Correcting highlighting of capitals in function names.

Previously, code of the form:

    fn foo_Bar () {}

would be incorrectly highlighted, because the regex matched on word
boundaries rather than symbol boundaries. Test added.

Author: Wilfred

rust-mode-tests.el

@@ -979,6 +979,12 @@ list of substrings of `STR' each followed by its face."
    '("'\"'" font-lock-string-face
      "let" font-lock-keyword-face)))
 
+(ert-deftest font-lock-fn-contains-capital ()
+  (rust-test-font-lock
+   "fn foo_Bar() {}"
+   '("fn" font-lock-keyword-face
+     "foo_Bar" font-lock-function-name-face)))
+
 (ert-deftest font-lock-single-quote-character-literal ()
   (rust-test-font-lock
    "fn main() { let ch = '\\''; }"

rust-mode.el

@@ -359,11 +359,14 @@
     "bool"
     "str" "char"))
 
-(defconst rust-re-CamelCase "[[:upper:]][[:word:][:multibyte:]_[:digit:]]*")
+(defconst rust-re-type-or-constructor
+  (rx symbol-start
+      (group upper (0+ (any word nonascii digit "_")))
+      symbol-end))
+
 (defconst rust-re-pre-expression-operators "[-=!%&*/:<>[{(|.^;}]")
 (defun rust-re-word (inner) (concat "\\<" inner "\\>"))
 (defun rust-re-grab (inner) (concat "\\(" inner "\\)"))
-(defun rust-re-grabword (inner) (rust-re-grab (rust-re-word inner)))
 (defun rust-re-item-def (itype)
   (concat (rust-re-word itype) "[[:space:]]+" (rust-re-grab rust-re-ident)))
 
@@ -400,7 +403,7 @@
      (,(concat "'" (rust-re-grab rust-re-ident) "[^']") 1 font-lock-variable-name-face)
 
      ;; CamelCase Means Type Or Constructor
-     (,(rust-re-grabword rust-re-CamelCase) 1 font-lock-type-face)
+     (,rust-re-type-or-constructor 1 font-lock-type-face)
      )
 
    ;; Item definitions