::&d = "{l(2)}"
+:&d::constant = "{l(2)}"
 
 | d={c} (2)