feat: empty type ascription syntax (e :) (part 2)

src/Lean/Elab/Do.lean

@@ -12,9 +12,6 @@ import Lean.Parser.Do
 -- HACK: avoid code explosion until heuristics are improved
 set_option compiler.reuse false
 
--- remove after stage0 update
-set_option quotPrecheck false
-
 namespace Lean.Elab.Term
 open Lean.Parser.Term
 open Meta

src/Lean/Parser/Term.lean

@@ -130,6 +130,9 @@ Parentheses, used for
 - Grouping expressions, e.g., `a * (b + c)`.
 - Creating tuples, e.g., `(a, b, c)` is notation for `Prod.mk a (Prod.mk b c)`.
 - Performing type ascription, e.g., `(0 : Int)` instructs Lean to process `0` as a value of type `Int`.
+  - An empty type ascription `(e :)` elaborates `e` without the expected type.
+    This is occasionally useful when Lean's heuristics for filling arguments from the expected type
+    do not yield the right result.
 - Creating `Unit.unit`, `()` is just a shorthand for `Unit.unit`.
 - Creating simple functions when combined with `·`. Here are some examples:
   - `(· + 1)` is shorthand for `fun x => x + 1`

stage0/src/stdlib_flags.h

@@ -8,7 +8,7 @@ options get_default_options() {
     // switch to `true` for ABI-breaking changes affecting meta code
     opts = opts.update({"interpreter", "prefer_native"}, false);
     // switch to `true` for changing built-in parsers used in quotations
-    opts = opts.update({"internal", "parseQuotWithCurrentStage"}, false);
+    opts = opts.update({"internal", "parseQuotWithCurrentStage"}, true);
     opts = opts.update({"pp", "rawOnError"}, true);
 #endif
     return opts;

tests/lean/StxQuot.lean.expected.out

@@ -24,8 +24,8 @@ StxQuot.lean:19:15: error: expected term
 0
 1
 "1"
-"(Term.fun\n \"fun\"\n (Term.basicFun\n  [`a._@.UnhygienicMain._hyg.1\n   (Term.paren \"(\" [`b._@.UnhygienicMain._hyg.1 [(Term.typeAscription \":\" `Nat._@.UnhygienicMain._hyg.1)]] \")\")]\n  []\n  \"=>\"\n  (num \"1\")))"
-"#[(Term.paren \"(\" [`a._@.UnhygienicMain._hyg.1 [(Term.typeAscription \":\" `Nat._@.UnhygienicMain._hyg.1)]] \")\"), `b._@.UnhygienicMain._hyg.1]"
+"(Term.fun\n \"fun\"\n (Term.basicFun\n  [`a._@.UnhygienicMain._hyg.1\n   (Term.paren \"(\" [`b._@.UnhygienicMain._hyg.1 [(Term.typeAscription \":\" [`Nat._@.UnhygienicMain._hyg.1])]] \")\")]\n  []\n  \"=>\"\n  (num \"1\")))"
+"#[(Term.paren \"(\" [`a._@.UnhygienicMain._hyg.1 [(Term.typeAscription \":\" [`Nat._@.UnhygienicMain._hyg.1])]] \")\"), `b._@.UnhygienicMain._hyg.1]"
 "`a._@.UnhygienicMain._hyg.1"
 "(Term.forall \"∀\" [(Term.hole \"_\")] [] \",\" `c._@.UnhygienicMain._hyg.1)"
 "(Term.hole \"_\")"

tests/lean/emptyTypeAscription.lean

@@ -0,0 +1,11 @@
+example : Nat := ( .zero : Nat)
+example : Nat := ( .zero : _)
+example : Nat := ( .zero :) -- fail
+example : Nat := by have' := .zero; exact this -- fail
+
+def add (x y : Nat) := x + y
+
+example (h₁ : z = x + y) (h₂ : w = z) : w = add x y := have := h₁ ▸ h₂; by exact this
+example (h₁ : z = x + y) (h₂ : w = z) : w = add x y := have := h₁ ▸ h₂; this -- fail
+example (h₁ : z = x + y) (h₂ : w = z) : w = add x y := h₁ ▸ h₂ -- fail
+example (h₁ : z = x + y) (h₂ : w = z) : w = add x y := (h₁ ▸ h₂ :)

tests/lean/emptyTypeAscription.lean.expected.out

@@ -0,0 +1,18 @@
+emptyTypeAscription.lean:3:19-3:24: error: invalid dotted identifier notation, expected type is not of the form (... → C ...) where C is a constant
+  ?m
+emptyTypeAscription.lean:4:29-4:34: error: invalid dotted identifier notation, expected type is not of the form (... → C ...) where C is a constant
+  ?m
+emptyTypeAscription.lean:9:63-9:70: error: invalid `▸` notation, expected result type of cast is 
+  w = add x y
+however, the equality 
+  h₁
+of type 
+  z = x + y
+does not contain the expected result type on either the left or the right hand side
+emptyTypeAscription.lean:10:55-10:62: error: invalid `▸` notation, expected result type of cast is 
+  w = add x y
+however, the equality 
+  h₁
+of type 
+  z = x + y
+does not contain the expected result type on either the left or the right hand side

tests/lean/interactive/hover.lean.expected.out

@@ -380,7 +380,7 @@ null
   "end": {"line": 198, "character": 32}},
  "contents":
  {"value":
-  "```lean\nId ℕ\n```\n***\nParentheses, used for\n- Grouping expressions, e.g., `a * (b + c)`.\n- Creating tuples, e.g., `(a, b, c)` is notation for `Prod.mk a (Prod.mk b c)`.\n- Performing type ascription, e.g., `(0 : Int)` instructs Lean to process `0` as a value of type `Int`.\n- Creating `Unit.unit`, `()` is just a shorthand for `Unit.unit`.\n- Creating simple functions when combined with `·`. Here are some examples:\n  - `(· + 1)` is shorthand for `fun x => x + 1`\n  - `(· + ·)` is shorthand for `fun x y => x + y`\n  - `(f · a b)` is shorthand for `fun x => f x a b`\n  - `(h (· + 1) ·)` is shorthand for `fun x => h (fun y => y + 1) x`\n",
+  "```lean\nId ℕ\n```\n***\nParentheses, used for\n- Grouping expressions, e.g., `a * (b + c)`.\n- Creating tuples, e.g., `(a, b, c)` is notation for `Prod.mk a (Prod.mk b c)`.\n- Performing type ascription, e.g., `(0 : Int)` instructs Lean to process `0` as a value of type `Int`.\n  - An empty type ascription `(e :)` elaborates `e` without the expected type.\n    This is occasionally useful when Lean's heuristics for filling arguments from the expected type\n    do not yield the right result.\n- Creating `Unit.unit`, `()` is just a shorthand for `Unit.unit`.\n- Creating simple functions when combined with `·`. Here are some examples:\n  - `(· + 1)` is shorthand for `fun x => x + 1`\n  - `(· + ·)` is shorthand for `fun x y => x + y`\n  - `(f · a b)` is shorthand for `fun x => f x a b`\n  - `(h (· + 1) ·)` is shorthand for `fun x => h (fun y => y + 1) x`\n",
   "kind": "markdown"}}
 {"textDocument": {"uri": "file://hover.lean"},
  "position": {"line": 201, "character": 8}}