Add failing test cases & release snippet

docs/markdown/snippets/fstrings.md

@@ -0,0 +1,7 @@
+## Introducing format strings to the Meson language
+
+In addition to the conventional `'A string @0@ to be formatted @1@'.format(n, m)`
+method of formatting strings in the Meson DSL, there's now the additional
+`f'A string @n@ to be formatted @m@'` notation that provides a non-positional
+and clearer alternative. Meson's format strings are currently restricted to
+identity-expressions, meaning `f'format {'m' + 'e'}'` will not parse.

mesonbuild/interpreterbase.py

@@ -936,7 +936,7 @@ The result of this is undefined and will become a hard error in a future Meson r
             try:
                 val = self.variables[var]
                 if not isinstance(val, (str, int, float, bool)):
-                    raise InvalidCode(f'Identifier {var} does not name a formattable variable.')
+                    raise InvalidCode(f'Identifier "{var}" does not name a formattable variable.')
 
                 return str(val)
             except KeyError:

test cases/failing/113 invalid fstring/meson.build

@@ -0,0 +1,4 @@
+project('invalid-fstring', 'c')
+
+dict = {'key': true}
+s = f'invalid fstring: @dict@'

test cases/failing/113 invalid fstring/test.json

@@ -0,0 +1,7 @@
+{
+    "stdout": [
+        {
+            "line": "test cases/failing/113 invalid fstring/meson.build:4:0: ERROR: Identifier \"dict\" does not name a formattable variable."
+	}
+    ]
+}

test cases/failing/114 invalid fstring/meson.build

@@ -0,0 +1,3 @@
+project('invalid-fstring', 'c')
+
+z = f'invalid fstring: @foo@'

test cases/failing/114 invalid fstring/test.json

@@ -0,0 +1,7 @@
+{
+    "stdout": [
+        {
+            "line": "test cases/failing/114 invalid fstring/meson.build:3:0: ERROR: Identifier \"foo\" does not name a variable."
+	}
+    ]
+}