Fix reads checks for immutable variables.

test/libsolidity/syntaxTests/immutable/complex.sol

@@ -0,0 +1,8 @@
+contract A {
+  int immutable a;
+  constructor() { a = 5; }
+  function f() public { a += 7; }
+}
+
+// ----
+// TypeError 1581: (83-84): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/conditionally_initialized.sol

@@ -6,4 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 4599: (86-87): Immutable variables must be initialized unconditionally, not in an if statement.
+// TypeError 4599: (86-87): Cannot write to immutable here: Immutable variables cannot be initialized inside an if statement.

test/libsolidity/syntaxTests/immutable/ctor_indirect_initialization.sol

@@ -9,4 +9,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (119-120): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (119-120): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/ctor_modifier_args.sol

@@ -9,4 +9,4 @@ contract C {
     function f(uint a) internal pure {}
 }
 // ----
-// TypeError 1581: (59-60): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (59-60): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/ctor_modifier_initialization.sol

@@ -8,4 +8,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (102-103): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (102-103): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/decrement.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         x--;
     }
 }
 // ----
-// TypeError 7733: (67-68): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (63-64): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/delete.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         delete x;
     }
 }
 // ----
-// TypeError 7733: (74-75): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (70-71): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/delete_and_initialize.sol

@@ -0,0 +1,9 @@
+contract C {
+    uint immutable x = 3;
+    constructor() {
+        delete x;
+    }
+}
+// ----
+// TypeError 1574: (74-75): Immutable state variable already initialized.
+// TypeError 7733: (74-75): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/function_pointer_initializing.sol

@@ -10,5 +10,4 @@ contract C is B(C.f) {
     function f() internal returns(uint) { return x = 2; }
 }
 // ----
-// TypeError 1581: (200-201): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (200-201): Immutable state variable already initialized.
+// TypeError 1581: (200-201): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/increment.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         x++;
     }
 }
 // ----
-// TypeError 7733: (67-68): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (63-64): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/increment_decrement.sol

@@ -0,0 +1,11 @@
+contract C {
+  uint immutable x;
+  uint immutable y;
+  constructor() {
+    ++x;
+    --y;
+  }
+}
+// ----
+// TypeError 7733: (77-78): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (86-87): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/inheritance_ctor_argument.sol

@@ -11,4 +11,4 @@ contract C is B {
     constructor() B(y = 3) { }
 }
 // ----
-// TypeError 1581: (148-149): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (148-149): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/inheritance_ctor_inherit_specifier_argument_init.sol

@@ -10,4 +10,4 @@ contract C is B(C.y = 3) {
     uint immutable y;
 }
 // ----
-// TypeError 1581: (104-107): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (104-107): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/inheritance_wrong_ctor.sol

@@ -8,5 +8,4 @@ contract C is B {
     }
 }
 // ----
-// TypeError 7484: (88-89): Immutable variables must be initialized in the constructor of the contract they are defined in.
-// TypeError 1574: (88-89): Immutable state variable already initialized.
+// TypeError 7484: (88-89): Cannot write to immutable here: Immutable variables must be initialized in the constructor of the contract they are defined in.

test/libsolidity/syntaxTests/immutable/loop_initialized.sol

@@ -6,4 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 6672: (88-89): Immutable variables can only be initialized once, not in a while statement.
+// TypeError 6672: (88-89): Cannot write to immutable here: Immutable variables cannot be initialized inside a loop.

test/libsolidity/syntaxTests/immutable/unary.sol

@@ -0,0 +1,8 @@
+contract A {
+  int immutable a;
+  constructor() { a = 5; }
+  function f() public { --a; }
+}
+
+// ----
+// TypeError 1581: (85-86): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/writing_after_initialization.sol

@@ -6,5 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (76-77): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (76-77): Immutable state variable already initialized.
+// TypeError 1581: (76-77): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/writing_after_initialization_modifier.sol

@@ -8,5 +8,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (111-112): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (111-112): Immutable state variable already initialized.
+// TypeError 1581: (111-112): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.