deprecate special "inner constructor" syntax. part of #11310

Author: JeffBezanson

NEWS.md

@@ -20,6 +20,18 @@ New language features
 Language changes
 ----------------
 
+  * "Inner constructor" syntax for parametric types is deprecated. For example,
+    in this definition:
+    ```
+    type Foo{T}
+        x
+        Foo(x) = new(x)
+    end
+    ```
+    the syntax `Foo(x) = new(x)` actually defined a constructor for `Foo{T}`,
+    i.e. the case where the type parameter is specified. For clarity, this
+    definition now must be written as `Foo{T}(x) where T = new(x)`. ([#11310])
+
   * Multi-line and single-line nonstandard command literals have been added. A
     nonstandard command literal is like a nonstandard string literal, but the
     syntax uses backquotes (``` ` ```) instead of double quotes, and the

base/LineEdit.jl

@@ -1014,10 +1014,10 @@ type HistoryPrompt{T<:HistoryProvider} <: TextInterface
     hp::T
     complete
     keymap_dict::Dict{Char,Any}
-    HistoryPrompt(hp) = new(hp, EmptyCompletionProvider())
+    HistoryPrompt{T}(hp) where T<:HistoryProvider = new(hp, EmptyCompletionProvider())
 end
 
-HistoryPrompt{T<:HistoryProvider}(hp::T) = HistoryPrompt{T}(hp)
+HistoryPrompt(hp::T) where T<:HistoryProvider = HistoryPrompt{T}(hp)
 init_state(terminal, p::HistoryPrompt) = SearchState(terminal, p, true, IOBuffer(), IOBuffer())
 
 type PrefixSearchState <: ModeState
@@ -1054,10 +1054,11 @@ type PrefixHistoryPrompt{T<:HistoryProvider} <: TextInterface
     parent_prompt::Prompt
     complete
     keymap_dict::Dict{Char,Any}
-    PrefixHistoryPrompt(hp, parent_prompt) = new(hp, parent_prompt, EmptyCompletionProvider())
+    PrefixHistoryPrompt{T}(hp, parent_prompt) where T<:HistoryProvider =
+        new(hp, parent_prompt, EmptyCompletionProvider())
 end
 
-PrefixHistoryPrompt{T<:HistoryProvider}(hp::T, parent_prompt) = PrefixHistoryPrompt{T}(hp, parent_prompt)
+PrefixHistoryPrompt(hp::T, parent_prompt) where T<:HistoryProvider = PrefixHistoryPrompt{T}(hp, parent_prompt)
 init_state(terminal, p::PrefixHistoryPrompt) = PrefixSearchState(terminal, p, "", IOBuffer())
 
 write_prompt(terminal, s::PrefixSearchState) = write_prompt(terminal, s.histprompt.parent_prompt)